Render delivery attempt detail in the event log (closes #202)

Expanding a delivery on the event log page now shows each recorded
attempt: attempt number, outcome, status code, duration, error and
response body. Previously a failure rendered as "target: failed" and
diagnosing it meant opening the per-webhook SQLite file by hand.

The response body is cut by SQLite via substr over a blob cast, the
same projection the event body uses, so an oversized stored response
never becomes a Go string. The page reports the cut with a marker.

Response bodies and errors are remote content, so both go through a
new delivery.Redactor that strips the target's own destination URL,
path, query and userinfo, plus the values of credential-shaped
request headers, before rendering. Target configuration keeps
reaching the template only as a TargetView.

A body that reaches the cap is treated as cut whether or not SQLite
is what cut it. The delivery engine stops reading a response at its
own cap, which is the same number of bytes this page renders, and
the row it writes records that cut length as the whole length, so
nothing in the row separates a response that ended at the cap from
one severed there. Such a body goes through RedactCut, which drops
any tail that is a proper prefix of a secret: the remote chooses the
padding in front of a credential it echoes, so it chooses where the
cut falls inside that credential. Its marker says the response
reached the recording limit rather than quoting a total the row does
not know.

Redactors are built from an unscoped target load. Deleting a target
only soft deletes the row while its deliveries survive, and a scoped
load would leave exactly those deliveries rendering unredacted. The
views the page lists stay scoped.

Attempt loading is chunked so the IN clause cannot exceed SQLite's
bound-parameter limit, and a chunk that fails fails the page rather
than rendering the deliveries it covered as never having run. The
page renders at most 20 attempts per delivery, counting what it
leaves out.

static/css/tailwind.css is regenerated with tailwindcss for the
utility classes the new markup uses.

README.md

@@ -127,6 +127,40 @@ empty string, and quietly withholding it would deny an endpoint that
 was asked for. The `hasMetricsAuth` field in the startup log and the
 existence of the route are the same value, so they cannot disagree.
 
+#### Single-instance lock
+
+Exactly one webhooker process may use a `DATA_DIR` at a time. Two
+processes sharing one open the same databases and each run delivery
+recovery over the same rows, so every pending delivery goes out twice —
+duplicate delivery to your endpoints, from nothing worse than an
+overlapping deploy or a double start.
+
+At startup, before anything opens a database, the process takes an
+exclusive advisory lock (`flock(2)`) on `{DATA_DIR}/webhooker.lock` and
+holds it for its lifetime. A second process pointed at the same
+directory prints a message naming it and exits non-zero:
+
+```
+webhooker: data directory is already in use by another instance: /var/lib/webhooker (/var/lib/webhooker/webhooker.lock). Only one webhooker may use a data directory: two both run delivery recovery over the same rows and both deliver
+```
+
+The lock is the kernel's, not the file's: it is released when the
+process exits, including `kill -9`, so a leftover `webhooker.lock`
+never blocks a restart and must not be deleted by hand. The file is
+also left in place on a clean shutdown, deliberately — unlinking it
+would let the next process lock a fresh inode while a third still held
+the old one.
+
+To run two webhookers on one host, give each its own `DATA_DIR`.
+
+`flock(2)` is host-local and per-inode: it arbitrates between processes
+and containers sharing a volume or bind mount on one machine, but not
+between hosts on a network filesystem, and a `DATA_DIR` inside a
+container's own writable layer is not shared with anything. On a
+filesystem that refuses `flock` outright, startup fails closed — the
+process reports the error and refuses to start rather than running
+unlocked.
+
 #### Trusted proxies
 
 `TRUSTED_PROXIES` is a comma-separated list of CIDR blocks (a bare
@@ -256,6 +290,51 @@ On first startup, webhooker creates an `admin` user
 with a randomly generated password and logs it to stdout. This password
 is only displayed once.
 
+#### What `DEBUG=true` exposes
+
+`DEBUG=true` lowers the log level to `DEBUG`, which turns on every
+statement GORM runs, the two by-design lookup misses on the
+unauthenticated routes, and the rate limiter's own rejections. It is
+meant to be safe to turn on while diagnosing a live service and safe to
+paste the output of into a bug report.
+
+What it does **not** put in the log:
+
+- **Values bound to a SQL statement.** Statements are logged with their
+  placeholders, never with the values substituted into them, at every
+  level. That is what keeps the session encryption key out of the first
+  boot's `INSERT INTO settings` and the `admin` account's Argon2id
+  password hash out of its `INSERT INTO users` — the two statements
+  that made a debug log worth stealing. It applies to every table and
+  every statement rather than to a list of tables known to hold a
+  secret, so a table added later is covered without anyone remembering
+  to add it. The cost is that a failing statement can no longer be
+  replayed from the log alone: the statement, the table, the driver
+  error and the row count are all still there, but its values have to
+  come from the database.
+  `internal/gormlog/firstboot_test.go` boots the real graph with
+  `DEBUG=true` against an empty `DATA_DIR` and asserts that neither
+  secret appears in what that boot wrote to stdout.
+  The one exception is `(*gorm.DB).Scan`, which GORM logs through its
+  own trace recorder rather than through this filter. No production
+  code path calls it, and `internal/gormlog/scan_guard_test.go` fails
+  if a non-test file adds one.
+- **Session cookies, API keys or target credentials.** None of these is
+  logged at any level.
+
+What is in the log regardless of `DEBUG`, and is not a debug-logging
+decision:
+
+- **The initial `admin` password**, in the clear, once, at `INFO`, on
+  the first boot that creates the account. That line is the only place
+  it is ever shown; the database stores the hash. A first boot's output
+  is not safe to paste anywhere until that account's password has been
+  changed.
+- **An authenticated operator's own configuration**, echoed back
+  untruncated — webhook names, target hostnames. See the logging
+  section under Security for the full list and for the per-line size
+  bound that covers unauthenticated traffic.
+
 ### Running with Docker
 
 ```bash
@@ -295,10 +374,12 @@ is both the simplest and the only complete rule:
 
 `{webhook_uuid}` is the webhook's UUID primary key in its canonical
 36-character hyphenated form, so a real filename looks like
-`events-3f2a1c9e-....db`. Nothing else is written to `DATA_DIR`, and no
-`-wal` or `-shm` files are produced (see below); a transient
-`{name}.db-journal` may exist beside a database while a write is in
-flight and is not part of the backup set.
+`events-3f2a1c9e-....db`. The only other file is `webhooker.lock`, the
+always-empty [single-instance lock](#single-instance-lock); it holds no
+state and is not part of the backup set — a copied one is stale and
+blocks nothing. No `-wal` or `-shm` files are produced (see below); a
+transient `{name}.db-journal` may exist beside a database while a write
+is in flight and is not part of the backup set either.
 
 Configuration is **not** in `DATA_DIR` — it comes from the environment
 and from a `.env` file read out of the process working directory. Back
@@ -1134,6 +1215,52 @@ delivery as `retrying` and schedules a retry timer for after the
 remaining cooldown period. This ensures no deliveries are lost — they're
 just delayed until the target is healthy again.
 
+### Metrics
+
+`/metrics` serves one Prometheus registry behind basic auth (see
+[Infrastructure Endpoints](#infrastructure-endpoints)). Alongside the
+inbound HTTP metrics recorded by the middleware, it exposes the
+delivery pipeline — the part of the service that can be failing while
+the receive side looks perfectly healthy, because it is: events are
+arriving and being stored, they are just not getting anywhere.
+
+| Metric | Type | Meaning |
+| ------ | ---- | ------- |
+| `webhooker_events_received_total` | counter | Events received and durably stored. Compare against the delivery counters on one dashboard |
+| `webhooker_delivery_attempts_total` | counter | Delivery attempts actually dispatched to a target. A delivery an open circuit breaker refused is not one: it is counted as a retry instead |
+| `webhooker_deliveries_succeeded_total` | counter | Deliveries that reached `delivered` |
+| `webhooker_deliveries_failed_total` | counter | Deliveries that failed terminally and will not be retried |
+| `webhooker_delivery_retries_total` | counter | Deliveries put back into `retrying` |
+| `webhooker_delivery_duration_seconds` | histogram | Wall time of a single dispatched delivery attempt, the same duration the attempt's `DeliveryResult` records |
+| `webhooker_deliveries_pending` | gauge | Deliveries currently in `pending` |
+| `webhooker_deliveries_retrying` | gauge | Deliveries currently in `retrying` |
+| `webhooker_circuit_breakers_open` | gauge | Circuit breakers currently open |
+
+Every delivery metric carries exactly one label, `target_type`, and
+cardinality is the whole reason for that restriction. A target type is
+one of four compile-time constants, so the label domain is bounded by
+construction; a value outside that set collapses to `unknown` rather
+than minting a series of its own. Target ids, event ids and entrypoint
+ids are deliberately not labels: they are UUIDs minted per operator
+action or per inbound request, a series is never reclaimed once it
+exists, and labelling by any of them would make `/metrics` a memory
+leak that grows with traffic.
+
+The two queue-depth gauges are counted out of the databases by a
+sampler that runs every 30 seconds for as long as the delivery engine
+does, rather than tracked as deltas alongside the status transitions: a
+delta would have to be seeded at startup from rows a previous process
+wrote, and would drift permanently on any transition that failed to
+persist.
+
+Those two gauges also publish an `unknown` series, from startup rather
+than on first occurrence. Deliveries queued against a target that has
+since been deleted are counted there: that backlog is the one nobody is
+watching, so it is the one that must not silently vanish from the
+gauge. The outcome counters move only after the status change has been
+written, so a transition the database rejected is never reported as an
+outcome that happened.
+
 ### Rate Limiting
 
 Global blanket rate limiting middleware (e.g., a per-IP throttle shared
@@ -1418,6 +1545,24 @@ and the driver error — against a smaller fixed portion than the access
 log's, and `internal/gormlog/gormlog_test.go` asserts each line against
 `MaxAccessLogLineBytes` directly rather than leaving it as arithmetic.
 
+The adapter also logs no bound value at all: it implements
+`gorm.ParamsFilter` and discards the parameters, so GORM renders the
+statement with its placeholders intact instead of substituting the
+values into it. That is a separate property from the size bound and it
+is what a bound is no substitute for — the session encryption key is 44
+base64 characters and an Argon2id hash under 100, so both fit inside
+every budget above and a truncated secret is still a secret. It holds
+on all three arms of `Trace`, including the routine one an operator
+reaches at `DEBUG`, which is the only level at which a successful
+`INSERT` is written at all. One GORM path does not consult the filter —
+`(*gorm.DB).Scan`, which records the statement through GORM's own trace
+recorder. No production code path calls it; its one caller is
+`internal/database/database_test.go:91`, whose `SELECT 1` binds
+nothing, and `internal/gormlog/scan_guard_test.go` fails if a non-test
+file calls it. `Pluck`, `Row` and `Raw` all run through the normal
+callback processor and are filtered.
+See `#### What DEBUG=true exposes` under Configuration.
+
 What that ceiling does **not** cover, stated here so the figure is not
 read as more than it is:
 
@@ -1721,7 +1866,7 @@ imports. The entry point is `cmd/webhooker/main.go`.
 ```
 webhooker/
 ├── cmd/webhooker/
-│   └── main.go               # Entry point: sets globals, wires fx
+│   └── main.go               # Entry point: sets globals, locks DATA_DIR, wires fx
 ├── internal/
 │   ├── config/
 │   │   └── config.go          # Configuration loading from environment variables
@@ -1742,6 +1887,8 @@ webhooker/
 │   │   ├── retention.go       # Retention reaper (per-webhook event expiry)
 │   │   ├── testing.go         # NewTestDatabase: wrapper for tests, no fx lifecycle
 │   │   └── webhook_db_manager.go  # Per-webhook DB lifecycle manager
+│   ├── datadir/
+│   │   └── lock.go            # Exclusive advisory lock on DATA_DIR (one instance)
 │   ├── globals/
 │   │   └── globals.go         # Build-time variables (appname, version, arch)
 │   ├── gormlog/
@@ -1759,6 +1906,7 @@ webhooker/
 │   │   ├── target_log.go      # Log target (stdout)
 │   │   ├── target_config_view.go  # Masked target config for templates
 │   │   ├── archive_sweeper.go # Periodic pruning of idle archives
+│   │   ├── queue_depth.go     # Periodic sampler behind the queue-depth gauges
 │   │   ├── url_mask.go        # Strips credentials from *url.Error
 │   │   └── ssrf.go            # SSRF prevention (IP validation, safe HTTP transport)
 │   ├── handlers/
@@ -1776,6 +1924,8 @@ webhooker/
 │   │   └── lifecycle.go       # Shared stop-hook waiter, bounded by the stop context
 │   ├── logger/
 │   │   └── logger.go          # slog setup with TTY detection
+│   ├── metrics/
+│   │   └── metrics.go         # Delivery Prometheus collectors, labelled by target type
 │   ├── middleware/
 │   │   ├── middleware.go      # Logging, CORS, Auth, Metrics, MetricsAuth, SecurityHeaders, MaxBodySize
 │   │   ├── csrf.go            # CSRF protection middleware (gorilla/csrf)

cmd/webhooker/main.go

@@ -2,11 +2,15 @@
 package main
 
 import (
+	"fmt"
+	"io"
+	"os"
 	"time"
 
 	"go.uber.org/fx"
 	"sneak.berlin/go/webhooker/internal/config"
 	"sneak.berlin/go/webhooker/internal/database"
+	"sneak.berlin/go/webhooker/internal/datadir"
 	"sneak.berlin/go/webhooker/internal/delivery"
 	"sneak.berlin/go/webhooker/internal/globals"
 	"sneak.berlin/go/webhooker/internal/handlers"
@@ -56,7 +60,32 @@ func main() {
 	globals.Appname = appname
 	globals.Version = version
 
+	os.Exit(run(os.Stderr))
+}
+
+// run takes the exclusive DATA_DIR lock, then runs the application
+// under it, and returns the process exit status.
+//
+// The lock is taken here rather than inside the fx graph because it has
+// to be held before anything opens a database, and because a refusal
+// has to reach the operator as a plain line on standard error rather
+// than as one entry in an fx failure dump. It is released by the defer
+// on a clean shutdown, and by the kernel closing the descriptor on any
+// other exit — including the one fx performs itself when a start or
+// stop hook fails, which skips deferred calls.
+func run(stderr io.Writer) int {
+	lock, err := datadir.Acquire(config.DataDir())
+	if err != nil {
+		_, _ = fmt.Fprintf(stderr, "%s: %v\n", appname, err)
+
+		return 1
+	}
+
+	defer func() { _ = lock.Release() }()
+
 	newApp().Run()
+
+	return 0
 }
 
 // newApp builds the application graph. It is separate from main so

cmd/webhooker/main_test.go

@@ -1,10 +1,13 @@
 package main
 
 import (
+	"bytes"
 	"testing"
 	"time"
 
+	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
+	"sneak.berlin/go/webhooker/internal/datadir"
 	"sneak.berlin/go/webhooker/internal/server"
 )
 
@@ -33,6 +36,38 @@ func TestNewApp_StopTimeout(t *testing.T) {
 	require.Less(t, got, dockerStopGrace)
 }
 
+// TestRunRefusesLockedDataDir pins what an operator's second start
+// does. The entry point must refuse before it builds the fx graph —
+// nothing may open a database in a DATA_DIR another process holds —
+// and must exit non-zero with a message naming the directory rather
+// than starting a second delivery engine over the same rows.
+//
+// flock(2) locks descriptors independently, so holding the lock here
+// is the same denial a separate process gets; internal/datadir pins
+// that property and covers the real two-process case.
+func TestRunRefusesLockedDataDir(t *testing.T) {
+	dir := t.TempDir()
+	t.Setenv("DATA_DIR", dir)
+
+	lock, err := datadir.Acquire(dir)
+	require.NoError(t, err)
+
+	defer func() { _ = lock.Release() }()
+
+	var stderr bytes.Buffer
+
+	code := run(&stderr)
+
+	require.Equal(
+		t, 1, code, "a second instance must exit non-zero",
+	)
+	assert.Contains(
+		t, stderr.String(), dir,
+		"the refusal must name the directory",
+	)
+	assert.Contains(t, stderr.String(), "another instance")
+}
+
 // tailHeadroom is the slack the fx stop budget must keep beyond the
 // server stop hook. The hooks that run after the server — the
 // delivery engine, the healthcheck, the webhook DB manager and the

go.mod

@@ -8,13 +8,15 @@ require (
 	github.com/go-chi/chi v1.5.5
 	github.com/go-chi/cors v1.2.1
 	github.com/go-chi/httprate v0.15.0
+	github.com/gofrs/flock v0.13.0
 	github.com/google/uuid v1.6.0
 	github.com/gorilla/csrf v1.7.3
 	github.com/gorilla/sessions v1.4.0
 	github.com/joho/godotenv v1.5.1
 	github.com/prometheus/client_golang v1.18.0
+	github.com/prometheus/client_model v0.5.0
 	github.com/slok/go-http-metrics v0.11.0
-	github.com/stretchr/testify v1.8.4
+	github.com/stretchr/testify v1.11.1
 	go.uber.org/fx v1.20.1
 	golang.org/x/crypto v0.38.0
 	gopkg.in/yaml.v3 v3.0.1
@@ -38,7 +40,6 @@ require (
 	github.com/mattn/go-sqlite3 v1.14.17 // indirect
 	github.com/matttproud/golang_protobuf_extensions/v2 v2.0.0 // indirect
 	github.com/pmezard/go-difflib v1.0.1-0.20181226105442-5d4384ee4fb2 // indirect
-	github.com/prometheus/client_model v0.5.0 // indirect
 	github.com/prometheus/common v0.45.0 // indirect
 	github.com/prometheus/procfs v0.12.0 // indirect
 	github.com/remyoudompheng/bigfft v0.0.0-20230129092748-24d4a6f8daec // indirect
@@ -49,7 +50,7 @@ require (
 	go.uber.org/zap v1.23.0 // indirect
 	golang.org/x/mod v0.17.0 // indirect
 	golang.org/x/sync v0.14.0 // indirect
-	golang.org/x/sys v0.33.0 // indirect
+	golang.org/x/sys v0.37.0 // indirect
 	golang.org/x/text v0.25.0 // indirect
 	golang.org/x/tools v0.21.1-0.20240508182429-e35e4ccd0d2d // indirect
 	google.golang.org/protobuf v1.31.0 // indirect

go.sum

@@ -23,6 +23,8 @@ github.com/go-chi/httprate v0.15.0 h1:j54xcWV9KGmPf/X4H32/aTH+wBlrvxL7P+SdnRqxh5
 github.com/go-chi/httprate v0.15.0/go.mod h1:rzGHhVrsBn3IMLYDOZQsSU4fJNWcjui4fWKJcCId1R4=
 github.com/go-errors/errors v1.4.2 h1:J6MZopCL4uSllY1OfXM374weqZFFItUbrImctkmUxIA=
 github.com/go-errors/errors v1.4.2/go.mod h1:sIVyrIiJhuEF+Pj9Ebtd6P/rEYROXFi3BopGUQ5a5Og=
+github.com/gofrs/flock v0.13.0 h1:95JolYOvGMqeH31+FC7D2+uULf6mG61mEZ/A8dRYMzw=
+github.com/gofrs/flock v0.13.0/go.mod h1:jxeyy9R1auM5S6JYDBhDt+E2TCo7DkratH4Pgi8P+Z0=
 github.com/golang/protobuf v1.5.0/go.mod h1:FsONVRAS9T7sI+LIUmWTfcYkHO4aIWwzhcaSAoJOfIk=
 github.com/google/go-cmp v0.5.5/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=
 github.com/google/go-cmp v0.6.0 h1:ofyhxvXcZhMsU5ulbFiLKl/XBFqE1GSq7atu8tAmTRI=
@@ -81,11 +83,11 @@ github.com/rogpeppe/go-internal v1.10.0/go.mod h1:UQnix2H7Ngw/k4C5ijL5+65zddjncj
 github.com/slok/go-http-metrics v0.11.0 h1:ABJUpekCZSkQT1wQrFvS4kGbhea/w6ndFJaWJeh3zL0=
 github.com/slok/go-http-metrics v0.11.0/go.mod h1:ZGKeYG1ET6TEJpQx18BqAJAvxw9jBAZXCHU7bWQqqAc=
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
-github.com/stretchr/objx v0.5.1 h1:4VhoImhV/Bm0ToFkXFi8hXNXwpDRZ/ynw3amt82mzq0=
-github.com/stretchr/objx v0.5.1/go.mod h1:/iHQpkQwBD6DLUmQ4pE+s1TXdob1mORJ4/UFdrifcy0=
+github.com/stretchr/objx v0.5.2 h1:xuMeJ0Sdp5ZMRXx/aWO6RZxdr3beISkG5/G/aIRr3pY=
+github.com/stretchr/objx v0.5.2/go.mod h1:FRsXN1f5AsAjCGJKqEizvkpNtU+EGNCLh3NxZ/8L+MA=
 github.com/stretchr/testify v1.3.0/go.mod h1:M5WIy9Dh21IEIfnGCwXGc5bZfKNJtfHm1UVUgZn+9EI=
-github.com/stretchr/testify v1.8.4 h1:CcVxjf3Q8PM0mHUKJCdn+eZZtm5yQwehR5yeSVQQcUk=
-github.com/stretchr/testify v1.8.4/go.mod h1:sz/lmYIOXD/1dqDmKjjqLyZ2RngseejIcXlSw2iwfAo=
+github.com/stretchr/testify v1.11.1 h1:7s2iGBzp5EwR7/aIZr8ao5+dra3wiQyKjjFuvgVKu7U=
+github.com/stretchr/testify v1.11.1/go.mod h1:wZwfW3scLgRK+23gO65QZefKpKQRnfz6sD981Nm4B6U=
 github.com/zeebo/assert v1.3.0 h1:g7C04CbJuIDKNPFHmsk4hwZDO5O+kntRxzaUoNXj+IQ=
 github.com/zeebo/assert v1.3.0/go.mod h1:Pq9JiuJQpG8JLJdtkwrJESF0Foym2/D9XMU5ciN/wJ0=
 github.com/zeebo/xxh3 v1.0.2 h1:xZmwmqxHZA8AI603jOQ0tMqmBr9lPeFwGg6d+xy9DC0=
@@ -109,8 +111,8 @@ golang.org/x/mod v0.17.0/go.mod h1:hTbmBsO62+eylJbnUtE2MGJUyE7QWk4xUqPFrRgJ+7c=
 golang.org/x/sync v0.14.0 h1:woo0S4Yywslg6hp4eUFjTVOyKt0RookbpAHG4c1HmhQ=
 golang.org/x/sync v0.14.0/go.mod h1:1dzgHSNfp02xaA81J2MS99Qcpr2w7fw1gpm99rleRqA=
 golang.org/x/sys v0.6.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
-golang.org/x/sys v0.33.0 h1:q3i8TbbEz+JRD9ywIRlyRAQbM0qF7hu24q3teo2hbuw=
-golang.org/x/sys v0.33.0/go.mod h1:BJP2sWEmIv4KK5OTEluFJCKSidICx8ciO85XgH3Ak8k=
+golang.org/x/sys v0.37.0 h1:fdNQudmxPjkdUTPnLn5mdQv7Zwvbvpaxqs831goi9kQ=
+golang.org/x/sys v0.37.0/go.mod h1:OgkHotnGiDImocRcuBABYBEXf8A9a87e/uXjp9XT3ks=
 golang.org/x/text v0.25.0 h1:qVyWApTSYLk/drJRO5mDlNYskwQznZmkpV2c8q9zls4=
 golang.org/x/text v0.25.0/go.mod h1:WEdwpYrmk1qmdHvhkSTNPm3app7v4rsT8F2UD6+VHIA=
 golang.org/x/tools v0.21.1-0.20240508182429-e35e4ccd0d2d h1:vU5i/LfpvrRCpgM/VPfJLg5KjxD3E+hfT1SH+d9zLwg=

internal/config/config.go

@@ -26,6 +26,10 @@ const (
 	// EnvironmentProd represents production environment.
 	EnvironmentProd = "prod"
 
+	// DefaultDataDir is where all SQLite databases live when DATA_DIR
+	// is unset. The same default applies in every environment.
+	DefaultDataDir = "/var/lib/webhooker"
+
 	// defaultPort is the default HTTP listen port.
 	defaultPort = 8080
 
@@ -159,6 +163,19 @@ func envString(key string) string {
 	return os.Getenv(key)
 }
 
+// DataDir resolves DATA_DIR, applying DefaultDataDir when it is unset
+// or empty. It is exported so that entry points which must act on the
+// data directory before the fx graph exists — taking the exclusive
+// directory lock, above all — resolve it exactly as Config does.
+func DataDir() string {
+	dir := envString("DATA_DIR")
+	if dir == "" {
+		return DefaultDataDir
+	}
+
+	return dir
+}
+
 // envBool returns the value of the named environment variable
 // parsed as a boolean. Returns defaultValue if not set. If the
 // variable is set but cannot be parsed, it returns a wrapped error
@@ -461,7 +478,7 @@ func loadFromEnv() (*Config, error) {
 	}
 
 	return &Config{
-		DataDir:                envString("DATA_DIR"),
+		DataDir:                DataDir(),
 		Debug:                  debug,
 		MaintenanceMode:        maintenanceMode,
 		Environment:            environment,
@@ -539,14 +556,6 @@ func New(lc fx.Lifecycle, params ConfigParams) (*Config, error) {
 	s.log = log
 	s.params = &params
 
-	// Set default DataDir. All SQLite databases (main application
-	// DB and per-webhook event DBs) live here. The same default is
-	// used regardless of environment; override with DATA_DIR if
-	// needed.
-	if s.DataDir == "" {
-		s.DataDir = "/var/lib/webhooker"
-	}
-
 	if s.Debug {
 		params.Logger.EnableDebugLogging()
 	}

internal/config/config_test.go

@@ -424,6 +424,36 @@ func TestDefaultDataDir(t *testing.T) {
 	}
 }
 
+// TestDataDirHelper pins the exported resolver against the value
+// Config carries. The entry point takes the DATA_DIR lock through the
+// helper before the fx graph exists, so the two disagreeing would mean
+// locking one directory and writing to another.
+func TestDataDirHelper(t *testing.T) {
+	for _, set := range []string{"", "/tmp/webhooker-datadir-helper"} {
+		name := "set"
+		if set == "" {
+			name = "unset"
+		}
+
+		t.Run(name, func(t *testing.T) {
+			// Cannot use t.Parallel() here because t.Setenv
+			// is incompatible with parallel subtests.
+			if set == "" {
+				require.NoError(t, os.Unsetenv("DATA_DIR"))
+			} else {
+				t.Setenv("DATA_DIR", set)
+			}
+
+			expected := set
+			if expected == "" {
+				expected = config.DefaultDataDir
+			}
+
+			assert.Equal(t, expected, config.DataDir())
+		})
+	}
+}
+
 func TestReceiverRateLimit(t *testing.T) {
 	tests := []struct {
 		name        string

internal/datadir/lock.go

@@ -0,0 +1,126 @@
+// Package datadir guards exclusive access to the directory holding
+// every SQLite database webhooker writes.
+//
+// Two processes sharing a DATA_DIR each open the same per-webhook
+// event databases and each run delivery recovery over the same rows,
+// so every pending delivery goes out twice. SQLite's own locking does
+// not prevent that: both writers are serialised correctly and both
+// deliver. The only thing that prevents it is refusing to be the
+// second process.
+//
+// The lock lives here rather than in the server's fx graph so that any
+// entry point which touches DATA_DIR — the server, or a CLI
+// subcommand that must not operate on a live deployment's data — takes
+// it the same way.
+package datadir
+
+import (
+	"errors"
+	"fmt"
+	"os"
+	"path/filepath"
+
+	"github.com/gofrs/flock"
+)
+
+// LockFileName is the advisory lock file created inside DATA_DIR. Its
+// contents are never read: the lock is the flock(2) held on the open
+// descriptor, not the file's existence, so a leftover file from a
+// process that was killed with SIGKILL blocks nothing.
+const LockFileName = "webhooker.lock"
+
+// dirPerm is the mode Acquire creates DATA_DIR with. It matches what
+// internal/database uses, since whichever runs first creates it.
+const dirPerm = 0o750
+
+// ErrLocked reports that another live process holds the data
+// directory. Callers that need to know whether a deployment is running
+// — rather than merely failing to start — test for this with
+// errors.Is.
+var ErrLocked = errors.New(
+	"data directory is already in use by another instance",
+)
+
+// ErrNoDir reports that Acquire was given an empty directory.
+var ErrNoDir = errors.New("no data directory given")
+
+// Lock is a held exclusive advisory lock on a data directory. It is
+// valid only while the process that took it lives: the kernel drops it
+// when the descriptor closes, whether that is Release, a normal exit,
+// or a SIGKILL.
+type Lock struct {
+	dir  string
+	file *flock.Flock
+}
+
+// Acquire takes the exclusive advisory lock on dir, creating dir if it
+// does not exist. It never waits: if another process holds the lock it
+// returns an error wrapping ErrLocked and naming dir.
+//
+// The returned Lock must be held for as long as the caller intends to
+// use dir.
+func Acquire(dir string) (*Lock, error) {
+	if dir == "" {
+		return nil, ErrNoDir
+	}
+
+	err := os.MkdirAll(dir, dirPerm)
+	if err != nil {
+		return nil, fmt.Errorf(
+			"creating data directory %s: %w", dir, err,
+		)
+	}
+
+	path := filepath.Join(dir, LockFileName)
+	fl := flock.New(path)
+
+	held, err := fl.TryLock()
+	if err != nil {
+		return nil, fmt.Errorf(
+			"locking data directory %s: %w", dir, err,
+		)
+	}
+
+	if !held {
+		// A no-op on flock v0.13.0, which closes its own descriptor on
+		// a failed TryLock; kept so no version can leak one.
+		_ = fl.Close()
+
+		return nil, fmt.Errorf(
+			"%w: %s (%s). Only one webhooker may use a data "+
+				"directory: two both run delivery recovery over the "+
+				"same rows and both deliver",
+			ErrLocked, dir, path,
+		)
+	}
+
+	return &Lock{dir: dir, file: fl}, nil
+}
+
+// Dir returns the locked directory.
+func (l *Lock) Dir() string {
+	return l.dir
+}
+
+// Path returns the lock file backing the lock.
+func (l *Lock) Path() string {
+	return l.file.Path()
+}
+
+// Release drops the lock and closes the descriptor. It is safe to call
+// more than once.
+//
+// The lock file is deliberately left on disk. Unlinking it would let
+// the next process create and lock a fresh inode while a third still
+// holds the old one, which is the one outcome this package exists to
+// prevent.
+func (l *Lock) Release() error {
+	err := l.file.Unlock()
+	if err != nil {
+		return fmt.Errorf(
+			"releasing lock on data directory %s: %w", l.dir, err,
+		)
+	}
+
+	return nil
+}

internal/datadir/lock_test.go

@@ -0,0 +1,250 @@
+package datadir_test
+
+import (
+	"bufio"
+	"fmt"
+	"io"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"strings"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"sneak.berlin/go/webhooker/internal/datadir"
+)
+
+// holderEnv names the directory the re-executed test binary should
+// lock and hold. When it is unset the child test does nothing, so an
+// ordinary run is unaffected.
+const holderEnv = "WEBHOOKER_DATADIR_LOCK_HOLDER"
+
+// holderReadyPrefix labels the child's one-line report that it holds
+// the lock, so the parent can find it among the testing package's own
+// output on the same descriptor.
+const holderReadyPrefix = "DATADIR-LOCK-HELD "
+
+// holderReadyTimeout bounds the wait for the child to take the lock.
+// It only has to cover process start on a loaded shared host.
+const holderReadyTimeout = 60 * time.Second
+
+// holderHold is how long the child keeps the lock if nothing kills it.
+// A sleep rather than a bare block, so the runtime's deadlock detector
+// has a pending timer and the child cannot outlive a killed test run
+// by more than this.
+const holderHold = 10 * time.Minute
+
+// TestLockHolder is the child half of the two-process tests below. It
+// takes the lock on the directory named by holderEnv, reports the lock
+// file on standard output, and then holds it until it is killed.
+func TestLockHolder(t *testing.T) {
+	t.Parallel()
+
+	dir := os.Getenv(holderEnv)
+	if dir == "" {
+		return
+	}
+
+	lock, err := datadir.Acquire(dir)
+	require.NoError(t, err)
+
+	// Written to the descriptor directly: the parent reads fd 1, not
+	// the testing package's buffered report.
+	_, err = fmt.Fprintf(
+		os.Stdout, "%s%s\n", holderReadyPrefix, lock.Path(),
+	)
+	require.NoError(t, err)
+
+	time.Sleep(holderHold)
+}
+
+// startHolder re-executes this test binary as a separate process that
+// takes and holds the lock on dir, and returns once that process
+// actually holds it. The child is killed when the test ends.
+func startHolder(t *testing.T, dir string) *exec.Cmd {
+	t.Helper()
+
+	//nolint:gosec // Re-executing this test binary, with a fixed arg.
+	cmd := exec.CommandContext(
+		t.Context(), os.Args[0], "-test.run", "^TestLockHolder$",
+	)
+
+	cmd.Env = append(os.Environ(), holderEnv+"="+dir)
+	cmd.Stderr = os.Stderr
+
+	stdout, err := cmd.StdoutPipe()
+	require.NoError(t, err)
+	require.NoError(t, cmd.Start())
+
+	t.Cleanup(func() {
+		_ = cmd.Process.Kill()
+		_ = cmd.Wait()
+	})
+
+	ready := make(chan string, 1)
+
+	go func() {
+		scanner := bufio.NewScanner(stdout)
+		for scanner.Scan() {
+			after, found := strings.CutPrefix(
+				scanner.Text(), holderReadyPrefix,
+			)
+			if found {
+				ready <- after
+
+				break
+			}
+		}
+
+		close(ready)
+
+		// Keep draining so the child never blocks on a full pipe.
+		_, _ = io.Copy(io.Discard, stdout)
+	}()
+
+	select {
+	case path, ok := <-ready:
+		require.True(
+			t, ok, "holder exited without taking the lock",
+		)
+		require.Equal(t, filepath.Join(dir, datadir.LockFileName), path)
+	case <-time.After(holderReadyTimeout):
+		t.Fatal("timed out waiting for the holder to take the lock")
+	}
+
+	return cmd
+}
+
+// TestSecondInstanceRefused is the regression test for the duplicate
+// delivery this package exists to prevent: a real second process
+// pointed at a data directory a live process already holds must be
+// refused, with an error that names the directory.
+func TestSecondInstanceRefused(t *testing.T) {
+	t.Parallel()
+
+	dir := t.TempDir()
+
+	startHolder(t, dir)
+
+	lock, err := datadir.Acquire(dir)
+
+	require.Error(t, err, "the second instance took the lock too")
+	require.Nil(t, lock)
+	require.ErrorIs(
+		t, err, datadir.ErrLocked,
+		"the refusal must be distinguishable from any other failure",
+	)
+	assert.Contains(
+		t, err.Error(), dir,
+		"the refusal must name the directory it is about",
+	)
+}
+
+// TestRestartAfterHardKill is the other half of the regression: a
+// process killed with SIGKILL runs no cleanup and leaves its lock file
+// behind, and the next start must not be blocked by it. This is what a
+// pidfile would get wrong; the kernel drops a flock when the
+// descriptor closes, however the process died.
+func TestRestartAfterHardKill(t *testing.T) {
+	t.Parallel()
+
+	dir := t.TempDir()
+
+	holder := startHolder(t, dir)
+
+	require.NoError(t, holder.Process.Kill())
+
+	// Wait for the kill to have actually happened. Re-acquiring while
+	// the corpse still holds a descriptor would be a race, and would
+	// make this test pass or fail on scheduling.
+	_ = holder.Wait()
+
+	require.FileExists(
+		t, filepath.Join(dir, datadir.LockFileName),
+		"the stale lock file is what must not block the restart",
+	)
+
+	lock, err := datadir.Acquire(dir)
+	require.NoError(
+		t, err, "a hard-killed instance must not block the next start",
+	)
+
+	require.NoError(t, lock.Release())
+}
+
+// TestSecondFdInSameProcessRefused pins the flock(2) property the
+// tests in cmd/webhooker rely on: descriptors are locked
+// independently, so a second acquisition is denied even when it comes
+// from the process that already holds the lock.
+func TestSecondFdInSameProcessRefused(t *testing.T) {
+	t.Parallel()
+
+	dir := t.TempDir()
+
+	first, err := datadir.Acquire(dir)
+	require.NoError(t, err)
+
+	defer func() { _ = first.Release() }()
+
+	_, err = datadir.Acquire(dir)
+	require.ErrorIs(t, err, datadir.ErrLocked)
+}
+
+// TestReleaseAllowsReacquire covers the clean-shutdown path: the lock
+// is released on exit, so a restart is not blocked by the previous
+// run.
+func TestReleaseAllowsReacquire(t *testing.T) {
+	t.Parallel()
+
+	dir := t.TempDir()
+
+	first, err := datadir.Acquire(dir)
+	require.NoError(t, err)
+	require.NoError(t, first.Release())
+
+	second, err := datadir.Acquire(dir)
+	require.NoError(t, err)
+	require.NoError(t, second.Release())
+}
+
+// TestAcquireCreatesDataDir covers a first start against a DATA_DIR
+// that does not exist yet, which is the normal case for a fresh
+// deployment: the lock is taken before anything else creates it.
+func TestAcquireCreatesDataDir(t *testing.T) {
+	t.Parallel()
+
+	dir := filepath.Join(t.TempDir(), "nested", "data")
+
+	lock, err := datadir.Acquire(dir)
+	require.NoError(t, err)
+
+	defer func() { _ = lock.Release() }()
+
+	assert.Equal(t, dir, lock.Dir())
+	assert.FileExists(t, filepath.Join(dir, datadir.LockFileName))
+}
+
+// TestAcquireEmptyDir rejects an empty directory rather than locking
+// the process's working directory.
+func TestAcquireEmptyDir(t *testing.T) {
+	t.Parallel()
+
+	_, err := datadir.Acquire("")
+	require.ErrorIs(t, err, datadir.ErrNoDir)
+}
+
+// TestAcquireUnusableDir reports an unusable DATA_DIR clearly, naming
+// it, instead of failing later and deeper.
+func TestAcquireUnusableDir(t *testing.T) {
+	t.Parallel()
+
+	file := filepath.Join(t.TempDir(), "not-a-directory")
+	require.NoError(t, os.WriteFile(file, nil, 0o600))
+
+	_, err := datadir.Acquire(file)
+
+	require.Error(t, err)
+	assert.Contains(t, err.Error(), file)
+}

internal/delivery/engine.go

@@ -15,6 +15,7 @@ import (
 	"sneak.berlin/go/webhooker/internal/database"
 	"sneak.berlin/go/webhooker/internal/lifecycle"
 	"sneak.berlin/go/webhooker/internal/logger"
+	"sneak.berlin/go/webhooker/internal/metrics"
 )
 
 const (
@@ -139,6 +140,12 @@ type Engine struct {
 	retryCh    chan Task
 	workers    int
 
+	// mtr is the delivery metric set. Production wires the
+	// process-wide one; a test can substitute a set registered on
+	// a private registry so its assertions are not disturbed by
+	// deliveries other tests are making at the same time.
+	mtr *metrics.Set
+
 	// targets maps each target type to its implementation.
 	targets map[database.TargetType]Target
 
@@ -164,6 +171,7 @@ func New(
 		deliveryCh: make(chan Task, deliveryChannelSize),
 		retryCh:    make(chan Task, retryChannelSize),
 		workers:    defaultWorkers,
+		mtr:        metrics.Default(),
 	}
 
 	e.initTargets(&http.Client{
@@ -283,6 +291,10 @@ func (e *Engine) start() {
 
 	go e.retrySweep(ctx)
 
+	e.wg.Add(1)
+
+	go e.queueDepthSampler(ctx)
+
 	e.log.Info(
 		"delivery engine started",
 		"workers", e.workers,
@@ -837,8 +849,15 @@ func (e *Engine) failUnretryableRetry(
 		0,
 	)
 
+	// The type is passed rather than assigned onto d: the delivery
+	// is loaded here without its target relation, and populating
+	// d.Target would make GORM's SaveBeforeAssociations upsert the
+	// whole target row — plaintext config, which for a slack target
+	// is the credential — into the per-webhook event database. See
+	// https://git.eeqj.de/sneak/webhooker/issues/206.
 	e.updateDeliveryStatus(
-		webhookDB, d, database.DeliveryStatusFailed,
+		webhookDB, d, target.Type,
+		database.DeliveryStatusFailed,
 	)
 }
 
@@ -859,7 +878,8 @@ func (e *Engine) processDelivery(
 		)
 
 		e.updateDeliveryStatus(
-			webhookDB, d, database.DeliveryStatusFailed,
+			webhookDB, d, d.Target.Type,
+			database.DeliveryStatusFailed,
 		)
 
 		return
@@ -868,6 +888,24 @@ func (e *Engine) processDelivery(
 	target.Deliver(ctx, webhookDB, d, task, e)
 }
 
+// observeAttempt counts one delivery attempt that was actually
+// dispatched to a target, and records how long it took.
+//
+// It is called from the dispatch paths rather than from around
+// Target.Deliver, because Deliver is also entered for deliveries
+// that never reach the wire: a delivery an open circuit breaker
+// refuses sends nothing, records no DeliveryResult, and is
+// rescheduled. Counting those would climb the attempts counter with
+// no traffic behind it and fill the duration histogram with
+// microsecond samples, which would make the delivery-duration
+// quantiles improve during exactly the outage they exist to reveal.
+func (e *Engine) observeAttempt(
+	t database.TargetType, dur time.Duration,
+) {
+	e.mtr.DeliveryAttempted(t)
+	e.mtr.ObserveDeliveryDuration(t, dur)
+}
+
 // recordResult persists a DeliveryResult row describing a
 // single attempt. It is a cross-target helper the targets
 // call.
@@ -901,10 +939,22 @@ func (e *Engine) recordResult(
 }
 
 // updateDeliveryStatus persists a new status for a delivery.
-// It is a cross-target helper the targets call.
+// It is a cross-target helper the targets call, and therefore the
+// single point where a delivery's outcome — delivered, terminally
+// failed, or put back into retry — is counted.
+//
+// The target type is a parameter rather than read off d.Target
+// because one caller — failUnretryableRetry — deliberately holds a
+// delivery loaded without its target relation, and must keep it that
+// way: a populated d.Target makes GORM upsert the target row, config
+// and all, into the per-webhook database.
+//
+// The counter moves only after the row is written, so a transition
+// the database rejected is not claimed as an outcome that happened.
 func (e *Engine) updateDeliveryStatus(
 	webhookDB *gorm.DB,
 	d *database.Delivery,
+	targetType database.TargetType,
 	status database.DeliveryStatus,
 ) {
 	err := webhookDB.Model(d).
@@ -916,7 +966,11 @@ func (e *Engine) updateDeliveryStatus(
 			"status", status,
 			"error", err,
 		)
+
+		return
 	}
+
+	e.mtr.DeliveryStatusChanged(targetType, status)
 }
 
 func truncate(s string, maxLen int) string {

internal/delivery/engine_integration_test.go

@@ -886,6 +886,82 @@ func TestSweepSingleRetry_TypeNoLongerRetries(
 	)
 }
 
+// TestFailUnretryableRetry_WritesNoTargetRow proves the
+// orphaned-retry terminal path leaves no target row — and so no
+// plaintext target config — in the per-webhook event database.
+//
+// That path loads the delivery without its Target relation on
+// purpose. Populating d.Target makes GORM's SaveBeforeAssociations
+// upsert the whole target row on the status UPDATE, which for a slack
+// target writes the incoming-webhook credential into events-*.db.
+// See https://git.eeqj.de/sneak/webhooker/issues/206.
+func TestFailUnretryableRetry_WritesNoTargetRow(
+	t *testing.T,
+) {
+	t.Parallel()
+
+	s := newISetup(t)
+
+	iCreateWebhook(
+		t, s.MainDB, s.WebhookID, "no-target-row",
+	)
+
+	targetID := uuid.New().String()
+
+	// A Slack incoming-webhook URL: the target config IS the
+	// credential, which is what makes a leaked target row a
+	// disclosure rather than a curiosity.
+	hookURL := "https://hooks.slack.com/services/T00/B00/x"
+
+	iCreateTarget(t, s.MainDB, targetID,
+		s.WebhookID, "credential-bearing",
+		database.TargetTypeLog, iHTTPConfig(hookURL), 5,
+	)
+
+	event := iSeedEvent(
+		t, s.WebhookDB, s.WebhookID, `{"orphaned":"retry"}`,
+	)
+
+	d := iSeedDelivery(
+		t, s.WebhookDB, event.ID, targetID,
+		database.DeliveryStatusRetrying,
+	)
+
+	iSeedFailedResult(t, s.WebhookDB, d.ID)
+
+	s.Engine.ExportSweepWebhookRetries(
+		context.Background(), s.WebhookID,
+	)
+
+	iAssertStatus(t, s.WebhookDB, d.ID,
+		database.DeliveryStatusFailed,
+	)
+
+	// The table exists in the per-webhook database because GORM
+	// migrates the Delivery relation's model alongside it. It must
+	// stay empty.
+	var targetRows int64
+
+	require.NoError(t, s.WebhookDB.
+		Table("targets").
+		Count(&targetRows).Error)
+
+	assert.Zero(t, targetRows,
+		"orphaned-retry terminal failure wrote a target row "+
+			"into the per-webhook event database",
+	)
+
+	var configs []string
+
+	require.NoError(t, s.WebhookDB.
+		Table("targets").
+		Pluck("config", &configs).Error)
+
+	assert.NotContains(
+		t, strings.Join(configs, " "), hookURL,
+	)
+}
+
 func TestRecoverSingleRetry_UnknownTargetType(
 	t *testing.T,
 ) {
@@ -1125,6 +1201,83 @@ func TestDeliverHTTP_TargetTimeout(t *testing.T) {
 	iAssertResultFailed(t, db, del.ID)
 }
 
+// TestDeliverHTTP_CutsStoredResponseAtMaxBodyLog pins the size
+// this engine stores for an oversized response, because the
+// event log's redaction is written against it: the row holds
+// exactly maxBodyLog bytes and records nothing about how much
+// more the remote sent, so a credential echoed across that
+// boundary reaches the database already severed and no reader
+// of the row can tell the cut happened.
+func TestDeliverHTTP_CutsStoredResponseAtMaxBodyLog(
+	t *testing.T,
+) {
+	t.Parallel()
+
+	// Padded so the cut falls five bytes before the end of the
+	// echoed webhook URL.
+	const (
+		severedTail = 5
+		overshoot   = 100000
+	)
+
+	sent := strings.Repeat(
+		"A",
+		delivery.ExportMaxBodyLog-len(slackWebhookURL)+
+			severedTail,
+	) + slackWebhookURL + strings.Repeat("Z", overshoot)
+
+	s := newISetup(t)
+
+	ts := httptest.NewServer(http.HandlerFunc(
+		func(w http.ResponseWriter, _ *http.Request) {
+			w.WriteHeader(http.StatusBadGateway)
+			_, _ = io.WriteString(w, sent)
+		},
+	))
+	defer ts.Close()
+
+	cfgJSON := iHTTPConfig(ts.URL)
+
+	event := iSeedEvent(
+		t, s.WebhookDB, s.WebhookID, `{"cut":"test"}`,
+	)
+	targetID := uuid.New().String()
+
+	del := iSeedDelivery(
+		t, s.WebhookDB, event.ID, targetID,
+		database.DeliveryStatusPending,
+	)
+
+	bodyStr := event.Body
+	task := iTask(
+		del, event, s.WebhookID, targetID,
+		"cut-target", cfgJSON, 0, 1, &bodyStr,
+	)
+
+	s.Engine.ExportProcessNewTask(context.TODO(), &task)
+
+	results := iResults(t, s.WebhookDB, del.ID)
+	require.Len(t, results, 1)
+
+	stored := results[0].ResponseBody
+
+	assert.Len(
+		t, stored, delivery.ExportMaxBodyLog,
+		"an oversized response is stored at exactly the cap",
+	)
+	assert.Equal(
+		t, sent[:delivery.ExportMaxBodyLog], stored,
+	)
+	assert.NotContains(
+		t, stored, slackWebhookURL,
+		"the echoed URL is severed by the cut",
+	)
+	assert.Contains(
+		t, stored, "T00000000",
+		"the severed prefix still carries the credential",
+	)
+}
+
 // iSeedEventAndDelivery creates event + delivery
 // for standalone tests.
 func iSeedEventAndDelivery(

internal/delivery/export_test.go

@@ -10,6 +10,7 @@ import (
 	"go.uber.org/fx"
 	"gorm.io/gorm"
 	"sneak.berlin/go/webhooker/internal/database"
+	"sneak.berlin/go/webhooker/internal/metrics"
 )
 
 // ErrExportArchiveWriterEvicted exposes the sentinel returned by
@@ -24,6 +25,12 @@ const (
 	ExportRetryChannelSize        = retryChannelSize
 	ExportDefaultFailureThreshold = defaultFailureThreshold
 	ExportDefaultCooldown         = defaultCooldown
+
+	// ExportMaxBodyLog is the cap the engine applies to a
+	// recorded response body. The event log's handling of a cut
+	// response is written against this number, so a test has to
+	// be able to name it.
+	ExportMaxBodyLog = maxBodyLog
 )
 
 // ExportIsBlockedIP exposes isBlockedIP for testing.
@@ -253,6 +260,7 @@ func NewTestEngine(
 		deliveryCh: make(chan Task, deliveryChannelSize),
 		retryCh:    make(chan Task, retryChannelSize),
 		workers:    workers,
+		mtr:        metrics.Default(),
 	}
 	e.initTargets(client)
 
@@ -267,6 +275,7 @@ func NewTestEngineSmallRetry(
 	e := &Engine{
 		log:     log,
 		retryCh: make(chan Task, 1),
+		mtr:     metrics.Default(),
 	}
 	e.initTargets(nil)
 
@@ -289,12 +298,25 @@ func NewTestEngineWithDB(
 		deliveryCh: make(chan Task, deliveryChannelSize),
 		retryCh:    make(chan Task, retryChannelSize),
 		workers:    workers,
+		mtr:        metrics.Default(),
 	}
 	e.initTargets(client)
 
 	return e
 }
 
+// ExportSetMetrics substitutes the engine's metric set, so a test can
+// assert on collectors registered on a private registry instead of
+// the process-wide ones every other test is also moving.
+func (e *Engine) ExportSetMetrics(mtr *metrics.Set) {
+	e.mtr = mtr
+}
+
+// ExportSampleQueueDepths runs one queue depth sample synchronously.
+func (e *Engine) ExportSampleQueueDepths(ctx context.Context) {
+	e.sampleQueueDepths(ctx)
+}
+
 // NewTestCircuitBreaker creates a CircuitBreaker with
 // custom settings for testing.
 func NewTestCircuitBreaker(

internal/delivery/metrics_test.go

@@ -0,0 +1,545 @@
+package delivery_test
+
+import (
+	"context"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/google/uuid"
+	"github.com/prometheus/client_golang/prometheus"
+	dto "github.com/prometheus/client_model/go"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"sneak.berlin/go/webhooker/internal/database"
+	"sneak.berlin/go/webhooker/internal/delivery"
+	"sneak.berlin/go/webhooker/internal/metrics"
+)
+
+// Metric names as exposed on /metrics.
+const (
+	mAttempts  = "webhooker_delivery_attempts_total"
+	mSucceeded = "webhooker_deliveries_succeeded_total"
+	mFailed    = "webhooker_deliveries_failed_total"
+	mRetries   = "webhooker_delivery_retries_total"
+	mDuration  = "webhooker_delivery_duration_seconds"
+	mPending   = "webhooker_deliveries_pending"
+	mRetrying  = "webhooker_deliveries_retrying"
+	mBreakers  = "webhooker_circuit_breakers_open"
+)
+
+const (
+	mTypeHTTP    = "http"
+	mTypeLog     = "log"
+	mTypeUnknown = "unknown"
+)
+
+// mIsolate gives the setup's engine a metric set registered on a
+// private registry. The process-wide collectors are moved by every
+// other delivery test running in parallel, so exact assertions are
+// only possible against a registry this test owns.
+func mIsolate(
+	t *testing.T, s iSetup,
+) *prometheus.Registry {
+	t.Helper()
+
+	reg := prometheus.NewRegistry()
+	s.Engine.ExportSetMetrics(metrics.New(reg))
+
+	return reg
+}
+
+// mFind returns the series of the named metric carrying the given
+// target_type label.
+func mFind(
+	t *testing.T,
+	reg *prometheus.Registry,
+	name, targetType string,
+) *dto.Metric {
+	t.Helper()
+
+	families, err := reg.Gather()
+	require.NoError(t, err)
+
+	for _, fam := range families {
+		if fam.GetName() != name {
+			continue
+		}
+
+		for _, m := range fam.GetMetric() {
+			for _, label := range m.GetLabel() {
+				if label.GetName() == "target_type" &&
+					label.GetValue() == targetType {
+					return m
+				}
+			}
+		}
+	}
+
+	t.Fatalf(
+		"metric %s{target_type=%q} not found",
+		name, targetType,
+	)
+
+	return nil
+}
+
+func mCounter(
+	t *testing.T,
+	reg *prometheus.Registry,
+	name, targetType string,
+) float64 {
+	t.Helper()
+
+	return mFind(t, reg, name, targetType).
+		GetCounter().GetValue()
+}
+
+func mGauge(
+	t *testing.T,
+	reg *prometheus.Registry,
+	name, targetType string,
+) float64 {
+	t.Helper()
+
+	return mFind(t, reg, name, targetType).
+		GetGauge().GetValue()
+}
+
+// mHTTPDurations returns how many samples the delivery duration
+// histogram holds for the http target type, which is the type every
+// test here times.
+func mHTTPDurations(
+	t *testing.T, reg *prometheus.Registry,
+) uint64 {
+	t.Helper()
+
+	return mFind(t, reg, mDuration, mTypeHTTP).
+		GetHistogram().GetSampleCount()
+}
+
+// TestDeliveryMetrics_SuccessAndRetryExhaustion drives one delivery
+// that succeeds and one that fails every attempt until its retries
+// are exhausted, and asserts every delivery counter across both.
+func TestDeliveryMetrics_SuccessAndRetryExhaustion(
+	t *testing.T,
+) {
+	t.Parallel()
+
+	s := newISetup(t)
+	reg := mIsolate(t, s)
+
+	mDeliverOK(t, s)
+
+	assert.InDelta(t, 1.0,
+		mCounter(t, reg, mAttempts, mTypeHTTP), 0)
+	assert.InDelta(t, 1.0,
+		mCounter(t, reg, mSucceeded, mTypeHTTP), 0)
+	assert.InDelta(t, 0.0,
+		mCounter(t, reg, mFailed, mTypeHTTP), 0)
+	assert.InDelta(t, 0.0,
+		mCounter(t, reg, mRetries, mTypeHTTP), 0)
+	assert.Equal(t, uint64(1),
+		mHTTPDurations(t, reg))
+
+	mExhaustRetries(t, s)
+
+	// Two further attempts: the first is retried, the second is
+	// the last one allowed and fails the delivery terminally.
+	assert.InDelta(t, 3.0,
+		mCounter(t, reg, mAttempts, mTypeHTTP), 0)
+	assert.InDelta(t, 1.0,
+		mCounter(t, reg, mSucceeded, mTypeHTTP), 0)
+	assert.InDelta(t, 1.0,
+		mCounter(t, reg, mRetries, mTypeHTTP), 0)
+	assert.InDelta(t, 1.0,
+		mCounter(t, reg, mFailed, mTypeHTTP), 0)
+	assert.Equal(t, uint64(3),
+		mHTTPDurations(t, reg))
+
+	// Two consecutive failures are below the trip threshold.
+	assert.InDelta(t, 0.0,
+		mGauge(t, reg, mBreakers, mTypeHTTP), 0)
+
+	// The label is the target type and nothing finer: two http
+	// targets shared one series, and no other type's moved.
+	assert.InDelta(t, 0.0,
+		mCounter(t, reg, mAttempts, mTypeLog), 0)
+	assert.InDelta(t, 0.0,
+		mCounter(t, reg, mFailed, mTypeLog), 0)
+}
+
+// mDeliverOK delivers one event to a target that answers 200.
+func mDeliverOK(t *testing.T, s iSetup) {
+	t.Helper()
+
+	ts := httptest.NewServer(http.HandlerFunc(
+		func(w http.ResponseWriter, _ *http.Request) {
+			w.WriteHeader(http.StatusOK)
+		},
+	))
+	defer ts.Close()
+
+	event := iSeedEvent(
+		t, s.WebhookDB, s.WebhookID, `{"ok":true}`,
+	)
+	targetID := uuid.New().String()
+
+	d := iSeedDelivery(
+		t, s.WebhookDB, event.ID, targetID,
+		database.DeliveryStatusPending,
+	)
+
+	body := event.Body
+	task := iTask(
+		d, event, s.WebhookID, targetID,
+		"metrics-ok", iHTTPConfig(ts.URL), 3, 1, &body,
+	)
+
+	s.Engine.ExportProcessNewTask(context.TODO(), &task)
+
+	iAssertStatus(t, s.WebhookDB, d.ID,
+		database.DeliveryStatusDelivered,
+	)
+}
+
+// mExhaustRetries delivers to a target that answers 500 with a
+// two-attempt budget, driving both attempts so the delivery ends
+// terminally failed.
+func mExhaustRetries(t *testing.T, s iSetup) {
+	t.Helper()
+
+	ts := httptest.NewServer(http.HandlerFunc(
+		func(w http.ResponseWriter, _ *http.Request) {
+			w.WriteHeader(http.StatusInternalServerError)
+		},
+	))
+	defer ts.Close()
+
+	event := iSeedEvent(
+		t, s.WebhookDB, s.WebhookID, `{"ok":false}`,
+	)
+	targetID := uuid.New().String()
+
+	d := iSeedDelivery(
+		t, s.WebhookDB, event.ID, targetID,
+		database.DeliveryStatusPending,
+	)
+
+	body := event.Body
+	cfg := iHTTPConfig(ts.URL)
+
+	first := iTask(
+		d, event, s.WebhookID, targetID,
+		"metrics-fail", cfg, 2, 1, &body,
+	)
+
+	s.Engine.ExportProcessNewTask(context.TODO(), &first)
+
+	iAssertStatus(t, s.WebhookDB, d.ID,
+		database.DeliveryStatusRetrying,
+	)
+
+	// The engine's own scheduler would re-enqueue this after the
+	// backoff; driving the second attempt directly keeps the test
+	// deterministic and off the wall clock.
+	second := iTask(
+		d, event, s.WebhookID, targetID,
+		"metrics-fail", cfg, 2, 2, &body,
+	)
+
+	s.Engine.ExportProcessRetryTask(
+		context.TODO(), &second,
+	)
+
+	iAssertStatus(t, s.WebhookDB, d.ID,
+		database.DeliveryStatusFailed,
+	)
+}
+
+// TestDeliveryMetrics_CircuitBreakerGauge proves the open-breaker
+// gauge follows a breaker that trips.
+func TestDeliveryMetrics_CircuitBreakerGauge(t *testing.T) {
+	t.Parallel()
+
+	s := newISetup(t)
+	reg := mIsolate(t, s)
+
+	ts := httptest.NewServer(http.HandlerFunc(
+		func(w http.ResponseWriter, _ *http.Request) {
+			w.WriteHeader(http.StatusInternalServerError)
+		},
+	))
+	defer ts.Close()
+
+	event := iSeedEvent(
+		t, s.WebhookDB, s.WebhookID, `{"trip":true}`,
+	)
+	targetID := uuid.New().String()
+
+	d := iSeedDelivery(
+		t, s.WebhookDB, event.ID, targetID,
+		database.DeliveryStatusPending,
+	)
+
+	body := event.Body
+	cfg := iHTTPConfig(ts.URL)
+
+	// A retry budget above the failure threshold, so the breaker
+	// rather than the budget is what stops the delivery.
+	maxRetries := delivery.ExportDefaultFailureThreshold + 5
+
+	first := iTask(
+		d, event, s.WebhookID, targetID,
+		"metrics-trip", cfg, maxRetries, 1, &body,
+	)
+
+	s.Engine.ExportProcessNewTask(context.TODO(), &first)
+
+	assert.InDelta(t, 0.0,
+		mGauge(t, reg, mBreakers, mTypeHTTP), 0)
+
+	for attempt := 2; attempt <= delivery.
+		ExportDefaultFailureThreshold; attempt++ {
+		task := iTask(
+			d, event, s.WebhookID, targetID,
+			"metrics-trip", cfg, maxRetries, attempt, &body,
+		)
+
+		s.Engine.ExportProcessRetryTask(
+			context.TODO(), &task,
+		)
+	}
+
+	assert.InDelta(t, 1.0,
+		mGauge(t, reg, mBreakers, mTypeHTTP), 0)
+}
+
+// TestDeliveryMetrics_BreakerBlockedIsNotAnAttempt proves a delivery
+// an open circuit breaker refuses is neither counted as an attempt
+// nor observed in the duration histogram.
+//
+// It sends nothing and records no result row, so counting it would
+// climb the attempts counter with no traffic behind it and pull the
+// duration quantiles down with near-zero samples for as long as the
+// breaker stayed open — the metric moving the wrong way during the
+// outage it exists to reveal.
+func TestDeliveryMetrics_BreakerBlockedIsNotAnAttempt(
+	t *testing.T,
+) {
+	t.Parallel()
+
+	s := newISetup(t)
+	reg := mIsolate(t, s)
+
+	ts := httptest.NewServer(http.HandlerFunc(
+		func(w http.ResponseWriter, _ *http.Request) {
+			w.WriteHeader(http.StatusInternalServerError)
+		},
+	))
+	defer ts.Close()
+
+	event := iSeedEvent(
+		t, s.WebhookDB, s.WebhookID, `{"blocked":true}`,
+	)
+	targetID := uuid.New().String()
+
+	d := iSeedDelivery(
+		t, s.WebhookDB, event.ID, targetID,
+		database.DeliveryStatusPending,
+	)
+
+	body := event.Body
+	cfg := iHTTPConfig(ts.URL)
+	maxRetries := delivery.ExportDefaultFailureThreshold + 5
+
+	first := iTask(
+		d, event, s.WebhookID, targetID,
+		"metrics-blocked", cfg, maxRetries, 1, &body,
+	)
+
+	s.Engine.ExportProcessNewTask(context.TODO(), &first)
+
+	for attempt := 2; attempt <= delivery.
+		ExportDefaultFailureThreshold; attempt++ {
+		task := iTask(
+			d, event, s.WebhookID, targetID,
+			"metrics-blocked", cfg, maxRetries, attempt, &body,
+		)
+
+		s.Engine.ExportProcessRetryTask(context.TODO(), &task)
+	}
+
+	require.InDelta(t, 1.0,
+		mGauge(t, reg, mBreakers, mTypeHTTP), 0,
+		"breaker should be open before the blocked attempt")
+
+	threshold := float64(
+		delivery.ExportDefaultFailureThreshold,
+	)
+
+	assert.InDelta(t, threshold,
+		mCounter(t, reg, mAttempts, mTypeHTTP), 0)
+	assert.Equal(t, uint64(threshold),
+		mHTTPDurations(t, reg))
+
+	retriesBefore := mCounter(t, reg, mRetries, mTypeHTTP)
+
+	blocked := iTask(
+		d, event, s.WebhookID, targetID,
+		"metrics-blocked", cfg, maxRetries,
+		delivery.ExportDefaultFailureThreshold+1, &body,
+	)
+
+	s.Engine.ExportProcessRetryTask(context.TODO(), &blocked)
+
+	// The breaker refused it: rescheduled, so the retry counter
+	// moved, but nothing was attempted or timed.
+	assert.InDelta(t, retriesBefore+1,
+		mCounter(t, reg, mRetries, mTypeHTTP), 0)
+	assert.InDelta(t, threshold,
+		mCounter(t, reg, mAttempts, mTypeHTTP), 0)
+	assert.Equal(t, uint64(threshold),
+		mHTTPDurations(t, reg))
+}
+
+// TestDeliveryMetrics_OrphanedRetryFailureLabelled proves the
+// terminal failure of a delivery whose target no longer retries is
+// counted against the target's real type, not against unknown. The
+// type is threaded in as an argument because populating d.Target on
+// that path would write the target row into the per-webhook database
+// (https://git.eeqj.de/sneak/webhooker/issues/206).
+func TestDeliveryMetrics_OrphanedRetryFailureLabelled(
+	t *testing.T,
+) {
+	t.Parallel()
+
+	s := newISetup(t)
+	reg := mIsolate(t, s)
+
+	iCreateWebhook(
+		t, s.MainDB, s.WebhookID, "orphaned-label",
+	)
+
+	deliveryID := iSeedRetryingWithType(
+		t, s, database.TargetTypeLog,
+	)
+
+	s.Engine.ExportSweepWebhookRetries(
+		context.Background(), s.WebhookID,
+	)
+
+	iAssertStatus(t, s.WebhookDB, deliveryID,
+		database.DeliveryStatusFailed,
+	)
+
+	assert.InDelta(t, 1.0,
+		mCounter(t, reg, mFailed, mTypeLog), 0)
+}
+
+// TestDeliveryMetrics_QueueDepthGauges proves the sampler publishes
+// the queued deliveries it finds in the per-webhook databases, and
+// that a drained queue reads zero rather than keeping its last
+// value.
+func TestDeliveryMetrics_QueueDepthGauges(t *testing.T) {
+	t.Parallel()
+
+	s := newISetup(t)
+	reg := mIsolate(t, s)
+
+	iCreateWebhook(
+		t, s.MainDB, s.WebhookID, "queue-depth",
+	)
+
+	targetID := uuid.New().String()
+
+	iCreateTarget(t, s.MainDB, targetID, s.WebhookID,
+		"queue-depth-target", database.TargetTypeHTTP,
+		iHTTPConfig("https://example.com/hook"), 3,
+	)
+
+	event := iSeedEvent(
+		t, s.WebhookDB, s.WebhookID, `{"queued":true}`,
+	)
+
+	pending := iSeedDelivery(
+		t, s.WebhookDB, event.ID, targetID,
+		database.DeliveryStatusPending,
+	)
+
+	iSeedDelivery(
+		t, s.WebhookDB, event.ID, targetID,
+		database.DeliveryStatusPending,
+	)
+
+	retrying := iSeedDelivery(
+		t, s.WebhookDB, event.ID, targetID,
+		database.DeliveryStatusRetrying,
+	)
+
+	s.Engine.ExportSampleQueueDepths(context.Background())
+
+	assert.InDelta(t, 2.0,
+		mGauge(t, reg, mPending, mTypeHTTP), 0)
+	assert.InDelta(t, 1.0,
+		mGauge(t, reg, mRetrying, mTypeHTTP), 0)
+	assert.InDelta(t, 0.0,
+		mGauge(t, reg, mPending, mTypeLog), 0)
+
+	require.NoError(t, s.WebhookDB.
+		Model(&database.Delivery{}).
+		Where("id IN ?", []string{pending.ID, retrying.ID}).
+		Update(
+			"status", database.DeliveryStatusDelivered,
+		).Error)
+
+	s.Engine.ExportSampleQueueDepths(context.Background())
+
+	assert.InDelta(t, 1.0,
+		mGauge(t, reg, mPending, mTypeHTTP), 0)
+	assert.InDelta(t, 0.0,
+		mGauge(t, reg, mRetrying, mTypeHTTP), 0)
+}
+
+// TestDeliveryMetrics_QueueDepthDeletedTarget proves a backlog queued
+// against a target that has since been deleted stays visible, in the
+// unknown series, instead of being dropped. That backlog is the one
+// nobody is watching, so losing it would defeat the queue-depth
+// alerting this metric exists for.
+func TestDeliveryMetrics_QueueDepthDeletedTarget(t *testing.T) {
+	t.Parallel()
+
+	s := newISetup(t)
+	reg := mIsolate(t, s)
+
+	iCreateWebhook(
+		t, s.MainDB, s.WebhookID, "deleted-target",
+	)
+
+	// No target row is created: this is a delivery whose target was
+	// deleted out from under it.
+	targetID := uuid.New().String()
+
+	event := iSeedEvent(
+		t, s.WebhookDB, s.WebhookID, `{"orphan":true}`,
+	)
+
+	iSeedDelivery(
+		t, s.WebhookDB, event.ID, targetID,
+		database.DeliveryStatusPending,
+	)
+
+	iSeedDelivery(
+		t, s.WebhookDB, event.ID, targetID,
+		database.DeliveryStatusRetrying,
+	)
+
+	s.Engine.ExportSampleQueueDepths(context.Background())
+
+	assert.InDelta(t, 1.0,
+		mGauge(t, reg, mPending, mTypeUnknown), 0)
+	assert.InDelta(t, 1.0,
+		mGauge(t, reg, mRetrying, mTypeUnknown), 0)
+	assert.InDelta(t, 0.0,
+		mGauge(t, reg, mPending, mTypeHTTP), 0)
+}

internal/delivery/queue_depth.go

@@ -0,0 +1,187 @@
+package delivery
+
+import (
+	"context"
+	"fmt"
+	"time"
+
+	"sneak.berlin/go/webhooker/internal/database"
+)
+
+// queueDepthSampleInterval is how often the pending and retrying
+// queue depths are counted and published as gauges.
+const queueDepthSampleInterval = 30 * time.Second
+
+// queueDepthSampler publishes the pending and retrying queue depths
+// on a timer for as long as the engine runs.
+//
+// The depths are counted out of the databases rather than tracked as
+// deltas alongside the status transitions. A delta counter would have
+// to be seeded correctly at startup from rows written by a previous
+// process, and would drift permanently on any transition that failed
+// to persist. Counting is the measurement that cannot go wrong, and
+// it is the same whole-database walk the retry sweep already makes.
+func (e *Engine) queueDepthSampler(ctx context.Context) {
+	defer e.wg.Done()
+
+	ticker := time.NewTicker(queueDepthSampleInterval)
+	defer ticker.Stop()
+
+	e.sampleQueueDepths(ctx)
+
+	for {
+		select {
+		case <-ctx.Done():
+			return
+		case <-ticker.C:
+			e.sampleQueueDepths(ctx)
+		}
+	}
+}
+
+// sampleQueueDepths counts every queued delivery across all
+// per-webhook databases and publishes the result.
+func (e *Engine) sampleQueueDepths(ctx context.Context) {
+	if e.database == nil || e.dbManager == nil {
+		return
+	}
+
+	types, err := e.targetTypesByID()
+	if err != nil {
+		e.log.Error(
+			"queue depth sample: failed to load target types",
+			"error", err,
+		)
+
+		return
+	}
+
+	var webhookIDs []string
+
+	err = e.database.DB().
+		Model(&database.Webhook{}).
+		Pluck("id", &webhookIDs).Error
+	if err != nil {
+		e.log.Error(
+			"queue depth sample: failed to query webhook IDs",
+			"error", err,
+		)
+
+		return
+	}
+
+	pending := make(map[database.TargetType]int)
+	retrying := make(map[database.TargetType]int)
+
+	for _, webhookID := range webhookIDs {
+		select {
+		case <-ctx.Done():
+			return
+		default:
+		}
+
+		if !e.dbManager.DBExists(webhookID) {
+			continue
+		}
+
+		e.sampleWebhookQueueDepths(
+			webhookID, types, pending, retrying,
+		)
+	}
+
+	e.mtr.SetQueueDepths(pending, retrying)
+}
+
+// targetTypesByID maps every configured target id to its type. The
+// deliveries live in the per-webhook databases but carry only a
+// target id, so the type label has to come from the main database.
+func (e *Engine) targetTypesByID() (
+	map[string]database.TargetType, error,
+) {
+	var rows []struct {
+		ID   string
+		Type database.TargetType
+	}
+
+	err := e.database.DB().
+		Model(&database.Target{}).
+		Select("id", "type").
+		Scan(&rows).Error
+	if err != nil {
+		return nil, fmt.Errorf("loading targets: %w", err)
+	}
+
+	types := make(map[string]database.TargetType, len(rows))
+
+	for _, row := range rows {
+		types[row.ID] = row.Type
+	}
+
+	return types, nil
+}
+
+// sampleWebhookQueueDepths adds one webhook's queued deliveries into
+// the running totals.
+//
+// A delivery whose target has since been deleted is not in the type
+// map and so counts under the empty target type. Set.SetQueueDepths
+// folds that into the unknown series rather than dropping it: a
+// backlog stuck behind a deleted target is a backlog that still needs
+// to be alertable.
+func (e *Engine) sampleWebhookQueueDepths(
+	webhookID string,
+	types map[string]database.TargetType,
+	pending, retrying map[database.TargetType]int,
+) {
+	webhookDB, err := e.dbManager.GetDB(webhookID)
+	if err != nil {
+		e.log.Error(
+			"queue depth sample: failed to get webhook database",
+			"webhook_id", webhookID,
+			"error", err,
+		)
+
+		return
+	}
+
+	var rows []struct {
+		TargetID string
+		Status   database.DeliveryStatus
+		Depth    int
+	}
+
+	err = webhookDB.
+		Model(&database.Delivery{}).
+		Select("target_id", "status", "count(*) as depth").
+		Where("status IN ?", []database.DeliveryStatus{
+			database.DeliveryStatusPending,
+			database.DeliveryStatusRetrying,
+		}).
+		Group("target_id, status").
+		Scan(&rows).Error
+	if err != nil {
+		e.log.Error(
+			"queue depth sample: "+
+				"failed to count queued deliveries",
+			"webhook_id", webhookID,
+			"error", err,
+		)
+
+		return
+	}
+
+	for _, row := range rows {
+		targetType := types[row.TargetID]
+
+		switch row.Status {
+		case database.DeliveryStatusPending:
+			pending[targetType] += row.Depth
+		case database.DeliveryStatusRetrying:
+			retrying[targetType] += row.Depth
+		case database.DeliveryStatusDelivered,
+			database.DeliveryStatusFailed:
+			// Excluded by the query above: a delivery that has
+			// reached a terminal state is not queued.
+		}
+	}
+}

internal/delivery/target.go

@@ -27,6 +27,12 @@ type Scheduler interface {
 // own circuit breaker, and reschedules via the injected
 // Scheduler. Fire-and-forget targets simply record a single
 // attempt.
+//
+// An implementation reports each attempt it actually dispatches to
+// Engine.observeAttempt, alongside the DeliveryResult it records for
+// it. Deliver is also entered for attempts that never happen — an
+// open circuit breaker refuses one — so the count cannot be taken
+// from around this call.
 type Target interface {
 	Deliver(
 		ctx context.Context,
@@ -74,6 +80,12 @@ type attemptResult struct {
 	errMsg     string
 }
 
+// elapsed returns how long the attempt took. The field is stored in
+// milliseconds because that is what DeliveryResult persists.
+func (r attemptResult) elapsed() time.Duration {
+	return time.Duration(r.duration) * time.Millisecond
+}
+
 // initTargets builds the target registry, wiring each target
 // to the engine's persistence helpers and giving the HTTP and
 // Slack targets the shared SSRF-safe client. It is called by

internal/delivery/target_config_edit.go

@@ -0,0 +1,119 @@
+package delivery
+
+import (
+	"encoding/json"
+	"errors"
+	"fmt"
+
+	"sneak.berlin/go/webhooker/internal/database"
+)
+
+// errUnknownTargetTypeForEdit is returned when a stored target has a
+// type the edit form has no field set for.
+var errUnknownTargetTypeForEdit = errors.New(
+	"unknown target type",
+)
+
+// TargetConfigForm is the UNMASKED projection of a target's stored
+// configuration, for pre-filling the target edit form.
+//
+// It is the deliberate exception to the rule TargetView enforces
+// everywhere else: TargetView exists so that no template can render
+// a target's stored blob, because a destination URL's path segments
+// and a header value are both routinely the credential. An operator
+// cannot correct a value they cannot see, so the edit form — and
+// only the edit form — is shown the full value.
+//
+// Everything that keeps that exception narrow lives at the call
+// site: the route is behind RequireAuth and the webhook's ownership
+// check, and its group sets NoCache so the rendered secret is not
+// written to a shared cache. Do not reach for this type from any
+// other page.
+type TargetConfigForm struct {
+	// URL is the destination for an HTTP target and the webhook
+	// URL for a Slack target.
+	URL string
+	// Headers is the HTTP target's configured headers in the
+	// textarea representation, one "Name: value" per line.
+	Headers string
+	// Timeout is the HTTP target's per-request timeout in seconds,
+	// empty when unset.
+	Timeout string
+	// Expiry is the database (archive) target's row expiry.
+	Expiry string
+}
+
+// NewTargetConfigForm parses a target's stored configuration into
+// the edit form's fields.
+//
+// A configuration that does not parse is an error rather than a
+// zero-valued form that silently looks like a target with no
+// settings. The caller shows the operator that the stored value
+// could not be read, so that saving the form is understood as
+// replacing it rather than preserving it.
+func NewTargetConfigForm(
+	t *database.Target,
+) (TargetConfigForm, error) {
+	switch t.Type {
+	case database.TargetTypeHTTP:
+		cfg, err := parseHTTPConfig(t.Config)
+		if err != nil {
+			return TargetConfigForm{}, err
+		}
+
+		return TargetConfigForm{
+			URL:     cfg.URL,
+			Headers: FormatTargetHeaders(cfg.Headers),
+			Timeout: FormatTargetTimeout(cfg.Timeout),
+		}, nil
+	case database.TargetTypeSlack:
+		cfg, err := parseSlackConfig(t.Config)
+		if err != nil {
+			return TargetConfigForm{}, err
+		}
+
+		return TargetConfigForm{URL: cfg.WebhookURL}, nil
+	case database.TargetTypeDatabase:
+		return databaseConfigForm(t.Config)
+	case database.TargetTypeLog:
+		// The log target takes no configuration.
+		return TargetConfigForm{}, nil
+	default:
+		return TargetConfigForm{}, fmt.Errorf(
+			"%w: %q", errUnknownTargetTypeForEdit, t.Type,
+		)
+	}
+}
+
+// databaseConfigForm parses an archive target's optional expiry.
+// An absent or empty configuration is the keep-forever default and
+// yields an empty field, so re-saving the form unchanged stores the
+// same empty configuration it started with. An expiry that is set
+// but not a valid duration is an error, not a blank field.
+func databaseConfigForm(
+	configJSON string,
+) (TargetConfigForm, error) {
+	if configJSON == "" {
+		return TargetConfigForm{}, nil
+	}
+
+	var cfg databaseTargetConfig
+
+	err := json.Unmarshal([]byte(configJSON), &cfg)
+	if err != nil {
+		return TargetConfigForm{}, fmt.Errorf(
+			"parsing config JSON: %w", err,
+		)
+	}
+
+	if cfg.Expiry == "" || cfg.Expiry == archiveExpiryNever {
+		return TargetConfigForm{}, nil
+	}
+
+	err = ValidateArchiveExpiry(cfg.Expiry)
+	if err != nil {
+		return TargetConfigForm{}, err
+	}
+
+	return TargetConfigForm{Expiry: cfg.Expiry}, nil
+}

internal/delivery/target_database.go

@@ -42,7 +42,14 @@ func (t *databaseTarget) Deliver(
 	_ *Task,
 	_ Scheduler,
 ) {
+	start := time.Now()
+
 	err := t.archive(d)
+
+	elapsed := time.Since(start)
+
+	t.eng.observeAttempt(d.Target.Type, elapsed)
+
 	if err != nil {
 		t.eng.log.Error(
 			"failed to archive event to database target",
@@ -53,22 +60,25 @@ func (t *databaseTarget) Deliver(
 
 		t.eng.recordResult(
 			webhookDB, d, 1, false, 0, "",
-			err.Error(), 0,
+			err.Error(), elapsed.Milliseconds(),
 		)
 
 		t.eng.updateDeliveryStatus(
-			webhookDB, d, database.DeliveryStatusFailed,
+			webhookDB, d, d.Target.Type,
+			database.DeliveryStatusFailed,
 		)
 
 		return
 	}
 
 	t.eng.recordResult(
-		webhookDB, d, 1, true, 0, "", "", 0,
+		webhookDB, d, 1, true, 0, "", "",
+		elapsed.Milliseconds(),
 	)
 
 	t.eng.updateDeliveryStatus(
-		webhookDB, d, database.DeliveryStatusDelivered,
+		webhookDB, d, d.Target.Type,
+		database.DeliveryStatusDelivered,
 	)
 }
 

internal/delivery/target_headers.go

@@ -0,0 +1,256 @@
+package delivery
+
+import (
+	"errors"
+	"fmt"
+	"net/http"
+	"slices"
+	"strconv"
+	"strings"
+)
+
+// MaxTargetTimeoutSeconds bounds a per-target request timeout.
+// A delivery attempt holds a worker for its whole duration, so an
+// unbounded timeout lets one misconfigured target stall the queue
+// indefinitely. Five minutes is far beyond any healthy webhook
+// receiver and still finite.
+const MaxTargetTimeoutSeconds = 300
+
+// Errors returned when a target's header or timeout form input
+// cannot be turned into a configuration.
+//
+// None of these ever quotes a header VALUE. A target header value
+// is routinely an authorization token, and these messages are shown
+// to the user in an error page body.
+var (
+	errHeaderLineMalformed = errors.New(
+		`each header line must be "Name: value"`,
+	)
+	errHeaderNameInvalid = errors.New(
+		"header name must be a valid HTTP token",
+	)
+	errHeaderValueInvalid = errors.New(
+		"header value must not contain control characters",
+	)
+	errHeaderDuplicate = errors.New(
+		"header given more than once",
+	)
+	errHeaderReserved = errors.New(
+		"header is set by the delivery engine and cannot be " +
+			"overridden",
+	)
+	errTimeoutInvalid = errors.New(
+		"timeout must be a whole number of seconds",
+	)
+	errTimeoutOutOfRange = errors.New(
+		"timeout is out of range",
+	)
+)
+
+// isReservedTargetHeader reports whether name (canonicalised) is a
+// header a target configuration may not set, because the delivery
+// path or net/http itself writes it regardless.
+//
+// These are rejected rather than accepted-and-ignored. Storing a
+// header that provably never reaches the wire tells the operator
+// their configuration took effect when it did not, which is the
+// same failure mode as silently substituting a default for an
+// invalid value.
+func isReservedTargetHeader(name string) bool {
+	switch name {
+	case "Host", "Content-Length", "Transfer-Encoding", "Connection":
+		return true
+	case "User-Agent":
+		// applyRequestHeaders sets the User-Agent after it applies
+		// the configured headers, so a configured one would always
+		// be overwritten.
+		return true
+	default:
+		return false
+	}
+}
+
+// ParseTargetHeaders turns the target form's headers field — one
+// "Name: value" pair per line, blank lines ignored — into the map
+// stored in HTTPTargetConfig.Headers. Names are canonicalised, so a
+// name repeated in a different case is still a duplicate rather than
+// one pair silently overwriting the other.
+//
+// An input with no pairs yields an empty map, which omitempty drops
+// from the stored config: a target configured with no headers keeps
+// the same config JSON it had before this field existed.
+func ParseTargetHeaders(raw string) (map[string]string, error) {
+	headers := make(map[string]string)
+
+	for i, line := range strings.Split(raw, "\n") {
+		lineNum := i + 1
+
+		line = strings.TrimSpace(line)
+		if line == "" {
+			continue
+		}
+
+		name, value, err := parseHeaderLine(line)
+		if err != nil {
+			return nil, fmt.Errorf("line %d: %w", lineNum, err)
+		}
+
+		if _, dup := headers[name]; dup {
+			return nil, fmt.Errorf(
+				"line %d: %w: %q", lineNum,
+				errHeaderDuplicate, name,
+			)
+		}
+
+		headers[name] = value
+	}
+
+	return headers, nil
+}
+
+// parseHeaderLine splits and validates one "Name: value" line,
+// returning the canonicalised name and the trimmed value.
+func parseHeaderLine(line string) (string, string, error) {
+	rawName, value, found := strings.Cut(line, ":")
+	if !found {
+		return "", "", errHeaderLineMalformed
+	}
+
+	rawName = strings.TrimSpace(rawName)
+	if !validHeaderName(rawName) {
+		return "", "", fmt.Errorf(
+			"%w: %q", errHeaderNameInvalid, rawName,
+		)
+	}
+
+	name := http.CanonicalHeaderKey(rawName)
+	if isReservedTargetHeader(name) {
+		return "", "", fmt.Errorf(
+			"%w: %q", errHeaderReserved, name,
+		)
+	}
+
+	value = strings.TrimSpace(value)
+	if !validHeaderValue(value) {
+		return "", "", fmt.Errorf(
+			"%w: %q", errHeaderValueInvalid, name,
+		)
+	}
+
+	return name, value, nil
+}
+
+// validHeaderName reports whether name is a non-empty RFC 9110
+// field name. Rejecting anything else here is what keeps a value
+// containing CR or LF from being smuggled in as part of a name and
+// injecting a second header into the outbound request.
+func validHeaderName(name string) bool {
+	if name == "" {
+		return false
+	}
+
+	for i := range len(name) {
+		if !isTokenByte(name[i]) {
+			return false
+		}
+	}
+
+	return true
+}
+
+// isTokenByte reports whether c is a "tchar" per RFC 9110 5.6.2.
+func isTokenByte(c byte) bool {
+	switch {
+	case c >= 'a' && c <= 'z',
+		c >= 'A' && c <= 'Z',
+		c >= '0' && c <= '9':
+		return true
+	}
+
+	return strings.IndexByte("!#$%&'*+-.^_`|~", c) >= 0
+}
+
+// validHeaderValue reports whether value is a legal field value:
+// no control characters, which is the other half of the header
+// injection guard. An empty value is legal.
+func validHeaderValue(value string) bool {
+	for i := range len(value) {
+		c := value[i]
+		if c < 0x20 || c == 0x7f {
+			return false
+		}
+	}
+
+	return true
+}
+
+// FormatTargetHeaders renders a stored header map back into the
+// form's textarea representation, one "Name: value" per line.
+//
+// Names are sorted so that loading the edit form twice without
+// saving produces identical text; Go map iteration order would
+// otherwise reshuffle the field on every render.
+func FormatTargetHeaders(headers map[string]string) string {
+	if len(headers) == 0 {
+		return ""
+	}
+
+	names := make([]string, 0, len(headers))
+	for name := range headers {
+		names = append(names, name)
+	}
+
+	slices.Sort(names)
+
+	var b strings.Builder
+
+	for _, name := range names {
+		b.WriteString(name)
+		b.WriteString(": ")
+		b.WriteString(headers[name])
+		b.WriteString("\n")
+	}
+
+	return b.String()
+}
+
+// ParseTargetTimeout interprets the target form's timeout field as
+// a whole number of seconds. An empty field means "unset" and yields
+// 0, which omitempty drops from the stored config and which the
+// delivery path reads as "use the shared client's timeout".
+//
+// Anything else that is not a whole number in range is an error, not
+// a silently substituted default: a target whose timeout was typed
+// wrong must say so at the form rather than deliver on a timeout its
+// operator did not choose.
+func ParseTargetTimeout(raw string) (int, error) {
+	raw = strings.TrimSpace(raw)
+	if raw == "" {
+		return 0, nil
+	}
+
+	v, err := strconv.Atoi(raw)
+	if err != nil || v < 0 {
+		return 0, errTimeoutInvalid
+	}
+
+	if v > MaxTargetTimeoutSeconds {
+		return 0, fmt.Errorf(
+			"%w: at most %d seconds",
+			errTimeoutOutOfRange, MaxTargetTimeoutSeconds,
+		)
+	}
+
+	return v, nil
+}
+
+// FormatTargetTimeout renders a stored timeout for the form field.
+// An unset timeout renders as an empty field rather than "0", so the
+// placeholder can describe the default the target actually uses.
+func FormatTargetTimeout(timeout int) string {
+	if timeout <= 0 {
+		return ""
+	}
+
+	return strconv.Itoa(timeout)
+}

internal/delivery/target_headers_test.go

@@ -0,0 +1,273 @@
+package delivery_test
+
+import (
+	"encoding/json"
+	"strconv"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"sneak.berlin/go/webhooker/internal/database"
+	"sneak.berlin/go/webhooker/internal/delivery"
+)
+
+// Literals these tests repeat, named so that the header name and the
+// keep-forever archive config each have one definition.
+const (
+	headerAuthorization = "Authorization"
+	bearerValue         = "Bearer abc"
+	archiveConfigNever  = "{\"expiry\":\"never\"}"
+)
+
+func TestParseTargetHeaders_AcceptsPairs(t *testing.T) {
+	t.Parallel()
+
+	got, err := delivery.ParseTargetHeaders(
+		"  Authorization: Bearer abc \n\n" +
+			"x-tenant:acme\r\n" +
+			"X-Empty:\n",
+	)
+	require.NoError(t, err)
+
+	assert.Equal(
+		t,
+		map[string]string{
+			headerAuthorization: bearerValue,
+			"X-Tenant":          "acme",
+			"X-Empty":           "",
+		},
+		got,
+	)
+}
+
+// A configuration with no headers must stay indistinguishable from
+// one written before the field existed, so omitempty drops the key.
+func TestParseTargetHeaders_EmptyInputYieldsNoHeaders(t *testing.T) {
+	t.Parallel()
+
+	got, err := delivery.ParseTargetHeaders("\n  \n")
+	require.NoError(t, err)
+	assert.Empty(t, got)
+
+	encoded, err := json.Marshal(delivery.HTTPTargetConfig{
+		URL:     "https://example.com/h",
+		Headers: got,
+	})
+	require.NoError(t, err)
+	assert.JSONEq(
+		t, `{"url":"https://example.com/h"}`, string(encoded),
+	)
+}
+
+func TestParseTargetHeaders_Rejects(t *testing.T) {
+	t.Parallel()
+
+	cases := map[string]string{
+		"no colon":           "Authorization Bearer abc",
+		"empty name":         ": value",
+		"space in name":      "X Bad: value",
+		"reserved host":      "Host: evil.example",
+		"reserved ua":        "User-Agent: curl/8",
+		"reserved length":    "Content-Length: 0",
+		"duplicate any case": "X-A: 1\nx-a: 2",
+	}
+
+	for name, input := range cases {
+		t.Run(name, func(t *testing.T) {
+			t.Parallel()
+
+			_, err := delivery.ParseTargetHeaders(input)
+			require.Error(t, err)
+		})
+	}
+}
+
+// A header value is routinely a bearer token and these errors are
+// rendered into a 400 body, so no message may quote one.
+func TestParseTargetHeaders_ErrorsNeverQuoteAValue(t *testing.T) {
+	t.Parallel()
+
+	const secret = "QQNEVERINAMESSAGEQQ"
+
+	_, err := delivery.ParseTargetHeaders(
+		"X-A: " + secret + "\nx-a: " + secret,
+	)
+	require.Error(t, err)
+	assert.NotContains(t, err.Error(), secret)
+
+	_, err = delivery.ParseTargetHeaders(
+		"X Bad Name: " + secret,
+	)
+	require.Error(t, err)
+	assert.NotContains(t, err.Error(), secret)
+}
+
+// Loading the edit form twice without saving must not reshuffle
+// the textarea, which Go's map iteration order would otherwise do.
+func TestFormatTargetHeaders_IsSorted(t *testing.T) {
+	t.Parallel()
+
+	got := delivery.FormatTargetHeaders(map[string]string{
+		"X-Zed":             "z",
+		headerAuthorization: bearerValue,
+		"X-Alpha":           "a",
+	})
+
+	assert.Equal(
+		t,
+		"Authorization: Bearer abc\nX-Alpha: a\nX-Zed: z\n",
+		got,
+	)
+	assert.Empty(t, delivery.FormatTargetHeaders(nil))
+}
+
+func TestFormatTargetHeaders_RoundTripsThroughParse(t *testing.T) {
+	t.Parallel()
+
+	want := map[string]string{
+		headerAuthorization: bearerValue,
+		"X-Tenant":          "acme",
+	}
+
+	got, err := delivery.ParseTargetHeaders(
+		delivery.FormatTargetHeaders(want),
+	)
+	require.NoError(t, err)
+	assert.Equal(t, want, got)
+}
+
+func TestParseTargetTimeout(t *testing.T) {
+	t.Parallel()
+
+	got, err := delivery.ParseTargetTimeout("  30 ")
+	require.NoError(t, err)
+	assert.Equal(t, 30, got)
+
+	got, err = delivery.ParseTargetTimeout("")
+	require.NoError(t, err)
+	assert.Zero(t, got)
+
+	for _, bad := range []string{"soon", "-1", "1e3", "100000"} {
+		_, err = delivery.ParseTargetTimeout(bad)
+		require.Error(t, err, bad)
+	}
+}
+
+func TestFormatTargetTimeout(t *testing.T) {
+	t.Parallel()
+
+	assert.Equal(t, "30", delivery.FormatTargetTimeout(30))
+	assert.Empty(t, delivery.FormatTargetTimeout(0))
+	assert.Empty(t, delivery.FormatTargetTimeout(-1))
+}
+
+func TestNewTargetConfigForm(t *testing.T) {
+	t.Parallel()
+
+	form, err := delivery.NewTargetConfigForm(&database.Target{
+		Type: database.TargetTypeHTTP,
+		Config: `{"url":"https://example.com/h",` +
+			`"headers":{"Authorization":"Bearer abc"},` +
+			`"timeout":9}`,
+	})
+	require.NoError(t, err)
+	assert.Equal(t, "https://example.com/h", form.URL)
+	assert.Equal(t, "Authorization: Bearer abc\n", form.Headers)
+	assert.Equal(t, "9", form.Timeout)
+
+	form, err = delivery.NewTargetConfigForm(&database.Target{
+		Type:   database.TargetTypeSlack,
+		Config: `{"webhookUrl":"https://hooks.example/s"}`,
+	})
+	require.NoError(t, err)
+	assert.Equal(t, "https://hooks.example/s", form.URL)
+
+	form, err = delivery.NewTargetConfigForm(&database.Target{
+		Type:   database.TargetTypeDatabase,
+		Config: `{"expiry":"720h"}`,
+	})
+	require.NoError(t, err)
+	assert.Equal(t, "720h", form.Expiry)
+
+	form, err = delivery.NewTargetConfigForm(&database.Target{
+		Type: database.TargetTypeLog,
+	})
+	require.NoError(t, err)
+	assert.Empty(t, form.URL)
+}
+
+// A keep-forever archive target must pre-fill as an empty field, so
+// saving the form back unchanged stores the same empty config.
+func TestNewTargetConfigForm_DatabaseNeverIsBlank(t *testing.T) {
+	t.Parallel()
+
+	for _, cfg := range []string{"", `{}`, archiveConfigNever} {
+		form, err := delivery.NewTargetConfigForm(
+			&database.Target{
+				Type:   database.TargetTypeDatabase,
+				Config: cfg,
+			},
+		)
+		require.NoError(t, err, cfg)
+		assert.Empty(t, form.Expiry, cfg)
+	}
+}
+
+// An unreadable stored config is an error rather than a blank form
+// that looks like a target with no settings, so the caller can tell
+// the operator that saving replaces the stored value.
+func TestNewTargetConfigForm_UnreadableConfigErrors(t *testing.T) {
+	t.Parallel()
+
+	cases := []*database.Target{
+		{Type: database.TargetTypeHTTP, Config: "not json"},
+		{Type: database.TargetTypeHTTP, Config: `{}`},
+		{Type: database.TargetTypeSlack, Config: ""},
+		{
+			Type:   database.TargetTypeDatabase,
+			Config: `{"expiry":"soon"}`,
+		},
+		{Type: database.TargetType("nope")},
+	}
+
+	for _, target := range cases {
+		_, err := delivery.NewTargetConfigForm(target)
+		require.Error(t, err, target.Type)
+	}
+}
+
+// The ceiling exists so one misconfigured target cannot hold a
+// delivery worker indefinitely, and it is inclusive.
+func TestParseTargetTimeout_CeilingIsInclusive(t *testing.T) {
+	t.Parallel()
+
+	assert.Positive(t, delivery.MaxTargetTimeoutSeconds)
+
+	got, err := delivery.ParseTargetTimeout(
+		strconv.Itoa(delivery.MaxTargetTimeoutSeconds),
+	)
+	require.NoError(t, err)
+	assert.Equal(t, delivery.MaxTargetTimeoutSeconds, got)
+
+	_, err = delivery.ParseTargetTimeout(
+		strconv.Itoa(delivery.MaxTargetTimeoutSeconds + 1),
+	)
+	require.Error(t, err)
+}
+
+// Control characters in a value are how a second header would be
+// smuggled into the outbound request.
+func TestParseTargetHeaders_RejectsControlCharactersInValues(
+	t *testing.T,
+) {
+	t.Parallel()
+
+	for _, bad := range []string{
+		"X-A: one\x01two",
+		"X-A: one\ttwo",
+		"X-A: one\x7ftwo",
+	} {
+		_, err := delivery.ParseTargetHeaders(bad)
+		require.Error(t, err, bad)
+	}
+}

internal/delivery/target_http.go

@@ -74,6 +74,8 @@ func (c *httpCore) fireAndForget(
 	d *database.Delivery,
 	res attemptResult,
 ) {
+	c.eng.observeAttempt(d.Target.Type, res.elapsed())
+
 	c.eng.recordResult(
 		webhookDB, d, 1, res.success,
 		res.statusCode, res.respBody, res.errMsg,
@@ -82,7 +84,7 @@ func (c *httpCore) fireAndForget(
 
 	if res.success {
 		c.eng.updateDeliveryStatus(
-			webhookDB, d,
+			webhookDB, d, d.Target.Type,
 			database.DeliveryStatusDelivered,
 		)
 
@@ -90,7 +92,8 @@ func (c *httpCore) fireAndForget(
 	}
 
 	c.eng.updateDeliveryStatus(
-		webhookDB, d, database.DeliveryStatusFailed,
+		webhookDB, d, d.Target.Type,
+		database.DeliveryStatusFailed,
 	)
 }
 
@@ -107,10 +110,17 @@ func (c *httpCore) withRetry(
 		return
 	}
 
+	// Allow may have moved the breaker to half-open, and the
+	// attempt below may open or close it, so the gauge is
+	// republished on every exit from here.
+	defer c.publishCircuitState(d.Target.Type)
+
 	attemptNum := task.AttemptNum
 
 	res := attempt()
 
+	c.eng.observeAttempt(d.Target.Type, res.elapsed())
+
 	c.eng.recordResult(
 		webhookDB, d, attemptNum, res.success,
 		res.statusCode, res.respBody, res.errMsg,
@@ -121,7 +131,7 @@ func (c *httpCore) withRetry(
 		cb.RecordSuccess()
 
 		c.eng.updateDeliveryStatus(
-			webhookDB, d,
+			webhookDB, d, d.Target.Type,
 			database.DeliveryStatusDelivered,
 		)
 
@@ -146,6 +156,8 @@ func (c *httpCore) circuitBreakerBlock(
 		return false
 	}
 
+	defer c.publishCircuitState(d.Target.Type)
+
 	remaining := cb.CooldownRemaining()
 
 	c.eng.log.Info(
@@ -157,7 +169,7 @@ func (c *httpCore) circuitBreakerBlock(
 	)
 
 	c.eng.updateDeliveryStatus(
-		webhookDB, d,
+		webhookDB, d, d.Target.Type,
 		database.DeliveryStatusRetrying,
 	)
 
@@ -177,7 +189,7 @@ func (c *httpCore) handleRetry(
 ) {
 	if attemptNum >= maxRetries {
 		c.eng.updateDeliveryStatus(
-			webhookDB, d,
+			webhookDB, d, d.Target.Type,
 			database.DeliveryStatusFailed,
 		)
 
@@ -185,7 +197,8 @@ func (c *httpCore) handleRetry(
 	}
 
 	c.eng.updateDeliveryStatus(
-		webhookDB, d, database.DeliveryStatusRetrying,
+		webhookDB, d, d.Target.Type,
+		database.DeliveryStatusRetrying,
 	)
 
 	backoff := calcBackoff(attemptNum)
@@ -215,6 +228,28 @@ func (c *httpCore) getCircuitBreaker(
 	return cb
 }
 
+// publishCircuitState recounts this core's open breakers and
+// publishes the gauge. Each core holds the breakers of exactly one
+// target type, so the recount is over that type's targets alone.
+// Counting rather than adjusting a delta keeps the gauge honest
+// however a breaker changed state.
+func (c *httpCore) publishCircuitState(
+	targetType database.TargetType,
+) {
+	open := 0
+
+	c.circuitBreakers.Range(func(_, val any) bool {
+		cb, ok := val.(*CircuitBreaker)
+		if ok && cb.State() == CircuitOpen {
+			open++
+		}
+
+		return true
+	})
+
+	c.eng.mtr.SetCircuitBreakersOpen(targetType, open)
+}
+
 // remainingBackoff returns how long remains of the backoff
 // window for the last attempt of a recovered retrying
 // delivery. It implements rescheduler.
@@ -302,7 +337,8 @@ func (t *httpTarget) Deliver(
 		)
 
 		t.eng.updateDeliveryStatus(
-			webhookDB, d, database.DeliveryStatusFailed,
+			webhookDB, d, d.Target.Type,
+			database.DeliveryStatusFailed,
 		)
 
 		return

internal/delivery/target_log.go

@@ -2,6 +2,7 @@ package delivery
 
 import (
 	"context"
+	"time"
 
 	"gorm.io/gorm"
 	"sneak.berlin/go/webhooker/internal/database"
@@ -34,6 +35,8 @@ func (t *logTarget) Deliver(
 	_ *Task,
 	_ Scheduler,
 ) {
+	start := time.Now()
+
 	t.eng.log.Info(
 		"webhook event delivered to log target",
 		"delivery_id", d.ID,
@@ -48,11 +51,17 @@ func (t *logTarget) Deliver(
 		"body", d.Event.Body,
 	)
 
+	elapsed := time.Since(start)
+
+	t.eng.observeAttempt(d.Target.Type, elapsed)
+
 	t.eng.recordResult(
-		webhookDB, d, 1, true, 0, "", "", 0,
+		webhookDB, d, 1, true, 0, "", "",
+		elapsed.Milliseconds(),
 	)
 
 	t.eng.updateDeliveryStatus(
-		webhookDB, d, database.DeliveryStatusDelivered,
+		webhookDB, d, d.Target.Type,
+		database.DeliveryStatusDelivered,
 	)
 }

internal/delivery/target_redact.go

@@ -0,0 +1,256 @@
+package delivery
+
+import (
+	"net/url"
+	"slices"
+	"strings"
+
+	"sneak.berlin/go/webhooker/internal/database"
+)
+
+// RedactionMarker stands in for a target credential found in
+// text the target's remote peer chose.
+const RedactionMarker = "(redacted)"
+
+// Redactor removes one target's own credential material from
+// text that target's remote peer chose: a delivery response
+// body, or a delivery error stored before the delivery path
+// learned to mask the URLs it embeds.
+//
+// It removes byte-identical echoes of strings taken from the
+// target's stored configuration, and nothing else. Anything
+// the remote re-encodes survives: JSON "\/" escaping (what
+// PHP's json_encode emits by default), percent-encoding, HTML
+// entities, and an echo of only part of a path. It cannot
+// remove a secret the remote invented.
+//
+// The zero Redactor removes nothing, which is what a caller
+// holding no target for a delivery gets.
+type Redactor struct {
+	secrets []string
+}
+
+// NewRedactor builds the redactor for one target.
+func NewRedactor(t *database.Target) Redactor {
+	secrets := targetSecrets(t)
+
+	// Longest first, so replacing a secret that is contained
+	// in a longer one cannot leave a fragment of the longer
+	// one behind. Configured headers arrive in map order, so
+	// the sort is also what makes the result deterministic.
+	slices.SortFunc(secrets, func(a, b string) int {
+		if d := len(b) - len(a); d != 0 {
+			return d
+		}
+
+		return strings.Compare(a, b)
+	})
+
+	return Redactor{secrets: secrets}
+}
+
+// Redact replaces every occurrence of the target's credential
+// material in s.
+func (r Redactor) Redact(s string) string {
+	if s == "" {
+		return s
+	}
+
+	for _, secret := range r.secrets {
+		s = strings.ReplaceAll(s, secret, RedactionMarker)
+	}
+
+	return s
+}
+
+// RedactCut redacts s, which its caller has already cut to a
+// byte budget, and additionally drops any tail of s that is a
+// proper prefix of a secret.
+//
+// The cut lands wherever the remote's padding puts it, so the
+// remote chooses where inside the credential it falls. The
+// severed prefix left behind equals no secret, so plain
+// Redact would render it verbatim.
+func (r Redactor) RedactCut(s string) string {
+	s = r.Redact(s)
+
+	if n := r.secretPrefixSuffix(s); n > 0 {
+		return s[:len(s)-n] + RedactionMarker
+	}
+
+	return s
+}
+
+// secretPrefixSuffix returns the length of the longest suffix
+// of s that is a proper prefix of one of the secrets, or 0
+// when there is none.
+func (r Redactor) secretPrefixSuffix(s string) int {
+	longest := 0
+
+	for _, secret := range r.secrets {
+		// Proper prefixes only: a whole secret at the tail was
+		// already replaced by Redact.
+		n := min(len(secret)-1, len(s))
+		for ; n > longest; n-- {
+			if strings.HasSuffix(s, secret[:n]) {
+				longest = n
+
+				break
+			}
+		}
+	}
+
+	return longest
+}
+
+// targetSecrets returns the credential-bearing strings a
+// target's configuration carries.
+//
+// The destination URL contributes. Its path, query and
+// userinfo are the credential for both target types that have
+// one — an incoming-webhook URL is a bearer token, which is
+// why MaskURL elides exactly those parts — and they are the
+// material this service actually sends, so a remote that
+// echoes the request back echoes them.
+//
+// Configured request headers contribute their values, but
+// only for the credential-shaped names isCredentialHeaderName
+// picks out. That is the same class-based rule applied to
+// URLs: an echoed Accept or User-Agent still renders, an
+// echoed Authorization does not.
+func targetSecrets(t *database.Target) []string {
+	if t == nil {
+		return nil
+	}
+
+	switch t.Type {
+	case database.TargetTypeSlack:
+		cfg, err := parseSlackConfig(t.Config)
+		if err != nil {
+			return nil
+		}
+
+		return urlSecrets(cfg.WebhookURL)
+	case database.TargetTypeHTTP:
+		cfg, err := parseHTTPConfig(t.Config)
+		if err != nil {
+			return nil
+		}
+
+		return append(
+			urlSecrets(cfg.URL),
+			headerSecrets(cfg.Headers)...,
+		)
+	case database.TargetTypeDatabase, database.TargetTypeLog:
+		// Neither has a destination URL, so neither has
+		// anything to redact.
+		return nil
+	default:
+		return nil
+	}
+}
+
+// urlSecrets returns the substrings of a destination URL that
+// must not survive into a rendered page: the whole URL, the
+// parts of it MaskURL elides, and any userinfo.
+//
+// No length floor is applied to the path. A short path is
+// treated as a credential exactly like a long one, because
+// the field takes an arbitrary URL and no segment can be
+// assumed non-secret — the same rule MaskURL applies.
+func urlSecrets(raw string) []string {
+	raw = strings.TrimSpace(raw)
+	if raw == "" {
+		return nil
+	}
+
+	secrets := []string{raw}
+
+	parsed, err := url.Parse(raw)
+	if err != nil {
+		return secrets
+	}
+
+	if parsed.Path != "" && parsed.Path != "/" {
+		requestURI := parsed.RequestURI()
+		secrets = append(secrets, requestURI)
+
+		if escaped := parsed.EscapedPath(); escaped != requestURI {
+			secrets = append(secrets, escaped)
+		}
+	}
+
+	if parsed.User != nil {
+		secrets = append(secrets, parsed.User.String())
+
+		if pw, ok := parsed.User.Password(); ok && pw != "" {
+			secrets = append(secrets, pw)
+		}
+	}
+
+	return secrets
+}
+
+// minHeaderSecretBytes is the shortest header value treated as
+// a credential. Unlike a URL path, a header value can be a
+// couple of bytes long, and redacting those would scatter the
+// marker through ordinary response text for no gain.
+const minHeaderSecretBytes = 4
+
+// headerSecrets returns the values of the configured headers
+// whose names are credential-shaped.
+func headerSecrets(headers map[string]string) []string {
+	var secrets []string
+
+	for name, value := range headers {
+		value = strings.TrimSpace(value)
+		if len(value) < minHeaderSecretBytes {
+			continue
+		}
+
+		if isCredentialHeaderName(name) {
+			secrets = append(secrets, value)
+		}
+	}
+
+	return secrets
+}
+
+// isCredentialHeaderName classifies a header by its name. The
+// value is never inspected, so the rule is the same
+// class-based one MaskURL applies to a destination URL.
+//
+// The fragments are short on purpose, and match anywhere in
+// the name, so abbreviations an operator might use are covered
+// too: X-Sig, X-Pass, X-HMAC. That over-matches — a header
+// named X-Design contains "sig" — and over-matching is the
+// safe direction here: the cost is a marker where an echoed
+// header value would have rendered.
+func isCredentialHeaderName(name string) bool {
+	name = strings.ToLower(strings.TrimSpace(name))
+
+	// Names that carry a credential by definition.
+	switch name {
+	case "authorization", "proxy-authorization", "cookie":
+		return true
+	}
+
+	// What operators call their own credential headers:
+	// X-Api-Key, X-Hub-Signature, X-Auth-Token.
+	for _, fragment := range []string{
+		"auth",
+		"credential",
+		"hmac",
+		"key",
+		"pass",
+		"secret",
+		"sig",
+		"token",
+	} {
+		if strings.Contains(name, fragment) {
+			return true
+		}
+	}
+
+	return false
+}

internal/delivery/target_redact_test.go

@@ -0,0 +1,246 @@
+package delivery_test
+
+import (
+	"net/url"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"sneak.berlin/go/webhooker/internal/database"
+	"sneak.berlin/go/webhooker/internal/delivery"
+)
+
+// The secret path segments of a Slack incoming webhook URL.
+const (
+	redactSecretPath = "/services/T11111111/B11111111/" +
+		"YYYYYYYYYYYYYYYYYYYYYYYY"
+	redactWebhookURL = "https://hooks.slack.com" +
+		redactSecretPath
+)
+
+func TestRedactor_RemovesSlackWebhookURL(t *testing.T) {
+	t.Parallel()
+
+	r := delivery.NewRedactor(&database.Target{
+		Type:   database.TargetTypeSlack,
+		Config: `{"webhookUrl":"` + redactWebhookURL + `"}`,
+	})
+
+	got := r.Redact("no_service for " + redactWebhookURL)
+
+	assert.NotContains(t, got, redactSecretPath)
+	assert.NotContains(t, got, "T11111111")
+
+	// One marker, not a marker with the host left in front of
+	// it: the whole URL is replaced before the path it
+	// contains, which is what sorting the secrets longest
+	// first buys.
+	assert.Equal(
+		t,
+		"no_service for "+delivery.RedactionMarker,
+		got,
+	)
+}
+
+// TestRedactor_RemovesSecretSeveredByACut covers the input the
+// redactor exists for: text cut to a byte budget with the
+// credential straddling the cut. The remote chooses the
+// padding, so it chooses where the cut lands inside the
+// credential, and the severed prefix that remains equals no
+// secret.
+func TestRedactor_RemovesSecretSeveredByACut(t *testing.T) {
+	t.Parallel()
+
+	r := delivery.NewRedactor(&database.Target{
+		Type:   database.TargetTypeSlack,
+		Config: `{"webhookUrl":"` + redactWebhookURL + `"}`,
+	})
+
+	// Every cut position inside the credential, not just a
+	// convenient one.
+	for n := 1; n < len(redactWebhookURL); n++ {
+		severed := redactWebhookURL[:n]
+		cut := "padding " + severed
+
+		got := r.RedactCut(cut)
+
+		assert.Equal(
+			t,
+			"padding "+delivery.RedactionMarker,
+			got,
+			"cut after %d bytes of the credential", n,
+		)
+	}
+}
+
+// TestRedactor_RedactsCredentialShapedHeaderValues pins the
+// class-based header rule: a header whose name says credential
+// has its value redacted, and a routine header does not, so
+// ordinary response content survives.
+func TestRedactor_RedactsCredentialShapedHeaderValues(
+	t *testing.T,
+) {
+	t.Parallel()
+
+	r := delivery.NewRedactor(&database.Target{
+		Type: database.TargetTypeHTTP,
+		Config: `{"url":"https://example.com/in",` +
+			`"headers":{` +
+			`"Authorization":"Bearer AAAAAAAAAAAA",` +
+			`"Cookie":"session=BBBBBBBBBBBB",` +
+			`"X-Api-Key":"CCCCCCCCCCCC",` +
+			`"X-Hub-Signature":"sha256=DDDDDDDDDDDD",` +
+			`"X-Sig":"EEEEEEEEEEEE",` +
+			`"X-Pass":"FFFFFFFFFFFF",` +
+			`"X-HMAC":"GGGGGGGGGGGG",` +
+			`"X-Credential":"HHHHHHHHHHHH",` +
+			`"Accept":"application/json",` +
+			`"User-Agent":"webhooker/1.0"}}`,
+	})
+
+	for _, secret := range []string{
+		"Bearer AAAAAAAAAAAA",
+		"session=BBBBBBBBBBBB",
+		"CCCCCCCCCCCC",
+		"sha256=DDDDDDDDDDDD",
+		// Abbreviated names an operator might use.
+		"EEEEEEEEEEEE",
+		"FFFFFFFFFFFF",
+		"GGGGGGGGGGGG",
+		"HHHHHHHHHHHH",
+	} {
+		got := r.Redact("echo: " + secret)
+
+		assert.Equal(
+			t,
+			"echo: "+delivery.RedactionMarker,
+			got,
+			secret,
+		)
+	}
+
+	const routine = "Accept: application/json, " +
+		"User-Agent: webhooker/1.0"
+
+	assert.Equal(t, routine, r.Redact(routine))
+}
+
+// TestRedactor_IgnoresVeryShortHeaderValues pins the floor
+// under a header value. Redacting a two-byte value would put
+// the marker through every response that happens to contain
+// those bytes.
+func TestRedactor_IgnoresVeryShortHeaderValues(t *testing.T) {
+	t.Parallel()
+
+	r := delivery.NewRedactor(&database.Target{
+		Type: database.TargetTypeHTTP,
+		Config: `{"url":"https://example.com/in",` +
+			`"headers":{"X-Api-Key":"ab"}}`,
+	})
+
+	const response = "rabbit"
+
+	assert.Equal(t, response, r.Redact(response))
+}
+
+// TestRedactor_RemovesBarePath covers a remote that echoes
+// only the request path rather than the whole URL. The path
+// segments are the credential on their own.
+func TestRedactor_RemovesBarePath(t *testing.T) {
+	t.Parallel()
+
+	r := delivery.NewRedactor(&database.Target{
+		Type:   database.TargetTypeSlack,
+		Config: `{"webhookUrl":"` + redactWebhookURL + `"}`,
+	})
+
+	got := r.Redact("POST " + redactSecretPath + " 404")
+
+	assert.NotContains(t, got, redactSecretPath)
+	assert.Equal(
+		t,
+		"POST "+delivery.RedactionMarker+" 404",
+		got,
+	)
+}
+
+// TestRedactor_RemovesHTTPURLQueryAndUserinfo covers the HTTP
+// target, whose destination is an arbitrary URL: the query
+// string and the userinfo carry credentials as readily as the
+// path does.
+func TestRedactor_RemovesHTTPURLQueryAndUserinfo(t *testing.T) {
+	t.Parallel()
+
+	// Assembled rather than written out, so the literal is
+	// not itself a credential-shaped string.
+	dest := url.URL{
+		Scheme:   "https",
+		User:     url.UserPassword("user", "hunter2"),
+		Host:     "example.com",
+		Path:     "/in",
+		RawQuery: "token=s3cr3t",
+	}
+	raw := dest.String()
+
+	r := delivery.NewRedactor(&database.Target{
+		Type:   database.TargetTypeHTTP,
+		Config: `{"url":"` + raw + `"}`,
+	})
+
+	for _, echoed := range []string{
+		raw,
+		"/in?token=s3cr3t",
+		"hunter2",
+	} {
+		got := r.Redact("rejected: " + echoed)
+
+		assert.NotContains(t, got, "s3cr3t", echoed)
+		assert.NotContains(t, got, "hunter2", echoed)
+		assert.Contains(
+			t, got, delivery.RedactionMarker, echoed,
+		)
+	}
+}
+
+// TestRedactor_LeavesUnrelatedTextAlone pins that the
+// redactor matches literally: it does not guess at what a
+// secret looks like, so ordinary response content survives.
+func TestRedactor_LeavesUnrelatedTextAlone(t *testing.T) {
+	t.Parallel()
+
+	const response = "ok=false error=channel_not_found"
+
+	r := delivery.NewRedactor(&database.Target{
+		Type:   database.TargetTypeSlack,
+		Config: `{"webhookUrl":"` + redactWebhookURL + `"}`,
+	})
+
+	assert.Equal(t, response, r.Redact(response))
+}
+
+// TestRedactor_ZeroValueAndConfiglessTargets pins that a
+// caller with no target, an unparseable config, or a target
+// type with no destination URL gets a redactor that changes
+// nothing rather than one that panics.
+func TestRedactor_ZeroValueAndConfiglessTargets(t *testing.T) {
+	t.Parallel()
+
+	const text = "some response body"
+
+	var zero delivery.Redactor
+
+	assert.Equal(t, text, zero.Redact(text))
+	assert.Equal(t, text, delivery.NewRedactor(nil).Redact(text))
+
+	for _, tgt := range []database.Target{
+		{Type: database.TargetTypeLog},
+		{Type: database.TargetTypeDatabase},
+		{Type: database.TargetTypeSlack, Config: "not json"},
+		{Type: database.TargetTypeHTTP, Config: ""},
+	} {
+		assert.Equal(
+			t, text,
+			delivery.NewRedactor(&tgt).Redact(text),
+			tgt.Type,
+		)
+	}
+}

internal/delivery/target_slack.go

@@ -101,7 +101,8 @@ func (t *slackTarget) failConfig(
 	)
 
 	t.eng.updateDeliveryStatus(
-		webhookDB, d, database.DeliveryStatusFailed,
+		webhookDB, d, d.Target.Type,
+		database.DeliveryStatusFailed,
 	)
 }
 

internal/gormlog/firstboot_test.go

@@ -0,0 +1,229 @@
+package gormlog_test
+
+import (
+	"context"
+	"database/sql"
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"go.uber.org/fx"
+	"go.uber.org/fx/fxtest"
+	_ "modernc.org/sqlite" // Pure Go SQLite driver.
+	"sneak.berlin/go/webhooker/internal/config"
+	"sneak.berlin/go/webhooker/internal/database"
+	"sneak.berlin/go/webhooker/internal/globals"
+	"sneak.berlin/go/webhooker/internal/logger"
+	"sneak.berlin/go/webhooker/internal/session"
+)
+
+// argon2Prefix opens every encoded Argon2id hash this service
+// produces. It is asserted on separately from the hash itself, so that
+// a change to the password encoding cannot quietly turn the hash
+// assertion into a comparison against a string the log never held.
+const argon2Prefix = "$argon2id$"
+
+// settingsInsert and usersInsert are the two statements a first boot
+// runs that carry a secret. The sqlite dialector quotes identifiers
+// with backticks.
+const (
+	settingsInsert = "INSERT INTO `settings`"
+	usersInsert    = "INSERT INTO `users`"
+)
+
+// captureStdoutToFile redirects os.Stdout into a file for the rest of
+// the test and returns a function that reads back everything written
+// to it.
+//
+// A file rather than a pipe: internal/logger writes synchronously to
+// whatever os.Stdout is when it builds its handler, so once fx's start
+// returns, every byte the boot produced is already in the file and no
+// draining goroutine is needed to prove it. Redirecting the variable
+// before the application is built is what puts the service logger —
+// and therefore the GORM adapter, which writes through it — into the
+// capture.
+//
+// The redirect also decides the handler: a regular file is not a
+// character device, so internal/logger installs its JSON handler, the
+// one it installs in production under a log collector.
+func captureStdoutToFile(t *testing.T) func() string {
+	t.Helper()
+
+	path := filepath.Join(t.TempDir(), "stdout.log")
+
+	//nolint:gosec // The path is this test's own t.TempDir().
+	f, err := os.Create(path)
+	require.NoError(t, err)
+
+	orig := os.Stdout
+	os.Stdout = f
+
+	t.Cleanup(func() {
+		os.Stdout = orig
+		_ = f.Close()
+	})
+
+	return func() string {
+		require.NoError(t, f.Sync())
+
+		//nolint:gosec // As above.
+		b, readErr := os.ReadFile(path)
+		require.NoError(t, readErr)
+
+		return string(b)
+	}
+}
+
+// firstBootSecrets are the two values a first boot generates and
+// stores, read back out of the database.
+type firstBootSecrets struct {
+	sessionKey   string
+	passwordHash string
+}
+
+// readFirstBootSecrets reads those two secrets straight out of the
+// SQLite file with database/sql rather than through GORM, so that
+// reading them cannot itself add a line to the log under test.
+func readFirstBootSecrets(
+	t *testing.T, dataDir string,
+) firstBootSecrets {
+	t.Helper()
+
+	db, err := sql.Open("sqlite", filepath.Join(
+		dataDir, "webhooker.db",
+	))
+	require.NoError(t, err)
+
+	defer func() { require.NoError(t, db.Close()) }()
+
+	ctx := context.Background()
+
+	var got firstBootSecrets
+
+	require.NoError(t, db.QueryRowContext(
+		ctx, `SELECT value FROM settings WHERE key = 'session_key'`,
+	).Scan(&got.sessionKey))
+
+	require.NoError(t, db.QueryRowContext(
+		ctx, `SELECT password FROM users WHERE username = 'admin'`,
+	).Scan(&got.passwordHash))
+
+	require.NotEmpty(t, got.sessionKey)
+	require.Contains(t, got.passwordHash, argon2Prefix)
+
+	return got
+}
+
+// bootAtDebug starts and stops the real application graph against
+// dataDir with DEBUG=true, and returns everything it wrote to standard
+// output.
+//
+// config.New reads DEBUG from the environment exactly as the binary
+// does, internal/logger builds the handler it builds in production,
+// database.New runs the migrations and creates the admin user, and
+// session.New takes the session key. Those four are the whole of the
+// path that writes either secret.
+func bootAtDebug(t *testing.T, dataDir string) string {
+	t.Helper()
+
+	t.Setenv("DEBUG", "true")
+	t.Setenv("DATA_DIR", dataDir)
+
+	read := captureStdoutToFile(t)
+
+	var sess *session.Session
+
+	app := fxtest.New(
+		t,
+		fx.Provide(
+			globals.New,
+			logger.New,
+			config.New,
+			database.New,
+			session.New,
+		),
+		fx.Populate(&sess),
+	)
+
+	app.RequireStart()
+	app.RequireStop()
+
+	return read()
+}
+
+// requireFirstBootWasLogged is the non-vacuity half of the test below.
+// Without it a build that logged no SQL at all, or that never reached
+// DEBUG, would satisfy every absence assertion.
+func requireFirstBootWasLogged(t *testing.T, out string) {
+	t.Helper()
+
+	require.Contains(
+		t, out, `"level":"DEBUG"`,
+		"DEBUG=true did not reach the logger",
+	)
+	require.Contains(
+		t, out, settingsInsert,
+		"the session key INSERT was not logged, so its absence "+
+			"proves nothing",
+	)
+	require.Contains(
+		t, out, usersInsert,
+		"the admin user INSERT was not logged, so its absence "+
+			"proves nothing",
+	)
+}
+
+// TestFirstBootAtDebug_LogsNeitherSecret is the definition of done.
+//
+// A first boot is the only boot that writes either secret. The
+// settings INSERT carries the base64 session encryption key, which is
+// the whole of the session security model: anyone holding it can forge
+// an authenticated session cookie. The users INSERT carries the admin
+// account's Argon2id hash. Under interpolated statement logging both
+// landed in the log an operator diagnosing a startup problem pastes
+// into an issue.
+//
+// The secrets are read back out of the database file afterwards, so
+// the assertions are made against the values this boot actually
+// generated rather than against a pattern that might not match them.
+//
+// What this test does not cover: the initial admin password itself,
+// which internal/database logs once in the clear, on purpose, because
+// that line is the only place an operator ever sees it. That is a
+// separate decision from the SQL log, and it is documented in the
+// README rather than asserted here.
+//
+// Not parallel: it redirects os.Stdout and sets environment variables,
+// both process-global.
+//
+//nolint:paralleltest // Deliberately sequential; see above.
+func TestFirstBootAtDebug_LogsNeitherSecret(t *testing.T) {
+	dataDir := t.TempDir()
+
+	// An empty DATA_DIR is what makes this a first boot: with a
+	// database already in place neither INSERT runs.
+	entries, err := os.ReadDir(dataDir)
+	require.NoError(t, err)
+	require.Empty(t, entries, "DATA_DIR was not empty")
+
+	out := bootAtDebug(t, dataDir)
+
+	requireFirstBootWasLogged(t, out)
+
+	secrets := readFirstBootSecrets(t, dataDir)
+
+	assert.NotContains(
+		t, out, secrets.sessionKey,
+		"the session encryption key reached the debug log",
+	)
+	assert.NotContains(
+		t, out, secrets.passwordHash,
+		"the admin password hash reached the debug log",
+	)
+	assert.NotContains(
+		t, out, argon2Prefix,
+		"an encoded Argon2id hash reached the debug log",
+	)
+}

internal/gormlog/gormlog.go

@@ -17,6 +17,10 @@
 // level the operator controls, they are shaped by whichever handler
 // internal/logger selected, and every value a client can influence is
 // spent through logfield.Truncate.
+//
+// It also logs no bound value at all. See ParamsFilter: the statement
+// is written with its placeholders intact, at every level, so the
+// values a statement carries never reach the log in the first place.
 package gormlog
 
 import (
@@ -26,6 +30,7 @@ import (
 	"log/slog"
 	"time"
 
+	"gorm.io/gorm"
 	gormlogger "gorm.io/gorm/logger"
 	"sneak.berlin/go/webhooker/internal/logfield"
 )
@@ -47,8 +52,14 @@ type Logger struct {
 }
 
 // Interface compliance is asserted here rather than discovered at the
-// gorm.Open call sites.
-var _ gormlogger.Interface = (*Logger)(nil)
+// gorm.Open call sites. gorm.ParamsFilter is the optional half: GORM
+// type-asserts for it and silently keeps interpolating if it is
+// missing, so losing it would cost no build error and no test that
+// does not look at the emitted SQL.
+var (
+	_ gormlogger.Interface = (*Logger)(nil)
+	_ gorm.ParamsFilter    = (*Logger)(nil)
+)
 
 // New returns a GORM logger that writes through log.
 func New(log *slog.Logger) *Logger {
@@ -71,6 +82,46 @@ func (l *Logger) LogMode(gormlogger.LogLevel) gormlogger.Interface {
 	return l
 }
 
+// ParamsFilter drops every bound value before GORM renders a statement
+// for the log, so what is logged is the statement's shape — its
+// placeholders — and never the values in it.
+//
+// GORM builds the string it hands to Trace by calling
+// Dialector.Explain(sql, vars...), which substitutes each value into
+// the statement. Discarding vars here leaves the '?' placeholders in
+// place, because ExplainSQL only substitutes while it still has a
+// value for the next one. That happens before Trace is reached, so it
+// holds on all three of its arms: the failed statement, the slow one,
+// and the routine one an operator sees at DEBUG.
+//
+// This is the whole of the fix, and it is deliberately unconditional
+// rather than a list of tables to redact. At first boot the two
+// statements that carry a secret are the INSERT into settings holding
+// the base64 session key — which is the entire session security model,
+// since anyone with it can mint a valid cookie — and the INSERT into
+// users holding the Argon2id hash. A denylist would have had to be
+// extended by hand for every table added afterwards, and the cost of
+// missing one is a credential in a log that gets pasted into issues.
+//
+// What is given up is the ability to read a value out of the log. The
+// statement, the table, the error and the row count are all still
+// there, which is what identifies a failing statement; reproducing it
+// needs the values, and those an operator now gets from the database
+// rather than from the log.
+//
+// One GORM path does not consult this: (*gorm.DB).Scan records the
+// statement through gorm's own traceRecorder, which does not implement
+// this interface. No production code path calls it; its one caller is
+// internal/database/database_test.go:91, whose SELECT 1 binds nothing.
+// scan_guard_test.go fails if a non-test file calls it.
+// (*gorm.DB).Pluck, Row and Raw all run through the normal callback
+// processor and are filtered.
+func (l *Logger) ParamsFilter(
+	_ context.Context, sql string, _ ...any,
+) (string, []any) {
+	return sql, nil
+}
+
 // Info logs one of GORM's own informational messages.
 func (l *Logger) Info(
 	ctx context.Context, msg string, data ...any,
@@ -93,9 +144,9 @@ func (l *Logger) Error(
 }
 
 // Trace reports the outcome of a single statement. GORM calls it for
-// every statement it runs, so the cheap paths stay cheap: fc()
-// renders the interpolated SQL and is called only on a branch that
-// will actually emit.
+// every statement it runs, so the cheap paths stay cheap: fc() renders
+// the statement — with placeholders, per ParamsFilter — and is called
+// only on a branch that will actually emit.
 //
 // The arms are ordered exactly as GORM's own Trace orders them —
 // non-record-not-found error, then slow, then the routine case — so

internal/gormlog/gormlog_test.go

@@ -232,7 +232,7 @@ func TestSlowRecordNotFound_IsStillReportedSlow(t *testing.T) {
 				require.ErrorIs(t, err, gorm.ErrRecordNotFound)
 
 				assert.Contains(
-					t, buf.String(), "slow sql statement",
+					t, buf.String(), slowLine,
 					"a slow statement that missed was not "+
 						"reported as slow",
 				)
@@ -284,9 +284,11 @@ func TestRecordNotFoundFlood_DoesNotGrowWithInput(t *testing.T) {
 }
 
 // TestStatementError_LineIsBounded covers the branch that does log.
-// A driver error is not ErrRecordNotFound, so the interpolated
-// statement is written — and on an insert the interpolated value is
-// still whatever the client supplied.
+// A driver error is not ErrRecordNotFound, so the statement is
+// written, and the driver's own error text can quote what the client
+// supplied. The statement's parameters are no longer part of that —
+// see TestBoundValues_NeverReachTheLog — but the budget is what holds
+// the line when the statement itself, or the error, is the long part.
 func TestStatementError_LineIsBounded(t *testing.T) {
 	t.Parallel()
 
@@ -313,7 +315,7 @@ func TestStatementError_LineIsBounded(t *testing.T) {
 				require.Error(t, err)
 
 				assert.Contains(
-					t, buf.String(), "sql statement failed",
+					t, buf.String(), errorLine,
 				)
 				assertBounded(t, buf.String())
 			})
@@ -329,22 +331,22 @@ func TestStatementError_LineIsBounded(t *testing.T) {
 //     and would have cost this report, which is the one thing GORM's
 //     logger gave an operator that nothing else in this service does.
 //   - routine. The branch an operator reaches by turning the level
-//     down to DEBUG: every statement is reported, so every
-//     statement's interpolated parameters have to be bounded too.
+//     down to DEBUG: every statement is reported, so every statement
+//     has to be bounded too.
 func TestSucceedingStatement_LineIsBoundedOnEitherArm(t *testing.T) {
 	t.Parallel()
 
-	// "sql statement" is a substring of "slow sql statement", so the
-	// routine arm carries notWant as well: Contains alone cannot tell
-	// the two arms apart in that direction.
+	// routineLine is a substring of slowLine, so the routine arm
+	// carries notWant as well: Contains alone cannot tell the two arms
+	// apart in that direction.
 	arms := []struct {
 		name    string
 		slow    time.Duration
 		want    string
 		notWant string
 	}{
-		{"slow", alwaysSlow, "slow sql statement", ""},
-		{"routine", neverSlow, "sql statement", "slow sql statement"},
+		{"slow", alwaysSlow, slowLine, ""},
+		{"routine", neverSlow, routineLine, slowLine},
 	}
 
 	for _, a := range arms {

internal/gormlog/scan_guard_test.go

@@ -0,0 +1,260 @@
+package gormlog_test
+
+import (
+	"fmt"
+	"go/ast"
+	"go/parser"
+	"go/token"
+	"io/fs"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+// minNonTestFiles guards the walk below against passing because it
+// found nothing to look at. The tree held 60 non-test .go files when
+// this was written.
+const minNonTestFiles = 40
+
+// isRowProducer reports whether name is a method that returns a
+// database/sql row handle. GORM's Row and Rows return *sql.Row and
+// *sql.Rows, so Scan on the result of one of them is database/sql's
+// Scan and never (*gorm.DB).Scan.
+func isRowProducer(name string) bool {
+	switch name {
+	case "Row", "Rows", "QueryRow", "QueryRowContext":
+		return true
+	default:
+		return false
+	}
+}
+
+// receiverIsRowHandle reports whether x is syntactically a call to a
+// row producer, which is the only receiver form this check accepts for
+// a Scan.
+func receiverIsRowHandle(x ast.Expr) bool {
+	call, ok := x.(*ast.CallExpr)
+	if !ok {
+		return false
+	}
+
+	sel, ok := call.Fun.(*ast.SelectorExpr)
+	if !ok {
+		return false
+	}
+
+	return isRowProducer(sel.Sel.Name)
+}
+
+// unguardedScans returns the position of every Scan call in file whose
+// receiver is not a row handle. It fails closed: a receiver it cannot
+// resolve syntactically — a local variable, a struct field — is
+// reported rather than assumed safe.
+func unguardedScans(
+	fset *token.FileSet, file *ast.File,
+) []token.Position {
+	var found []token.Position
+
+	ast.Inspect(file, func(n ast.Node) bool {
+		call, ok := n.(*ast.CallExpr)
+		if !ok {
+			return true
+		}
+
+		sel, ok := call.Fun.(*ast.SelectorExpr)
+		if !ok || sel.Sel.Name != "Scan" {
+			return true
+		}
+
+		if !receiverIsRowHandle(sel.X) {
+			found = append(found, fset.Position(sel.Sel.Pos()))
+		}
+
+		return true
+	})
+
+	return found
+}
+
+// moduleRoot walks up from the working directory to the directory
+// holding go.mod.
+func moduleRoot(t *testing.T) string {
+	t.Helper()
+
+	dir, err := os.Getwd()
+	require.NoError(t, err)
+
+	for {
+		_, statErr := os.Stat(filepath.Join(dir, "go.mod"))
+		if statErr == nil {
+			return dir
+		}
+
+		parent := filepath.Dir(dir)
+		require.NotEqual(t, parent, dir, "no go.mod above %s", dir)
+
+		dir = parent
+	}
+}
+
+// skipDir reports whether a directory holds no source this check
+// governs.
+func skipDir(name string) bool {
+	switch name {
+	case ".git", "bin", "node_modules", "testdata":
+		return true
+	default:
+		return false
+	}
+}
+
+// walkNonTestGo parses every non-test .go file under root and returns
+// how many it parsed along with every unguarded Scan it found.
+func walkNonTestGo(t *testing.T, root string) (int, []string) {
+	t.Helper()
+
+	var (
+		parsed int
+		hits   []string
+	)
+
+	fset := token.NewFileSet()
+
+	require.NoError(t, filepath.WalkDir(
+		root,
+		func(path string, d fs.DirEntry, err error) error {
+			if err != nil {
+				return err
+			}
+
+			if d.IsDir() {
+				if skipDir(d.Name()) {
+					return fs.SkipDir
+				}
+
+				return nil
+			}
+
+			if !isNonTestGo(d.Name()) {
+				return nil
+			}
+
+			file, err := parser.ParseFile(fset, path, nil, 0)
+			if err != nil {
+				return err
+			}
+
+			parsed++
+
+			for _, pos := range unguardedScans(fset, file) {
+				hits = append(hits, relPosition(root, pos))
+			}
+
+			return nil
+		},
+	))
+
+	return parsed, hits
+}
+
+// isNonTestGo reports whether a file name is Go source this check
+// governs.
+func isNonTestGo(name string) bool {
+	return strings.HasSuffix(name, ".go") &&
+		!strings.HasSuffix(name, "_test.go")
+}
+
+// relPosition renders pos with its path relative to root, so a failure
+// names the file the way the repository does.
+func relPosition(root string, pos token.Position) string {
+	name := pos.Filename
+
+	rel, err := filepath.Rel(root, name)
+	if err == nil {
+		name = rel
+	}
+
+	return fmt.Sprintf("%s:%d:%d", name, pos.Line, pos.Column)
+}
+
+// TestGormScanIsNeverCalledOutsideTests keeps (*gorm.DB).Scan out of
+// non-test code.
+//
+// It is the one statement path (*Logger).ParamsFilter does not reach:
+// Scan swaps GORM's own trace recorder in for the adapter, and that
+// recorder does not implement gorm.ParamsFilter, so the statement is
+// logged with its values interpolated. The package comment states the
+// limit; this fails when someone adds a call site anyway.
+//
+// The current tree has one caller, internal/database/database_test.go,
+// which this check does not govern: it is test-only and its SELECT 1
+// binds nothing.
+func TestGormScanIsNeverCalledOutsideTests(t *testing.T) {
+	t.Parallel()
+
+	parsed, offenders := walkNonTestGo(t, moduleRoot(t))
+
+	require.GreaterOrEqual(
+		t, parsed, minNonTestFiles,
+		"parsed %d non-test .go files, so this check found "+
+			"nothing to look at", parsed,
+	)
+	require.Empty(
+		t, offenders,
+		"Scan called on a receiver this check cannot show is a "+
+			"database/sql row handle. (*gorm.DB).Scan logs the "+
+			"statement with its bound values interpolated — use "+
+			"Find, Pluck, or Raw(...).Row().Scan instead. A "+
+			"database/sql Scan reached through a variable is "+
+			"reported too; write it as <producer>().Scan rather "+
+			"than widening this check.",
+	)
+}
+
+// scanGuardCase is one planted snippet and whether the check above
+// should report it.
+type scanGuardCase struct {
+	name string
+	body string
+	want int
+}
+
+func scanGuardCases() []scanGuardCase {
+	return []scanGuardCase{
+		{"gorm chain", `db.DB().Raw("SELECT 1").Scan(&v)`, 1},
+		{"gorm receiver", `gdb.Scan(&v)`, 1},
+		{"gorm via variable", "q := gdb.Raw(\"x\")\nq.Scan(&v)", 1},
+		{"gorm model chain", `gdb.Model(&x).Scan(&v)`, 1},
+		{"sql row", `gdb.Raw("SELECT 1").Row().Scan(&v)`, 0},
+		{"sql rows", `gdb.Raw("SELECT 1").Rows().Scan(&v)`, 0},
+		{"unrelated call", `gdb.Find(&v)`, 0},
+	}
+}
+
+// TestScanGuard_ReportsPlantedCalls proves the check fires. Without it
+// a detector that matched nothing would satisfy the walk above no
+// matter what the tree contained.
+func TestScanGuard_ReportsPlantedCalls(t *testing.T) {
+	t.Parallel()
+
+	for _, tc := range scanGuardCases() {
+		t.Run(tc.name, func(t *testing.T) {
+			t.Parallel()
+
+			fset := token.NewFileSet()
+			src := fmt.Sprintf(
+				"package p\n\nfunc f() {\n\t%s\n}\n", tc.body,
+			)
+
+			file, err := parser.ParseFile(
+				fset, tc.name+".go", src, 0,
+			)
+			require.NoError(t, err)
+
+			require.Len(t, unguardedScans(fset, file), tc.want)
+		})
+	}
+}

internal/gormlog/values_test.go

@@ -0,0 +1,185 @@
+package gormlog_test
+
+import (
+	"bytes"
+	"strings"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"gorm.io/gorm"
+)
+
+// secretValue is bound as a parameter by every case below. Nothing
+// else in this package writes it, so finding it in captured output
+// means a bound value was rendered into the log.
+const secretValue = "QQBOUNDVALUEMARKERQQ"
+
+// The three messages Trace emits under, one per arm.
+//
+// routineLine is a substring of slowLine, so a case that wants the
+// routine arm has to rule the slow one out as well rather than rely on
+// Contains alone.
+const (
+	routineLine = "sql statement"
+	slowLine    = "slow sql statement"
+	errorLine   = "sql statement failed"
+)
+
+// boundValueCase is one arm of Trace, driven by a statement that binds
+// secretValue.
+type boundValueCase struct {
+	name  string
+	slow  time.Duration
+	want  string
+	drive func(t *testing.T, gdb *gorm.DB)
+}
+
+// insertSecret returns a driver that inserts one row whose Name is the
+// secret.
+func insertSecret(id string) func(*testing.T, *gorm.DB) {
+	return func(t *testing.T, gdb *gorm.DB) {
+		t.Helper()
+
+		require.NoError(t, gdb.Create(&thing{
+			ID: id, Name: secretValue,
+		}).Error)
+	}
+}
+
+// insertSecretTwice drives the error arm: the same primary key a
+// second time is a UNIQUE constraint failure, which is an error GORM
+// logs with the statement.
+func insertSecretTwice(t *testing.T, gdb *gorm.DB) {
+	t.Helper()
+
+	require.NoError(t, gdb.Create(&thing{
+		ID: secretValue, Name: secretValue,
+	}).Error)
+	require.Error(t, gdb.Create(&thing{
+		ID: secretValue, Name: "other",
+	}).Error)
+}
+
+// selectSecret drives a query whose WHERE clause binds the secret,
+// covering the read side as well as the write side.
+func selectSecret(t *testing.T, gdb *gorm.DB) {
+	t.Helper()
+
+	var got []thing
+
+	require.NoError(
+		t, gdb.Where("name = ?", secretValue).Find(&got).Error,
+	)
+}
+
+func boundValueCases() []boundValueCase {
+	return []boundValueCase{
+		{
+			name: "routine", slow: neverSlow,
+			want: routineLine, drive: insertSecret("routine"),
+		},
+		{
+			name: "slow", slow: alwaysSlow,
+			want: slowLine, drive: insertSecret("slow"),
+		},
+		{
+			name: "error", slow: neverSlow,
+			want: errorLine, drive: insertSecretTwice,
+		},
+		{
+			name: "select", slow: neverSlow,
+			want: routineLine, drive: selectSecret,
+		},
+	}
+}
+
+// TestBoundValues_NeverReachTheLog states the values-off property
+// directly, on each arm of Trace that emits.
+//
+// Truncation is not what is being asserted. A bounded secret is still
+// a secret: the session key is 44 base64 characters and an Argon2id
+// hash under 100, so both fit inside every budget this package
+// applies. What keeps them out is that the adapter logs the
+// statement's shape and discards its parameters — see
+// (*Logger).ParamsFilter — and that has to hold at DEBUG as much as on
+// an error, because DEBUG is the level at which a successful INSERT is
+// written at all.
+//
+// Each case also requires a placeholder in the logged statement.
+// Without that, the absence of the value would be satisfied by a
+// logger that wrote nothing useful.
+func TestBoundValues_NeverReachTheLog(t *testing.T) {
+	t.Parallel()
+
+	for _, tc := range boundValueCases() {
+		for _, h := range handlers() {
+			t.Run(tc.name+"/"+h.name, func(t *testing.T) {
+				t.Parallel()
+
+				var buf bytes.Buffer
+
+				gdb := openDB(t, &buf, h.make(&buf), tc.slow)
+
+				tc.drive(t, gdb)
+
+				assertNoBoundValue(t, buf.String(), tc.want)
+			})
+		}
+	}
+}
+
+// assertNoBoundValue holds one captured arm to the property: it wrote
+// the line it was supposed to write, that line kept its placeholders,
+// and it carried no bound value.
+func assertNoBoundValue(t *testing.T, out, want string) {
+	t.Helper()
+
+	require.Contains(
+		t, out, want,
+		"the arm under test wrote nothing, so the assertions "+
+			"below are vacuous",
+	)
+	assert.NotContains(
+		t, out, secretValue,
+		"a bound parameter was rendered into the log",
+	)
+	assert.Contains(
+		t, out, "?",
+		"the statement was logged without its placeholders",
+	)
+}
+
+// TestInsert_KeepsOnePlaceholderPerBoundValue pins the shape of the
+// INSERT specifically, since that is the statement that carries both
+// first-boot secrets. A statement that dropped one value and kept the
+// other would satisfy the assertions above.
+func TestInsert_KeepsOnePlaceholderPerBoundValue(t *testing.T) {
+	t.Parallel()
+
+	var buf bytes.Buffer
+
+	gdb := openDB(t, &buf, handlers()[0].make(&buf), neverSlow)
+
+	require.NoError(t, gdb.Create(&thing{
+		ID: "m", Name: secretValue,
+	}).Error)
+
+	out := buf.String()
+
+	require.Contains(t, out, "INSERT INTO")
+	assert.NotContains(t, out, secretValue)
+
+	for line := range strings.SplitSeq(out, "\n") {
+		if !strings.Contains(line, "INSERT INTO") {
+			continue
+		}
+
+		assert.GreaterOrEqual(
+			t, strings.Count(line, "?"), 2,
+			"insert logged fewer placeholders than it bound "+
+				"values: %s", line,
+		)
+	}
+}

internal/handlers/delivery_result_view.go

@@ -0,0 +1,169 @@
+package handlers
+
+import (
+	"sneak.berlin/go/webhooker/internal/delivery"
+)
+
+// maxRenderedResponseBytes caps how many bytes of one stored
+// delivery response body reach the event log page.
+//
+// The bound is enforced here and in SQL, because this page's
+// memory profile must not depend on a constant in another
+// package staying where it is, and because rows predating the
+// delivery engine's own cap or restored from an archive are
+// not covered by it at all.
+//
+// It happens to equal that engine cap, so a row written by the
+// current engine reaches this one exactly and is never cut
+// twice. Nothing here may assume the two differ: see view.
+const maxRenderedResponseBytes = 4096
+
+// deliveryResultColumns is the delivery attempt projection.
+// The casts to blob are load-bearing for the same reason they
+// are in eventLogColumns: they make substr and length count
+// bytes rather than characters, and they make SQLite do the
+// cut, so an oversized stored response never becomes a Go
+// string at all.
+const deliveryResultColumns = "delivery_id, attempt_num, success, " +
+	"status_code, error, duration, " +
+	"substr(cast(response_body as blob), 1, ?) AS response_body, " +
+	"length(cast(response_body as blob)) AS response_bytes"
+
+// DeliveryResultView is the display-safe projection of one
+// delivery attempt for the event log page. It carries a
+// capped response body plus the true stored size, so the page
+// can mark a response as truncated without holding the whole
+// thing.
+//
+// Both Error and ResponseBody have been through the target's
+// Redactor. The engine already masks the URL out of the
+// errors it stores, so for errors this is a second line
+// covering rows written before it did; for response bodies it
+// is the only line, and its reach is what
+// delivery.Redactor documents.
+type DeliveryResultView struct {
+	AttemptNum int
+	Success    bool
+
+	// StatusCode is 0 when the attempt never got a response,
+	// which is why the page asks HasStatusCode rather than
+	// printing the number.
+	StatusCode int
+
+	// Error is the stored failure message, redacted.
+	Error string
+
+	// DurationMS is how long the attempt took.
+	DurationMS int64
+
+	// ResponseBody holds at most maxRenderedResponseBytes
+	// bytes of the stored response, redacted. It is remote
+	// content and must only ever be rendered escaped.
+	ResponseBody string
+
+	// ResponseBytes is the size of the stored response body,
+	// before the cut and before redaction. It is what the
+	// remote sent only when ResponseSizeKnown is set.
+	ResponseBytes int64
+
+	// ResponseShownBytes is how much of that the page is
+	// showing. It is the size of the cut, taken before
+	// redaction, so the truncation marker reports what SQLite
+	// returned rather than how much the marker substitution
+	// then changed the length.
+	ResponseShownBytes int
+
+	// ResponseTruncated reports that the body shown may be
+	// incomplete, so the page owes the reader a marker. Every
+	// body that reaches the cap counts, because one the
+	// delivery engine cut at its own equal cap is
+	// indistinguishable from a complete one.
+	ResponseTruncated bool
+
+	// ResponseSizeKnown reports that ResponseBytes is the whole
+	// response the remote sent, so the marker may quote it. It
+	// is false for a body that only reaches the cap, where how
+	// much came after it was never recorded.
+	ResponseSizeKnown bool
+}
+
+// HasStatusCode reports whether the attempt got as far as an
+// HTTP response. A transport failure stores no status code,
+// and rendering that as "0" would read as a real status.
+func (v DeliveryResultView) HasStatusCode() bool {
+	return v.StatusCode != 0
+}
+
+// deliveryResultRow is one row of the delivery attempt
+// projection. Its response body arrives already cut to the
+// cap by SQLite, with the true size beside it.
+type deliveryResultRow struct {
+	DeliveryID    string
+	AttemptNum    int
+	Success       bool
+	StatusCode    int
+	Error         string
+	Duration      int64
+	ResponseBody  []byte
+	ResponseBytes int64
+}
+
+// view projects a loaded row for rendering, stripping the
+// target's own credential out of the two fields a remote peer
+// gets to influence.
+func (r *deliveryResultRow) view(
+	redactor delivery.Redactor,
+) DeliveryResultView {
+	body := r.ResponseBody
+
+	// Two different cuts can have shortened this body, and the
+	// row records only one of them. SQLite cuts here, whenever
+	// the stored value is larger than the cap. The delivery
+	// engine cut earlier, whenever the remote sent more than
+	// its own maxBodyLog — which is this same number, so such a
+	// row stores the cut length as its whole length and nothing
+	// in it separates a response that ended at the cap from one
+	// severed there.
+	//
+	// So a body that reaches the cap is treated as cut either
+	// way. Gating on ResponseBytes alone would assume the two
+	// caps differ, and they do not: under the current engine
+	// that gate never opens.
+	cut := r.ResponseBytes > int64(len(body)) ||
+		len(body) >= maxRenderedResponseBytes
+
+	// The row holds more than the page shows only in the first
+	// of those cases. In the second the stored row is all there
+	// is, and its size is a floor rather than the true one.
+	sizeKnown := r.ResponseBytes > int64(len(body))
+
+	// Only a cut response can have been left mid-sequence,
+	// exactly as with an event body.
+	if cut {
+		body = trimPartialRune(body)
+	}
+
+	// A cut body goes through RedactCut: the remote controls
+	// the padding ahead of a credential it echoes, so it
+	// controls where the cut falls inside that credential, and
+	// the severed prefix left behind matches no secret whole.
+	rendered := string(body)
+	if cut {
+		rendered = redactor.RedactCut(rendered)
+	} else {
+		rendered = redactor.Redact(rendered)
+	}
+
+	return DeliveryResultView{
+		AttemptNum:         r.AttemptNum,
+		Success:            r.Success,
+		StatusCode:         r.StatusCode,
+		Error:              redactor.Redact(r.Error),
+		DurationMS:         r.Duration,
+		ResponseBody:       rendered,
+		ResponseBytes:      r.ResponseBytes,
+		ResponseShownBytes: len(body),
+		ResponseTruncated:  cut,
+		ResponseSizeKnown:  sizeKnown,
+	}
+}

internal/handlers/delivery_result_view_test.go

@@ -0,0 +1,509 @@
+package handlers_test
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"strconv"
+	"strings"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"gorm.io/gorm/clause"
+	"sneak.berlin/go/webhooker/internal/database"
+	"sneak.berlin/go/webhooker/internal/delivery"
+	"sneak.berlin/go/webhooker/internal/handlers"
+	"sneak.berlin/go/webhooker/internal/session"
+)
+
+// responseCap is the number of response bytes the event log
+// page is allowed to render for one delivery attempt.
+const responseCap = handlers.MaxRenderedResponseBytesForTest
+
+// failedAttempt describes the failed delivery every test in
+// this file seeds. The values are distinctive so that finding
+// them in the rendered page cannot be a coincidence.
+const (
+	attemptStatusCode = 502
+	attemptDurationMS = 1234
+	attemptNumber     = 3
+	attemptError      = "upstream returned 502 Bad Gateway"
+)
+
+// seedFailedDelivery records an event, a failed delivery
+// against targetID, and one delivery result carrying the
+// given response body. It returns the delivery.
+func seedFailedDelivery(
+	t *testing.T,
+	dbMgr *database.WebhookDBManager,
+	webhookID, targetID, responseBody string,
+) *database.Delivery {
+	t.Helper()
+
+	webhookDB, err := dbMgr.GetDB(webhookID)
+	require.NoError(t, err)
+
+	event := &database.Event{
+		WebhookID:   webhookID,
+		Method:      http.MethodPost,
+		Body:        `{"test":true}`,
+		ContentType: "application/json",
+	}
+
+	require.NoError(t, webhookDB.Omit(
+		clause.Associations,
+	).Create(event).Error)
+
+	dlv := &database.Delivery{
+		EventID:  event.ID,
+		TargetID: targetID,
+		Status:   database.DeliveryStatusFailed,
+	}
+
+	require.NoError(t, webhookDB.Omit(
+		clause.Associations,
+	).Create(dlv).Error)
+
+	result := &database.DeliveryResult{
+		DeliveryID:   dlv.ID,
+		AttemptNum:   attemptNumber,
+		Success:      false,
+		StatusCode:   attemptStatusCode,
+		ResponseBody: responseBody,
+		Error:        attemptError,
+		Duration:     attemptDurationMS,
+	}
+
+	require.NoError(t, webhookDB.Omit(
+		clause.Associations,
+	).Create(result).Error)
+
+	return dlv
+}
+
+// seedFailureAndRender seeds a failed delivery against a
+// target of the given type and config, and returns the
+// rendered event log page.
+func seedFailureAndRender(
+	t *testing.T,
+	targetType database.TargetType,
+	config, responseBody string,
+) string {
+	t.Helper()
+
+	var (
+		h     *handlers.Handlers
+		sess  *session.Session
+		db    *database.Database
+		dbMgr *database.WebhookDBManager
+	)
+
+	app := newTestApp(t, &h, &sess, &db, &dbMgr)
+	app.RequireStart()
+
+	t.Cleanup(app.RequireStop)
+
+	wh := seedWebhook(t, db)
+	tgt := seedConfiguredTarget(
+		t, db, wh.ID, targetType, config,
+	)
+
+	seedFailedDelivery(t, dbMgr, wh.ID, tgt.ID, responseBody)
+
+	return renderSourceLogsPage(t, h, sess, wh.ID)
+}
+
+// TestHandleSourceLogs_RendersFailedAttempt is the regression
+// test for the reported gap: a failed delivery used to render
+// as the status word alone, so diagnosing it meant opening the
+// per-webhook SQLite file by hand.
+func TestHandleSourceLogs_RendersFailedAttempt(t *testing.T) {
+	t.Parallel()
+
+	body := seedFailureAndRender(
+		t,
+		database.TargetTypeHTTP,
+		`{"url":"https://example.com/hook/abc"}`,
+		"upstream exploded",
+	)
+
+	assert.Contains(
+		t, body, strconv.Itoa(attemptStatusCode),
+		"the attempt's status code must reach the page",
+	)
+	assert.Contains(
+		t, body, attemptError,
+		"the attempt's error must reach the page",
+	)
+	assert.Contains(
+		t, body, strconv.Itoa(attemptDurationMS),
+		"the attempt's duration must reach the page",
+	)
+	assert.Contains(
+		t, body, "Attempt "+strconv.Itoa(attemptNumber),
+		"the attempt number must reach the page",
+	)
+	assert.Contains(
+		t, body, "upstream exploded",
+		"the attempt's response body must reach the page",
+	)
+}
+
+// TestHandleSourceLogs_EscapesResponseBody proves the
+// response body is treated as the untrusted remote content it
+// is. The remote chooses these bytes and the page is rendered
+// inside the operator's authenticated origin, where the
+// application's own CSP allows inline script from 'self'.
+func TestHandleSourceLogs_EscapesResponseBody(t *testing.T) {
+	t.Parallel()
+
+	const payload = `<script>alert("xss")</script>`
+
+	body := seedFailureAndRender(
+		t,
+		database.TargetTypeHTTP,
+		`{"url":"https://example.com/hook/abc"}`,
+		payload,
+	)
+
+	assert.NotContains(t, body, payload)
+	assert.NotContains(t, body, "<script>alert")
+	assert.Contains(t, body, "alert")
+}
+
+// TestHandleSourceLogs_RedactsCredentialEchoedInResponse
+// covers the case that makes rendering a response body a
+// disclosure question at all: the remote echoes back the
+// credential the request carried, and the page would then put
+// it on the operator's screen.
+func TestHandleSourceLogs_RedactsCredentialEchoedInResponse(
+	t *testing.T,
+) {
+	t.Parallel()
+
+	body := seedFailureAndRender(
+		t,
+		database.TargetTypeSlack,
+		`{"webhookUrl":"`+slackWebhookURL+`"}`,
+		"no_service: "+slackWebhookURL,
+	)
+
+	assert.NotContains(t, body, slackSecretPath)
+	assert.NotContains(t, body, "T00000000")
+	assert.NotContains(t, body, "B00000000")
+	assert.Contains(t, body, delivery.RedactionMarker)
+
+	// The rest of the response is still shown, or the
+	// redaction would have cost the operator the diagnosis.
+	assert.Contains(t, body, "no_service")
+}
+
+// TestHandleSourceLogs_RedactsCredentialEchoedInError covers
+// the same disclosure through the error field. The delivery
+// engine masks the URL out of the errors it stores, so this
+// holds the read path to the rows written before it did.
+func TestHandleSourceLogs_RedactsCredentialEchoedInError(
+	t *testing.T,
+) {
+	t.Parallel()
+
+	var (
+		h     *handlers.Handlers
+		sess  *session.Session
+		db    *database.Database
+		dbMgr *database.WebhookDBManager
+	)
+
+	app := newTestApp(t, &h, &sess, &db, &dbMgr)
+	app.RequireStart()
+
+	t.Cleanup(app.RequireStop)
+
+	wh := seedWebhook(t, db)
+	tgt := seedConfiguredTarget(
+		t, db, wh.ID,
+		database.TargetTypeSlack,
+		`{"webhookUrl":"`+slackWebhookURL+`"}`,
+	)
+
+	dlv := seedFailedDelivery(t, dbMgr, wh.ID, tgt.ID, "")
+
+	webhookDB, err := dbMgr.GetDB(wh.ID)
+	require.NoError(t, err)
+
+	// An unmasked transport error, exactly as Go's HTTP
+	// client renders one.
+	require.NoError(t, webhookDB.Model(
+		&database.DeliveryResult{},
+	).Where(
+		"delivery_id = ?", dlv.ID,
+	).Update(
+		"error",
+		`Post "`+slackWebhookURL+`": dial tcp: i/o timeout`,
+	).Error)
+
+	body := renderSourceLogsPage(t, h, sess, wh.ID)
+
+	assert.NotContains(t, body, slackSecretPath)
+	assert.Contains(t, body, delivery.RedactionMarker)
+	assert.Contains(t, body, "i/o timeout")
+}
+
+// severedPadding is the filler that puts the end of an echoed
+// webhook URL five bytes past a cut at the response cap, so
+// the cut leaves the workspace ID, the bot ID and all but the
+// last few token characters behind.
+func severedPadding() string {
+	const severedTail = 5
+
+	return strings.Repeat(
+		"A", responseCap-len(slackWebhookURL)+severedTail,
+	)
+}
+
+// TestHandleSourceLogs_RedactsCredentialSeveredByTheEngineCut
+// is the regression test for a redactor gated on the SQL cut
+// alone. The delivery engine stops reading a response at its
+// own cap, which is the same number of bytes this page
+// renders, so a row the engine cut is byte-for-byte
+// indistinguishable from a complete response and that gate
+// never opened on anything the engine writes.
+//
+// The seeded body is what the engine stores for any remote
+// that sends at least that much: exactly responseCap bytes,
+// ending in a severed webhook URL.
+// TestDeliverHTTP_CutsStoredResponseAtMaxBodyLog in
+// internal/delivery pins that this is the size it produces.
+func TestHandleSourceLogs_RedactsCredentialSeveredByTheEngineCut(
+	t *testing.T,
+) {
+	t.Parallel()
+
+	sent := severedPadding() + slackWebhookURL +
+		strings.Repeat("Z", 128)
+	stored := sent[:responseCap]
+
+	require.Len(
+		t, stored, responseCap,
+		"the engine stores exactly the cap, never more",
+	)
+	require.Contains(
+		t, stored, "T00000000",
+		"the severed credential must be in what is seeded",
+	)
+
+	body := seedFailureAndRender(
+		t,
+		database.TargetTypeSlack,
+		`{"webhookUrl":"`+slackWebhookURL+`"}`,
+		stored,
+	)
+
+	assert.NotContains(t, body, "T00000000")
+	assert.NotContains(t, body, "B00000000")
+	assert.Contains(t, body, delivery.RedactionMarker)
+	assert.Contains(
+		t, body, "reached the recording limit",
+		"a body the engine cut must not be shown as complete",
+	)
+}
+
+// TestHandleSourceLogs_RedactsCredentialSeveredBySQLCut covers
+// the same severing for a row larger than the cap, which is
+// SQLite's cut rather than the engine's. The current engine
+// writes no such row; rows predating its cap or restored from
+// an archive are not bounded by it, which is why the page cuts
+// again in SQL and has to redact that cut too.
+func TestHandleSourceLogs_RedactsCredentialSeveredBySQLCut(
+	t *testing.T,
+) {
+	t.Parallel()
+
+	stored := severedPadding() + slackWebhookURL +
+		strings.Repeat("Z", 128)
+
+	require.Greater(
+		t, len(stored), responseCap,
+		"the stored body must exceed the cap or nothing is cut",
+	)
+
+	body := seedFailureAndRender(
+		t,
+		database.TargetTypeSlack,
+		`{"webhookUrl":"`+slackWebhookURL+`"}`,
+		stored,
+	)
+
+	assert.NotContains(t, body, "T00000000")
+	assert.NotContains(t, body, "B00000000")
+	assert.NotContains(
+		t, body, slackWebhookURL[:len(slackWebhookURL)-10],
+	)
+	assert.Contains(t, body, delivery.RedactionMarker)
+}
+
+// TestHandleSourceLogs_RedactsForSoftDeletedTarget covers a
+// target an operator has deleted. The row is only soft deleted
+// and its deliveries survive in the per-webhook database, so
+// its redactor has to survive with it or every response body
+// it ever recorded renders unredacted.
+func TestHandleSourceLogs_RedactsForSoftDeletedTarget(
+	t *testing.T,
+) {
+	t.Parallel()
+
+	var (
+		h     *handlers.Handlers
+		sess  *session.Session
+		db    *database.Database
+		dbMgr *database.WebhookDBManager
+	)
+
+	app := newTestApp(t, &h, &sess, &db, &dbMgr)
+	app.RequireStart()
+
+	t.Cleanup(app.RequireStop)
+
+	wh := seedWebhook(t, db)
+	tgt := seedConfiguredTarget(
+		t, db, wh.ID,
+		database.TargetTypeSlack,
+		`{"webhookUrl":"`+slackWebhookURL+`"}`,
+	)
+
+	seedFailedDelivery(
+		t, dbMgr, wh.ID, tgt.ID,
+		"no_service: "+slackWebhookURL,
+	)
+
+	require.NoError(t, db.DB().Delete(tgt).Error)
+
+	body := renderSourceLogsPage(t, h, sess, wh.ID)
+
+	assert.NotContains(t, body, slackSecretPath)
+	assert.NotContains(t, body, "T00000000")
+	assert.Contains(t, body, delivery.RedactionMarker)
+	assert.Contains(t, body, "no_service")
+}
+
+// TestHandleSourceLogs_BoundsRenderedAttempts pins the ceiling
+// on how many of one delivery's attempts reach the page, and
+// that what it drops is counted rather than hidden.
+func TestHandleSourceLogs_BoundsRenderedAttempts(t *testing.T) {
+	t.Parallel()
+
+	const extraAttempts = 7
+
+	var (
+		h     *handlers.Handlers
+		sess  *session.Session
+		db    *database.Database
+		dbMgr *database.WebhookDBManager
+	)
+
+	app := newTestApp(t, &h, &sess, &db, &dbMgr)
+	app.RequireStart()
+
+	t.Cleanup(app.RequireStop)
+
+	wh := seedWebhook(t, db)
+	tgt := seedConfiguredTarget(
+		t, db, wh.ID, database.TargetTypeLog, "",
+	)
+
+	dlv := seedFailedDelivery(t, dbMgr, wh.ID, tgt.ID, "")
+
+	webhookDB, err := dbMgr.GetDB(wh.ID)
+	require.NoError(t, err)
+
+	total := handlers.MaxRenderedAttemptsForTest + extraAttempts
+
+	// seedFailedDelivery already recorded one attempt.
+	for i := range total - 1 {
+		require.NoError(t, webhookDB.Omit(
+			clause.Associations,
+		).Create(&database.DeliveryResult{
+			DeliveryID: dlv.ID,
+			AttemptNum: attemptNumber + 1 + i,
+			Error:      attemptError,
+		}).Error)
+	}
+
+	views := h.LoadEventLogViewsForTest(
+		httptest.NewRecorder(), *wh, 1,
+	)
+	require.Len(t, views, 1)
+	require.Len(t, views[0].Deliveries, 1)
+
+	dv := views[0].Deliveries[0]
+
+	assert.Equal(t, total, dv.AttemptCount)
+	assert.Len(
+		t, dv.Results, handlers.MaxRenderedAttemptsForTest,
+	)
+	assert.Equal(t, extraAttempts, dv.AttemptsOmitted)
+
+	page := renderSourceLogsPage(t, h, sess, wh.ID)
+
+	assert.Contains(t, page, "attempts omitted")
+	assert.Contains(
+		t, page, strconv.Itoa(total)+" attempts",
+		"the header must count every recorded attempt",
+	)
+}
+
+// TestHandleSourceLogs_BoundsOversizeResponse proves the
+// rendered page is bounded by the response cap rather than by
+// the stored response size. The cut happens in SQLite, so the
+// oversized value never becomes a Go string; this asserts the
+// observable consequence, that neither the page nor the
+// projection carries the tail.
+func TestHandleSourceLogs_BoundsOversizeResponse(t *testing.T) {
+	t.Parallel()
+
+	const tail = "QQRESPONSETAILQQ"
+
+	var (
+		h     *handlers.Handlers
+		sess  *session.Session
+		db    *database.Database
+		dbMgr *database.WebhookDBManager
+	)
+
+	app := newTestApp(t, &h, &sess, &db, &dbMgr)
+	app.RequireStart()
+
+	t.Cleanup(app.RequireStop)
+
+	wh := seedWebhook(t, db)
+	tgt := seedConfiguredTarget(
+		t, db, wh.ID, database.TargetTypeLog, "",
+	)
+
+	stored := strings.Repeat("A", responseCap*4) + tail
+	seedFailedDelivery(t, dbMgr, wh.ID, tgt.ID, stored)
+
+	views := h.LoadEventLogViewsForTest(
+		httptest.NewRecorder(), *wh, 1,
+	)
+	require.Len(t, views, 1)
+	require.Len(t, views[0].Deliveries, 1)
+	require.Len(t, views[0].Deliveries[0].Results, 1)
+
+	attempt := views[0].Deliveries[0].Results[0]
+
+	assert.LessOrEqual(
+		t, len(attempt.ResponseBody), responseCap,
+	)
+	assert.Equal(
+		t, int64(len(stored)), attempt.ResponseBytes,
+	)
+	assert.True(t, attempt.ResponseTruncated)
+
+	page := renderSourceLogsPage(t, h, sess, wh.ID)
+
+	assert.NotContains(t, page, tail)
+	assert.Contains(
+		t, page, "Response truncated for display",
+	)
+}

internal/handlers/export_test.go

@@ -19,6 +19,14 @@ func (s *Handlers) SetLogForTest(log *slog.Logger) {
 // to the handlers_test package.
 const MaxRenderedBodyBytesForTest = maxRenderedBodyBytes
 
+// MaxRenderedResponseBytesForTest exposes the event log's
+// delivery response cap to the handlers_test package.
+const MaxRenderedResponseBytesForTest = maxRenderedResponseBytes
+
+// MaxRenderedAttemptsForTest exposes the event log's
+// per-delivery attempt ceiling to the handlers_test package.
+const MaxRenderedAttemptsForTest = maxRenderedAttempts
+
 // DummyVerificationsForTest reports how many equivalent-cost
 // verifications were charged for usernames that do not exist. It
 // lets a test prove the anti-enumeration path ran without timing
@@ -43,7 +51,9 @@ func (s *Handlers) LoadEventLogViewsForTest(
 	webhook database.Webhook,
 	page int,
 ) []EventLogView {
-	views, _ := s.loadEventsWithDeliveries(w, webhook, nil, page)
+	views, _, _ := s.loadEventsWithDeliveries(
+		w, webhook, nil, page,
+	)
 
 	return views
 }
@@ -69,18 +79,29 @@ func (s *Handlers) RenderTemplateForTest(
 	s.renderTemplate(w, r, pageTemplate, data)
 }
 
-// BuildSlackTargetConfigForTest exposes buildURLTargetConfig
-// with the Slack target parameters for use in the
-// handlers_test package.
+// BuildSlackTargetConfigForTest exposes
+// buildSlackTargetConfig for use in the handlers_test package.
 func (s *Handlers) BuildSlackTargetConfigForTest(
 	w http.ResponseWriter,
 	r *http.Request,
 	targetURL string,
 ) (string, error) {
-	return s.buildURLTargetConfig(
-		w, r, targetURL, "webhookUrl",
-		"Webhook URL is required for Slack targets",
-	)
+	return s.buildSlackTargetConfig(w, r, targetURL)
+}
+
+// BuildHTTPTargetConfigForTest exposes buildHTTPTargetConfig
+// for use in the handlers_test package, taking the form fields
+// an HTTP target's configuration is built from.
+func (s *Handlers) BuildHTTPTargetConfigForTest(
+	w http.ResponseWriter,
+	r *http.Request,
+	targetURL, headers, timeout string,
+) (string, error) {
+	return s.buildHTTPTargetConfig(w, r, targetFormInput{
+		URL:     targetURL,
+		Headers: headers,
+		Timeout: timeout,
+	})
 }
 
 // BuildDatabaseTargetConfigForTest exposes

internal/handlers/handlers.go

@@ -18,6 +18,7 @@ import (
 	"sneak.berlin/go/webhooker/internal/globals"
 	"sneak.berlin/go/webhooker/internal/healthcheck"
 	"sneak.berlin/go/webhooker/internal/logger"
+	"sneak.berlin/go/webhooker/internal/metrics"
 	"sneak.berlin/go/webhooker/internal/middleware"
 	"sneak.berlin/go/webhooker/internal/session"
 	"sneak.berlin/go/webhooker/templates"
@@ -73,6 +74,7 @@ type Handlers struct {
 	mw        *middleware.Middleware
 	notifier  delivery.Notifier
 	evictor   delivery.WebhookEvictor
+	mtr       *metrics.Set
 	templates map[string]*template.Template
 
 	// dummyVerifications counts the equivalent-cost verifications
@@ -114,6 +116,7 @@ func New(
 	s.mw = params.Middleware
 	s.notifier = params.Notifier
 	s.evictor = params.Evictor
+	s.mtr = metrics.Default()
 
 	// Parse all page templates once at startup
 	s.templates = map[string]*template.Template{
@@ -124,6 +127,7 @@ func New(
 		"source_detail.html": parsePageTemplate("source_detail.html"),
 		"source_edit.html":   parsePageTemplate("source_edit.html"),
 		"source_logs.html":   parsePageTemplate("source_logs.html"),
+		"target_edit.html":   parsePageTemplate("target_edit.html"),
 	}
 
 	lc.Append(fx.Hook{

internal/handlers/source_management.go

@@ -4,11 +4,13 @@ import (
 	"encoding/json"
 	"errors"
 	"net/http"
+	"slices"
 	"strconv"
 	"strings"
 
 	"github.com/go-chi/chi"
 	"github.com/google/uuid"
+	"gorm.io/gorm"
 	"sneak.berlin/go/webhooker/internal/database"
 	"sneak.berlin/go/webhooker/internal/delivery"
 )
@@ -100,6 +102,32 @@ type DeliveryView struct {
 	ID     string
 	Status database.DeliveryStatus
 	Target delivery.TargetView
+
+	// Results is this delivery's attempts in attempt order,
+	// bounded by maxRenderedAttempts. Without them a failure
+	// renders as the status word alone and says nothing about
+	// why.
+	Results []DeliveryResultView
+
+	// AttemptCount is how many attempts were recorded, which
+	// is more than len(Results) once the middle was dropped.
+	AttemptCount int
+
+	// AttemptsOmitted is how many attempts were dropped from
+	// the middle of Results. The page must show it, or the
+	// bound would hide history rather than fold it.
+	AttemptsOmitted int
+}
+
+// eventLogTarget is what the event log needs to know about
+// one target: the display-safe view its template renders, and
+// the redactor that keeps that target's own credential out of
+// the text its remote peer chose. The two are kept together
+// so a caller cannot pick up one without the other, and apart
+// from TargetView so the secrets never reach a template.
+type eventLogTarget struct {
+	View     delivery.TargetView
+	Redactor delivery.Redactor
 }
 
 // HandleSourceList shows a list of user's webhooks.
@@ -765,12 +793,24 @@ func (h *Handlers) HandleSourceLogs() http.HandlerFunc {
 			return
 		}
 
-		targets := h.loadTargetMap(webhook.ID)
+		targets, err := h.loadTargetMap(webhook.ID)
+		if err != nil {
+			// Without the map every delivery renders through a
+			// zero redactor, so failing the page is the only
+			// safe answer.
+			h.serverError(w, "failed to load targets", err)
+
+			return
+		}
+
 		page := h.parsePage(r)
 
-		evts, total := h.loadEventsWithDeliveries(
+		evts, total, ok := h.loadEventsWithDeliveries(
 			w, webhook, targets, page,
 		)
+		if !ok {
+			return
+		}
 
 		totalPages := int(total) / paginationPerPage
 		if int(total)%paginationPerPage != 0 {
@@ -794,29 +834,54 @@ func (h *Handlers) HandleSourceLogs() http.HandlerFunc {
 }
 
 // loadTargetMap loads targets into a map of display-safe
-// views keyed by target ID. The projection happens here so
-// that no caller can hand a raw target, configuration blob
-// and all, to a template.
+// views keyed by target ID, each paired with its redactor.
+// The projection happens here so that no caller can hand a
+// raw target, configuration blob and all, to a template: the
+// raw rows do not leave this function.
+//
+// The load is Unscoped because deleting a target only soft
+// deletes the row while its deliveries survive in the
+// per-webhook database: a scoped load leaves those deliveries
+// with a zero redactor, which renders their response bodies
+// unredacted. Only the redactor half of the map is built from
+// deleted rows. The view half, which is what the page lists,
+// stays scoped.
 func (h *Handlers) loadTargetMap(
 	webhookID string,
-) map[string]delivery.TargetView {
+) (map[string]eventLogTarget, error) {
 	var targets []database.Target
 
-	h.db.DB().Where(
+	err := h.db.DB().Unscoped().Where(
 		"webhook_id = ?", webhookID,
-	).Find(&targets)
-
-	views := delivery.NewTargetViews(targets)
-
-	targetMap := make(
-		map[string]delivery.TargetView, len(views),
-	)
-
-	for _, v := range views {
-		targetMap[v.ID] = v
+	).Find(&targets).Error
+	if err != nil {
+		return nil, err
 	}
 
-	return targetMap
+	targetMap := make(
+		map[string]eventLogTarget, len(targets),
+	)
+	live := make([]database.Target, 0, len(targets))
+
+	for i := range targets {
+		targetMap[targets[i].ID] = eventLogTarget{
+			Redactor: delivery.NewRedactor(&targets[i]),
+		}
+
+		if !targets[i].DeletedAt.Valid {
+			live = append(live, targets[i])
+		}
+	}
+
+	// The views come from NewTargetViews rather than being
+	// rebuilt here, so the masking rules stay in one place.
+	for _, v := range delivery.NewTargetViews(live) {
+		entry := targetMap[v.ID]
+		entry.View = v
+		targetMap[v.ID] = entry
+	}
+
+	return targetMap, nil
 }
 
 // parsePage extracts a page number from the query string.
@@ -837,18 +902,22 @@ func (h *Handlers) parsePage(r *http.Request) int {
 // deliveries from the per-webhook database. Events come back
 // as capped projections rather than database.Event rows: see
 // eventLogColumns for why the cut happens in SQL.
+//
+// The bool reports whether the load succeeded. It is false
+// once this has answered the request with an error, and the
+// caller must then render nothing further.
 func (h *Handlers) loadEventsWithDeliveries(
 	w http.ResponseWriter,
 	webhook database.Webhook,
-	targetMap map[string]delivery.TargetView,
+	targetMap map[string]eventLogTarget,
 	page int,
-) ([]EventLogView, int64) {
+) ([]EventLogView, int64, bool) {
 	var totalEvents int64
 
 	var result []EventLogView
 
 	if !h.dbMgr.DBExists(webhook.ID) {
-		return result, totalEvents
+		return result, totalEvents, true
 	}
 
 	webhookDB, err := h.dbMgr.GetDB(webhook.ID)
@@ -857,7 +926,7 @@ func (h *Handlers) loadEventsWithDeliveries(
 			w, "failed to get webhook database", err,
 		)
 
-		return nil, 0
+		return nil, 0, false
 	}
 
 	webhookDB.Model(&database.Event{}).Where(
@@ -877,43 +946,170 @@ func (h *Handlers) loadEventsWithDeliveries(
 	).Find(&rows)
 
 	result = make([]EventLogView, len(rows))
+	eventDeliveries := make([][]database.Delivery, len(rows))
+
+	var deliveryIDs []string
 
 	for i := range rows {
 		result[i] = rows[i].view()
 
-		var deliveries []database.Delivery
-
 		webhookDB.Where(
 			"event_id = ?", rows[i].ID,
-		).Find(&deliveries)
+		).Find(&eventDeliveries[i])
 
+		for j := range eventDeliveries[i] {
+			deliveryIDs = append(
+				deliveryIDs, eventDeliveries[i][j].ID,
+			)
+		}
+	}
+
+	attempts, err := h.loadDeliveryResults(
+		webhookDB, deliveryIDs,
+	)
+	if err != nil {
+		h.serverError(
+			w, "failed to load delivery attempts", err,
+		)
+
+		return nil, 0, false
+	}
+
+	for i := range rows {
 		result[i].Deliveries = newDeliveryViews(
-			deliveries, targetMap,
+			eventDeliveries[i], targetMap, attempts,
 		)
 	}
 
-	return result, totalEvents
+	return result, totalEvents, true
+}
+
+// deliveryIDChunkSize bounds how many delivery IDs go into one
+// IN clause. SQLite refuses a statement carrying more than
+// SQLITE_MAX_VARIABLE_NUMBER (32766) bound parameters, and a
+// page holds one delivery per target per event, so a webhook
+// with enough targets would turn the whole query into an error
+// and the page into zero attempts.
+const deliveryIDChunkSize = 500
+
+// loadDeliveryResults loads the recorded attempts for the
+// page's deliveries, keyed by delivery ID.
+//
+// Each response body is cut by SQLite rather than in Go, for
+// the reason deliveryResultColumns gives. How many attempts a
+// delivery has is the target's MaxRetries, which the
+// authenticated operator sets; how many of them reach the page
+// is bounded again by maxRenderedAttempts.
+func (h *Handlers) loadDeliveryResults(
+	webhookDB *gorm.DB,
+	deliveryIDs []string,
+) (map[string][]deliveryResultRow, error) {
+	byDelivery := make(map[string][]deliveryResultRow)
+
+	for chunk := range slices.Chunk(
+		deliveryIDs, deliveryIDChunkSize,
+	) {
+		var rows []deliveryResultRow
+
+		err := webhookDB.Model(
+			&database.DeliveryResult{},
+		).Select(
+			deliveryResultColumns, maxRenderedResponseBytes,
+		).Where(
+			"delivery_id IN ?", chunk,
+		).Order("attempt_num ASC").Find(&rows).Error
+		if err != nil {
+			// Returning what was loaded so far renders the
+			// deliveries in the failed chunk as never having run,
+			// which is indistinguishable from ones that really
+			// never ran. The page fails instead.
+			return nil, err
+		}
+
+		for i := range rows {
+			byDelivery[rows[i].DeliveryID] = append(
+				byDelivery[rows[i].DeliveryID], rows[i],
+			)
+		}
+	}
+
+	return byDelivery, nil
 }
 
 // newDeliveryViews projects deliveries for rendering,
-// resolving each one's target to its display-safe view.
+// resolving each one's target to its display-safe view and
+// each one's attempts through that target's redactor.
 func newDeliveryViews(
 	deliveries []database.Delivery,
-	targetMap map[string]delivery.TargetView,
+	targetMap map[string]eventLogTarget,
+	attempts map[string][]deliveryResultRow,
 ) []DeliveryView {
 	views := make([]DeliveryView, len(deliveries))
 
 	for i := range deliveries {
+		target := targetMap[deliveries[i].TargetID]
+		rows := attempts[deliveries[i].ID]
+
+		results, omitted := renderedAttempts(
+			rows, target.Redactor,
+		)
+
 		views[i] = DeliveryView{
-			ID:     deliveries[i].ID,
-			Status: deliveries[i].Status,
-			Target: targetMap[deliveries[i].TargetID],
+			ID:              deliveries[i].ID,
+			Status:          deliveries[i].Status,
+			Target:          target.View,
+			Results:         results,
+			AttemptCount:    len(rows),
+			AttemptsOmitted: omitted,
 		}
 	}
 
 	return views
 }
 
+// maxRenderedAttempts bounds how many of one delivery's
+// attempts the page renders. Past it the middle is dropped and
+// counted, keeping the first attempts and the last ones: how
+// the delivery started failing and how it ended are what a
+// reader needs, and the count says plainly that the rest was
+// dropped rather than never recorded.
+const (
+	renderedAttemptsHead = 10
+	renderedAttemptsTail = 10
+	maxRenderedAttempts  = renderedAttemptsHead +
+		renderedAttemptsTail
+)
+
+// renderedAttempts projects a delivery's attempts through the
+// target's redactor, at most maxRenderedAttempts of them, and
+// reports how many it dropped.
+func renderedAttempts(
+	rows []deliveryResultRow,
+	redactor delivery.Redactor,
+) ([]DeliveryResultView, int) {
+	omitted := 0
+
+	if len(rows) > maxRenderedAttempts {
+		omitted = len(rows) - maxRenderedAttempts
+
+		kept := make(
+			[]deliveryResultRow, 0, maxRenderedAttempts,
+		)
+		kept = append(kept, rows[:renderedAttemptsHead]...)
+		kept = append(
+			kept, rows[len(rows)-renderedAttemptsTail:]...,
+		)
+		rows = kept
+	}
+
+	views := make([]DeliveryResultView, len(rows))
+	for i := range rows {
+		views[i] = rows[i].view(redactor)
+	}
+
+	return views, omitted
+}
+
 // HandleEntrypointCreate handles adding a new entrypoint.
 func (h *Handlers) HandleEntrypointCreate() http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
@@ -1029,9 +1225,7 @@ func (h *Handlers) processTargetCreate(
 	// Referer headers and error trackers record.
 	name := r.PostFormValue("name")
 	targetType := database.TargetType(r.PostFormValue("type"))
-	targetURL := r.PostFormValue("url")
 	maxRetriesStr := r.PostFormValue("max_retries")
-	expiry := r.PostFormValue("expiry")
 
 	if name == "" {
 		http.Error(
@@ -1051,7 +1245,7 @@ func (h *Handlers) processTargetCreate(
 	}
 
 	configJSON, err := h.buildTargetConfig(
-		w, r, targetType, targetURL, expiry,
+		w, r, targetType, targetFormInputFrom(r),
 	)
 	if err != nil {
 		return
@@ -1108,28 +1302,60 @@ func parseNonNegativeInt(s string) int {
 	return 0
 }
 
-// buildTargetConfig builds the JSON config string for a target.
-// The expiry form value is read by the caller (which bounds the
-// request body) and applies to database targets only.
+// targetFormInput carries the raw form values describing a target's
+// configuration. Both the create and the edit path fill one and hand
+// it to buildTargetConfig, so neither can come to validate a
+// destination differently from the other.
+type targetFormInput struct {
+	// URL is the destination for an HTTP target and the webhook URL
+	// for a Slack target.
+	URL string
+	// Headers is an HTTP target's headers, one "Name: value" per
+	// line.
+	Headers string
+	// Timeout is an HTTP target's per-request timeout in seconds.
+	Timeout string
+	// Expiry is a database (archive) target's row expiry.
+	Expiry string
+}
+
+// targetFormInputFrom reads the configuration fields from a request
+// body. The body size cap is enforced by the MaxBodySize middleware,
+// which runs before CSRF parses the form.
+//
+// Every field is read with PostFormValue, not FormValue. FormValue
+// falls back to the query string, which would let
+// `POST /source/{id}/targets?url=https://hooks.slack.com/...`
+// configure a target from a value the request line carries — and the
+// request line, unlike the body, is what logs, proxies, Referer
+// headers and error trackers record. The headers field is under the
+// same rule and for the same reason: its values are authorization
+// tokens.
+func targetFormInputFrom(r *http.Request) targetFormInput {
+	return targetFormInput{
+		URL:     r.PostFormValue("url"),
+		Headers: r.PostFormValue("headers"),
+		Timeout: r.PostFormValue("timeout"),
+		Expiry:  r.PostFormValue("expiry"),
+	}
+}
+
+// buildTargetConfig builds the JSON config string for a target from
+// the submitted form values, writing its own 4xx response on
+// rejection. Which fields of in apply depends on the target type.
 func (h *Handlers) buildTargetConfig(
 	w http.ResponseWriter,
 	r *http.Request,
 	targetType database.TargetType,
-	targetURL, expiry string,
+	in targetFormInput,
 ) (string, error) {
 	switch targetType {
 	case database.TargetTypeHTTP:
-		return h.buildURLTargetConfig(
-			w, r, targetURL, "url",
-			"URL is required for HTTP targets",
-		)
+		return h.buildHTTPTargetConfig(w, r, in)
 	case database.TargetTypeSlack:
-		return h.buildURLTargetConfig(
-			w, r, targetURL, "webhookUrl",
-			"Webhook URL is required for Slack targets",
-		)
+		return h.buildSlackTargetConfig(w, r, in.URL)
 	case database.TargetTypeDatabase:
-		return h.buildDatabaseTargetConfig(w, expiry)
+		return h.buildDatabaseTargetConfig(w, in.Expiry)
 	case database.TargetTypeLog:
 		return "", nil
 	default:
@@ -1142,14 +1368,83 @@ func (h *Handlers) buildTargetConfig(
 	}
 }
 
-// buildURLTargetConfig builds config JSON for a target whose
-// configuration is a single SSRF-validated URL stored under
-// configKey. missingMsg is the error shown when no URL is given.
-func (h *Handlers) buildURLTargetConfig(
+// buildHTTPTargetConfig builds config JSON for an HTTP target: an
+// SSRF-validated destination plus the optional headers and timeout
+// the delivery path honours.
+func (h *Handlers) buildHTTPTargetConfig(
 	w http.ResponseWriter,
 	r *http.Request,
-	targetURL, configKey, missingMsg string,
+	in targetFormInput,
 ) (string, error) {
+	err := h.validateTargetURL(
+		w, r, in.URL, "URL is required for HTTP targets",
+	)
+	if err != nil {
+		return "", err
+	}
+
+	headers, err := delivery.ParseTargetHeaders(in.Headers)
+	if err != nil {
+		http.Error(
+			w,
+			"Invalid headers: "+err.Error(),
+			http.StatusBadRequest,
+		)
+
+		return "", err
+	}
+
+	timeout, err := delivery.ParseTargetTimeout(in.Timeout)
+	if err != nil {
+		http.Error(
+			w,
+			"Invalid timeout: "+err.Error(),
+			http.StatusBadRequest,
+		)
+
+		return "", err
+	}
+
+	return marshalTargetConfig(w, delivery.HTTPTargetConfig{
+		URL:     in.URL,
+		Headers: headers,
+		Timeout: timeout,
+	})
+}
+
+// buildSlackTargetConfig builds config JSON for a Slack target,
+// whose whole configuration is one SSRF-validated webhook URL.
+func (h *Handlers) buildSlackTargetConfig(
+	w http.ResponseWriter,
+	r *http.Request,
+	targetURL string,
+) (string, error) {
+	err := h.validateTargetURL(
+		w, r, targetURL,
+		"Webhook URL is required for Slack targets",
+	)
+	if err != nil {
+		return "", err
+	}
+
+	return marshalTargetConfig(w, delivery.SlackTargetConfig{
+		WebhookURL: targetURL,
+	})
+}
+
+// validateTargetURL rejects an empty or SSRF-blocked destination,
+// writing the 400 itself. missingMsg is the error shown when no URL
+// is given.
+//
+// It is the single point at which a user-supplied destination enters
+// the SSRF guard, on create and on edit alike. An edit path that
+// reached storage without passing through here would reopen the hole
+// the guard closes.
+func (h *Handlers) validateTargetURL(
+	w http.ResponseWriter,
+	r *http.Request,
+	targetURL, missingMsg string,
+) error {
 	if targetURL == "" {
 		http.Error(
 			w,
@@ -1157,7 +1452,7 @@ func (h *Handlers) buildURLTargetConfig(
 			http.StatusBadRequest,
 		)
 
-		return "", errMissingURL
+		return errMissingURL
 	}
 
 	err := delivery.ValidateTargetURL(
@@ -1178,11 +1473,18 @@ func (h *Handlers) buildURLTargetConfig(
 			http.StatusBadRequest,
 		)
 
-		return "", err
+		return err
 	}
 
-	cfg := map[string]any{configKey: targetURL}
+	return nil
+}
 
+// marshalTargetConfig serialises a target configuration for storage,
+// writing a 500 itself if it cannot.
+func marshalTargetConfig(
+	w http.ResponseWriter,
+	cfg any,
+) (string, error) {
 	configBytes, err := json.Marshal(cfg)
 	if err != nil {
 		http.Error(
@@ -1222,19 +1524,9 @@ func (h *Handlers) buildDatabaseTargetConfig(
 		return "", err
 	}
 
-	cfg := map[string]any{"expiry": expiry}
-
-	configBytes, err := json.Marshal(cfg)
-	if err != nil {
-		http.Error(
-			w, "Internal server error",
-			http.StatusInternalServerError,
-		)
-
-		return "", err
-	}
-
-	return string(configBytes), nil
+	return marshalTargetConfig(
+		w, map[string]any{"expiry": expiry},
+	)
 }
 
 // HandleEntrypointDelete handles deleting an entrypoint.

internal/handlers/target_edit.go

@@ -0,0 +1,221 @@
+package handlers
+
+import (
+	"net/http"
+
+	"github.com/go-chi/chi"
+	"sneak.berlin/go/webhooker/internal/database"
+	"sneak.berlin/go/webhooker/internal/delivery"
+)
+
+// targetEditTemplate is the page the target edit form renders.
+const targetEditTemplate = "target_edit.html"
+
+// tmplKeyTarget is the template data key for the target being
+// edited, and tmplKeyMaxTimeout for the timeout ceiling the form
+// tells the user about.
+const (
+	tmplKeyTarget     = "Target"
+	tmplKeyMaxTimeout = "MaxTimeout"
+)
+
+// configUnreadableMessage is shown when a target's stored
+// configuration does not parse. It says plainly that saving replaces
+// the stored value rather than preserving it, because the form
+// cannot pre-fill what it could not read.
+const configUnreadableMessage = "The stored configuration for this " +
+	"target could not be read. Enter the values below; saving " +
+	"replaces the stored configuration."
+
+// targetEditView is the display model for the target edit page.
+//
+// It carries the target's row fields alongside its UNMASKED
+// configuration, and deliberately omits database.Target's raw
+// Config blob: the form renders named fields, and giving the
+// template the blob as well would put an unreviewed second path to
+// the credential on the page.
+type targetEditView struct {
+	ID         string
+	Name       string
+	Type       database.TargetType
+	Active     bool
+	MaxRetries int
+	Config     delivery.TargetConfigForm
+}
+
+// HandleTargetEdit shows the form to edit a target.
+//
+// This page is the one place the full destination URL and header
+// values are shown. It is reachable only through the
+// /source/{sourceID} route group, which supplies RequireAuth and
+// NoCache, and only for a target of a webhook the session's user
+// owns; masking (delivery.TargetView) is unchanged everywhere else.
+func (h *Handlers) HandleTargetEdit() http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		webhook, target, ok := h.ownedTarget(w, r)
+		if !ok {
+			return
+		}
+
+		cfg, err := delivery.NewTargetConfigForm(target)
+		msg := ""
+
+		if err != nil {
+			// The error carries the parse failure, never the
+			// blob, so it is safe to log against the target id.
+			h.log.Warn(
+				"stored target config could not be read for editing",
+				"target_id", target.ID,
+				"error", err,
+			)
+
+			msg = configUnreadableMessage
+		}
+
+		h.renderTargetEdit(w, r, webhook, target, cfg, msg)
+	}
+}
+
+// HandleTargetEditSubmit handles the target edit form submission.
+func (h *Handlers) HandleTargetEditSubmit() http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		webhook, target, ok := h.ownedTarget(w, r)
+		if !ok {
+			return
+		}
+
+		// The body size cap is enforced by the MaxBodySize
+		// middleware, which runs before CSRF parses the form.
+		err := r.ParseForm()
+		if err != nil {
+			http.Error(
+				w, "Bad request", http.StatusBadRequest,
+			)
+
+			return
+		}
+
+		h.applyTargetEdit(w, r, webhook, target)
+	}
+}
+
+// applyTargetEdit validates and saves target edits.
+//
+// The submitted configuration goes through buildTargetConfig, the
+// same builder the create path uses, so an edited destination is
+// SSRF-validated exactly as a new one is.
+//
+// The target's type is not editable. Each type stores a different
+// configuration shape and its delivery history is recorded against
+// the target row, so changing the type of an existing target is
+// really the creation of a different one. The stored type decides
+// which fields the form offers and which builder runs.
+func (h *Handlers) applyTargetEdit(
+	w http.ResponseWriter,
+	r *http.Request,
+	webhook database.Webhook,
+	target *database.Target,
+) {
+	name := r.PostFormValue("name")
+	if name == "" {
+		http.Error(
+			w, "Name is required", http.StatusBadRequest,
+		)
+
+		return
+	}
+
+	configJSON, err := h.buildTargetConfig(
+		w, r, target.Type, targetFormInputFrom(r),
+	)
+	if err != nil {
+		// buildTargetConfig has already written the response.
+		return
+	}
+
+	target.Name = name
+	target.Config = configJSON
+
+	// Retries are offered only by the forms for target types that
+	// retry, so an absent field means "this form does not edit
+	// retries" rather than "set them to zero". Reading it
+	// unconditionally would silently disable retries on any target
+	// saved from a form that does not render the input.
+	if r.PostForm.Has("max_retries") {
+		target.MaxRetries = parseNonNegativeInt(
+			r.PostFormValue("max_retries"),
+		)
+	}
+
+	err = h.db.DB().Save(target).Error
+	if err != nil {
+		h.serverError(w, "failed to update target", err)
+
+		return
+	}
+
+	http.Redirect(
+		w, r, "/source/"+webhook.ID, http.StatusSeeOther,
+	)
+}
+
+// renderTargetEdit renders the target edit page with an optional
+// error message.
+func (h *Handlers) renderTargetEdit(
+	w http.ResponseWriter,
+	r *http.Request,
+	webhook database.Webhook,
+	target *database.Target,
+	cfg delivery.TargetConfigForm,
+	errMsg string,
+) {
+	// The template calls Webhook methods, which take pointer
+	// receivers; html/template cannot address a value stored in a
+	// map.
+	data := map[string]any{
+		tmplKeyWebhook: &webhook,
+		tmplKeyTarget: targetEditView{
+			ID:         target.ID,
+			Name:       target.Name,
+			Type:       target.Type,
+			Active:     target.Active,
+			MaxRetries: target.MaxRetries,
+			Config:     cfg,
+		},
+		tmplKeyMaxTimeout: delivery.MaxTargetTimeoutSeconds,
+		tmplKeyError:      errMsg,
+	}
+
+	h.renderTemplate(w, r, targetEditTemplate, data)
+}
+
+// ownedTarget resolves the request's sourceID and targetID
+// parameters to a target of a webhook the session's user owns.
+//
+// Ownership is decided by the webhook, and the target is then
+// scoped to that webhook, so a target id belonging to someone
+// else's webhook is a 404 rather than an edit of their target. It
+// reports false once it has written the response.
+func (h *Handlers) ownedTarget(
+	w http.ResponseWriter,
+	r *http.Request,
+) (database.Webhook, *database.Target, bool) {
+	webhook, ok := h.ownedWebhook(w, r)
+	if !ok {
+		return database.Webhook{}, nil, false
+	}
+
+	var target database.Target
+
+	err := h.db.DB().Where(
+		"id = ? AND webhook_id = ?",
+		chi.URLParam(r, "targetID"), webhook.ID,
+	).First(&target).Error
+	if err != nil {
+		http.NotFound(w, r)
+
+		return database.Webhook{}, nil, false
+	}
+
+	return webhook, &target, true
+}

internal/handlers/target_edit_test.go

@@ -0,0 +1,637 @@
+package handlers_test
+
+import (
+	"context"
+	"encoding/json"
+	"net/http"
+	"net/http/httptest"
+	"net/url"
+	"strings"
+	"testing"
+
+	"github.com/go-chi/chi"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"gorm.io/gorm/clause"
+	"sneak.berlin/go/webhooker/internal/database"
+	"sneak.berlin/go/webhooker/internal/delivery"
+)
+
+// The destinations the target edit tests configure. Both are literal
+// public addresses rather than hostnames so the SSRF check resolves
+// nothing: with a hostname, a sandbox without DNS would reject the
+// URL for the wrong reason and a test asserting rejection would pass
+// even with the guard removed.
+const (
+	editOriginalURL = "https://93.184.216.34/hooks/original"
+	editReplacedURL = "https://93.184.216.34/hooks/replaced"
+	// editBlockedURL resolves to loopback, which the SSRF guard
+	// refuses. It is what proves the guard runs on the edit path.
+	editBlockedURL = "http://127.0.0.1/hooks/internal"
+)
+
+// editAuthHeader carries a bearer credential, the case the headers
+// field exists for.
+const (
+	editBearerSecret = "QQEDITSECRETQQ"
+	editAuthHeader   = "Authorization: Bearer " + editBearerSecret
+)
+
+// targetRouter mounts the target create and edit routes on a chi
+// router so the handlers see the URL parameters they read.
+func targetRouter(env *sourceTestEnv) *chi.Mux {
+	router := chi.NewRouter()
+	router.Post(
+		"/source/{sourceID}/targets",
+		env.handlers.HandleTargetCreate(),
+	)
+	router.Get(
+		"/source/{sourceID}/targets/{targetID}/edit",
+		env.handlers.HandleTargetEdit(),
+	)
+	router.Post(
+		"/source/{sourceID}/targets/{targetID}/edit",
+		env.handlers.HandleTargetEditSubmit(),
+	)
+
+	return router
+}
+
+// serveTarget drives one request through the target routes as the
+// authenticated test user.
+func serveTarget(
+	env *sourceTestEnv,
+	method, path string,
+	form url.Values,
+) *httptest.ResponseRecorder {
+	body := ""
+	if form != nil {
+		body = form.Encode()
+	}
+
+	req := httptest.NewRequestWithContext(
+		context.Background(), method, path,
+		strings.NewReader(body),
+	)
+	if form != nil {
+		req.Header.Set(
+			"Content-Type",
+			"application/x-www-form-urlencoded",
+		)
+	}
+
+	for _, c := range env.cookies {
+		req.AddCookie(c)
+	}
+
+	w := httptest.NewRecorder()
+	targetRouter(env).ServeHTTP(w, req)
+
+	return w
+}
+
+// seedHTTPTarget creates a webhook and an HTTP target on it through
+// the real create handler, so every case starts from a target the
+// production path produced rather than a hand-written row.
+//
+// Standing the fx app up is what a handler test mostly costs, and
+// internal/handlers is already the slowest package in the suite, so
+// the tests below share one env per test function and give each case
+// its own webhook rather than its own app.
+func seedHTTPTarget(
+	t *testing.T,
+	env *sourceTestEnv,
+	headers, timeout string,
+) (database.Webhook, database.Target) {
+	t.Helper()
+
+	webhook := seedWebhookWithRetention(t, env.db, 30)
+
+	form := url.Values{}
+	form.Set("name", "original-name")
+	form.Set("type", string(database.TargetTypeHTTP))
+	form.Set("url", editOriginalURL)
+	form.Set("headers", headers)
+	form.Set("timeout", timeout)
+	form.Set("max_retries", "3")
+
+	w := serveTarget(
+		env, http.MethodPost,
+		"/source/"+webhook.ID+"/targets", form,
+	)
+	require.Equal(t, http.StatusSeeOther, w.Code, w.Body.String())
+
+	targets := targetsForWebhook(t, env.db, webhook.ID)
+	require.Len(t, targets, 1)
+
+	return webhook, targets[0]
+}
+
+// storedTarget reloads a target row.
+func storedTarget(
+	t *testing.T,
+	env *sourceTestEnv,
+	targetID string,
+) database.Target {
+	t.Helper()
+
+	var target database.Target
+
+	require.NoError(
+		t,
+		env.db.DB().Where("id = ?", targetID).
+			First(&target).Error,
+	)
+
+	return target
+}
+
+// storedHTTPConfig reloads a target and parses its stored HTTP
+// configuration.
+func storedHTTPConfig(
+	t *testing.T,
+	env *sourceTestEnv,
+	targetID string,
+) delivery.HTTPTargetConfig {
+	t.Helper()
+
+	var cfg delivery.HTTPTargetConfig
+
+	require.NoError(
+		t,
+		json.Unmarshal(
+			[]byte(storedTarget(t, env, targetID).Config), &cfg,
+		),
+	)
+
+	return cfg
+}
+
+// editForm is the fully populated edit submission for an HTTP
+// target.
+func editForm(targetURL, headers, timeout string) url.Values {
+	form := url.Values{}
+	form.Set("name", "edited-name")
+	form.Set("url", targetURL)
+	form.Set("headers", headers)
+	form.Set("timeout", timeout)
+	form.Set("max_retries", "5")
+
+	return form
+}
+
+// submitTargetEdit posts the edit form for a target.
+func submitTargetEdit(
+	env *sourceTestEnv,
+	webhookID, targetID string,
+	form url.Values,
+) *httptest.ResponseRecorder {
+	return serveTarget(
+		env, http.MethodPost,
+		"/source/"+webhookID+"/targets/"+targetID+"/edit",
+		form,
+	)
+}
+
+// TestHandleTargetCreate_Configuration covers the half of the gap
+// that is not about editing at all: HTTPTargetConfig has carried
+// Headers and Timeout, and the delivery path has honoured them, but
+// the create form wrote {"url":...} and nothing else, so a
+// destination needing an Authorization header could not be
+// configured through the UI at all.
+func TestHandleTargetCreate_Configuration(t *testing.T) {
+	t.Parallel()
+
+	env := setupSourceTest(t)
+
+	t.Run("stores headers and timeout", func(t *testing.T) {
+		t.Parallel()
+		assertCreateStoresHeadersAndTimeout(t, env)
+	})
+
+	t.Run("without them keeps a url-only config", func(t *testing.T) {
+		t.Parallel()
+		assertCreateKeepsURLOnlyConfig(t, env)
+	})
+}
+
+func assertCreateStoresHeadersAndTimeout(
+	t *testing.T, env *sourceTestEnv,
+) {
+	t.Helper()
+
+	_, target := seedHTTPTarget(
+		t, env, editAuthHeader+"\nX-Tenant: acme\n", "12",
+	)
+
+	cfg := storedHTTPConfig(t, env, target.ID)
+
+	assert.Equal(t, editOriginalURL, cfg.URL)
+	assert.Equal(t, 12, cfg.Timeout)
+	assert.Equal(
+		t,
+		map[string]string{
+			"Authorization": "Bearer " + editBearerSecret,
+			"X-Tenant":      "acme",
+		},
+		cfg.Headers,
+	)
+}
+
+// Without the new fields the stored shape must be the same
+// {"url":...} the create form wrote before they existed, so no
+// existing target's configuration is rewritten by this change.
+func assertCreateKeepsURLOnlyConfig(
+	t *testing.T, env *sourceTestEnv,
+) {
+	t.Helper()
+
+	_, target := seedHTTPTarget(t, env, "", "")
+
+	assert.JSONEq(
+		t, `{"url":"`+editOriginalURL+`"}`, target.Config,
+	)
+}
+
+// TestHandleTargetEditSubmit_Saves is the round trip the issue asks
+// for: create a target, edit it, and confirm the stored config
+// changed.
+func TestHandleTargetEditSubmit_Saves(t *testing.T) {
+	t.Parallel()
+
+	env := setupSourceTest(t)
+
+	t.Run("changes the destination URL", func(t *testing.T) {
+		t.Parallel()
+		assertEditChangesDestination(t, env)
+	})
+
+	t.Run("round trips headers and timeout", func(t *testing.T) {
+		t.Parallel()
+		assertEditRoundTripsHeadersAndTimeout(t, env)
+	})
+
+	t.Run("clearing them removes them", func(t *testing.T) {
+		t.Parallel()
+		assertEditClearingRemovesThem(t, env)
+	})
+
+	t.Run("absent max_retries is not zeroed", func(t *testing.T) {
+		t.Parallel()
+		assertEditKeepsAbsentMaxRetries(t, env)
+	})
+}
+
+func assertEditChangesDestination(
+	t *testing.T, env *sourceTestEnv,
+) {
+	t.Helper()
+
+	webhook, target := seedHTTPTarget(t, env, "", "")
+
+	w := submitTargetEdit(
+		env, webhook.ID, target.ID,
+		editForm(editReplacedURL, "", ""),
+	)
+	require.Equal(t, http.StatusSeeOther, w.Code, w.Body.String())
+
+	assert.Equal(
+		t,
+		editReplacedURL,
+		storedHTTPConfig(t, env, target.ID).URL,
+	)
+
+	reloaded := storedTarget(t, env, target.ID)
+	assert.Equal(t, "edited-name", reloaded.Name)
+	assert.Equal(t, 5, reloaded.MaxRetries)
+	assert.Equal(
+		t, database.TargetTypeHTTP, reloaded.Type,
+		"the edit form must not change a target's type",
+	)
+}
+
+// The two previously unreachable fields must survive create,
+// pre-fill and save.
+func assertEditRoundTripsHeadersAndTimeout(
+	t *testing.T, env *sourceTestEnv,
+) {
+	t.Helper()
+
+	webhook, target := seedHTTPTarget(t, env, editAuthHeader, "7")
+
+	w := submitTargetEdit(
+		env, webhook.ID, target.ID,
+		editForm(
+			editOriginalURL,
+			"Authorization: Bearer rotated\nX-Trace: on",
+			"21",
+		),
+	)
+	require.Equal(t, http.StatusSeeOther, w.Code, w.Body.String())
+
+	cfg := storedHTTPConfig(t, env, target.ID)
+
+	assert.Equal(t, 21, cfg.Timeout)
+	assert.Equal(
+		t,
+		map[string]string{
+			"Authorization": "Bearer rotated",
+			"X-Trace":       "on",
+		},
+		cfg.Headers,
+	)
+}
+
+// The direction a naive "only set what was submitted" implementation
+// gets wrong: an emptied field must remove the stored value, not
+// leave the previous one in place.
+func assertEditClearingRemovesThem(
+	t *testing.T, env *sourceTestEnv,
+) {
+	t.Helper()
+
+	webhook, target := seedHTTPTarget(t, env, editAuthHeader, "7")
+
+	w := submitTargetEdit(
+		env, webhook.ID, target.ID,
+		editForm(editOriginalURL, "", ""),
+	)
+	require.Equal(t, http.StatusSeeOther, w.Code, w.Body.String())
+
+	cfg := storedHTTPConfig(t, env, target.ID)
+
+	assert.Empty(t, cfg.Headers)
+	assert.Zero(t, cfg.Timeout)
+}
+
+// Retries are offered only by the forms for target types that retry.
+// An absent field means the form does not edit retries, not that
+// they should be turned off.
+func assertEditKeepsAbsentMaxRetries(
+	t *testing.T, env *sourceTestEnv,
+) {
+	t.Helper()
+
+	webhook, target := seedHTTPTarget(t, env, "", "")
+	require.Equal(t, 3, target.MaxRetries)
+
+	form := editForm(editOriginalURL, "", "")
+	form.Del("max_retries")
+
+	w := submitTargetEdit(env, webhook.ID, target.ID, form)
+	require.Equal(t, http.StatusSeeOther, w.Code, w.Body.String())
+
+	assert.Equal(
+		t, 3, storedTarget(t, env, target.ID).MaxRetries,
+	)
+}
+
+// TestHandleTargetEdit_PrefillsTheStoredValuesUnmasked covers the
+// deliberate exception to the masking rule. The operator cannot
+// correct a value they cannot see, so this page — and only this page
+// — renders the destination and the header values in full.
+func TestHandleTargetEdit_PrefillsTheStoredValuesUnmasked(
+	t *testing.T,
+) {
+	t.Parallel()
+
+	env := setupSourceTest(t)
+
+	webhook, target := seedHTTPTarget(t, env, editAuthHeader, "7")
+
+	w := serveTarget(
+		env, http.MethodGet,
+		"/source/"+webhook.ID+"/targets/"+target.ID+"/edit",
+		nil,
+	)
+	require.Equal(t, http.StatusOK, w.Code)
+
+	page := w.Body.String()
+
+	assert.Contains(t, page, editOriginalURL)
+	assert.Contains(t, page, "Bearer "+editBearerSecret)
+	assert.Contains(t, page, `value="7"`)
+	assert.Contains(t, page, "original-name")
+}
+
+// TestHandleTargetEditSubmit_Rejects covers every submission that
+// must not reach storage.
+//
+// The SSRF case is the most important assertion on this change: the
+// edited destination goes through the same guard the create path
+// uses. An edit that stored an unvalidated URL would reopen a closed
+// hole, since a target could then be created public and edited to
+// point at loopback.
+//
+// The header and timeout cases keep input that could not be
+// delivered as written out of storage: a stored value that provably
+// never reaches the wire reports a configuration that did not take
+// effect.
+func TestHandleTargetEditSubmit_Rejects(t *testing.T) {
+	t.Parallel()
+
+	env := setupSourceTest(t)
+
+	t.Run("an SSRF-blocked destination", func(t *testing.T) {
+		t.Parallel()
+		assertEditRejectsBlockedDestination(t, env)
+	})
+
+	t.Run("a query-string destination", func(t *testing.T) {
+		t.Parallel()
+		assertEditIgnoresQueryString(t, env)
+	})
+
+	headerCases := map[string]string{
+		"no colon":        "Authorization Bearer token",
+		"empty name":      ": value",
+		"invalid name":    "X Bad Name: value",
+		"reserved header": "User-Agent: curl/8",
+		"duplicate name":  "X-A: one\nx-a: two",
+	}
+
+	for name, headers := range headerCases {
+		t.Run("headers: "+name, func(t *testing.T) {
+			t.Parallel()
+			assertEditRejectsHeaders(t, env, headers)
+		})
+	}
+
+	timeoutCases := map[string]string{
+		"not a number": "soon",
+		"negative":     "-1",
+		"over ceiling": "100000",
+	}
+
+	for name, timeout := range timeoutCases {
+		t.Run("timeout: "+name, func(t *testing.T) {
+			t.Parallel()
+			assertEditRejectsTimeout(t, env, timeout)
+		})
+	}
+}
+
+func assertEditRejectsBlockedDestination(
+	t *testing.T, env *sourceTestEnv,
+) {
+	t.Helper()
+
+	webhook, target := seedHTTPTarget(t, env, "", "")
+
+	w := submitTargetEdit(
+		env, webhook.ID, target.ID,
+		editForm(editBlockedURL, "", ""),
+	)
+
+	assert.Equal(t, http.StatusBadRequest, w.Code)
+	assert.Contains(t, w.Body.String(), "Invalid target URL")
+	assert.Equal(
+		t, editOriginalURL,
+		storedHTTPConfig(t, env, target.ID).URL,
+		"a rejected edit must leave the stored config alone",
+	)
+}
+
+// The ingress rule the create path already follows applies to the
+// edit path too: reading a field with FormValue would let the request
+// line carry the credential, and the request line is what logs,
+// proxies and Referer headers record.
+func assertEditIgnoresQueryString(
+	t *testing.T, env *sourceTestEnv,
+) {
+	t.Helper()
+
+	webhook, target := seedHTTPTarget(t, env, "", "")
+
+	form := url.Values{}
+	form.Set("name", "edited-name")
+
+	w := serveTarget(
+		env, http.MethodPost,
+		"/source/"+webhook.ID+"/targets/"+target.ID+
+			"/edit?url="+url.QueryEscape(editReplacedURL)+
+			"&headers="+url.QueryEscape(editAuthHeader),
+		form,
+	)
+
+	assert.Equal(t, http.StatusBadRequest, w.Code)
+
+	cfg := storedHTTPConfig(t, env, target.ID)
+	assert.Equal(t, editOriginalURL, cfg.URL)
+	assert.Empty(t, cfg.Headers)
+}
+
+func assertEditRejectsHeaders(
+	t *testing.T, env *sourceTestEnv, headers string,
+) {
+	t.Helper()
+
+	webhook, target := seedHTTPTarget(t, env, "", "")
+
+	w := submitTargetEdit(
+		env, webhook.ID, target.ID,
+		editForm(editOriginalURL, headers, ""),
+	)
+
+	assert.Equal(t, http.StatusBadRequest, w.Code)
+	assert.Contains(t, w.Body.String(), "Invalid headers")
+	assert.Empty(
+		t, storedHTTPConfig(t, env, target.ID).Headers,
+		"a rejected header must not be stored",
+	)
+}
+
+func assertEditRejectsTimeout(
+	t *testing.T, env *sourceTestEnv, timeout string,
+) {
+	t.Helper()
+
+	webhook, target := seedHTTPTarget(t, env, "", "9")
+
+	w := submitTargetEdit(
+		env, webhook.ID, target.ID,
+		editForm(editOriginalURL, "", timeout),
+	)
+
+	assert.Equal(t, http.StatusBadRequest, w.Code)
+	assert.Contains(t, w.Body.String(), "Invalid timeout")
+	assert.Equal(
+		t, 9, storedHTTPConfig(t, env, target.ID).Timeout,
+		"a rejected timeout must leave the stored one alone",
+	)
+}
+
+// TestHandleTargetEdit_Scoping keeps the edit routes scoped the way
+// the delete and toggle routes are: ownership is decided by the
+// webhook, and the target is then scoped to it.
+func TestHandleTargetEdit_Scoping(t *testing.T) {
+	t.Parallel()
+
+	env := setupSourceTest(t)
+
+	t.Run("a target of another webhook", func(t *testing.T) {
+		t.Parallel()
+		assertTargetOfAnotherWebhook404s(t, env)
+	})
+
+	t.Run("a webhook of another user", func(t *testing.T) {
+		t.Parallel()
+		assertWebhookOfAnotherUser404s(t, env)
+	})
+}
+
+// A target id from elsewhere must not become editable by pairing it
+// with a webhook the user does own.
+func assertTargetOfAnotherWebhook404s(
+	t *testing.T, env *sourceTestEnv,
+) {
+	t.Helper()
+
+	mine := seedWebhookWithRetention(t, env.db, 30)
+	_, target := seedHTTPTarget(t, env, "", "")
+
+	get := serveTarget(
+		env, http.MethodGet,
+		"/source/"+mine.ID+"/targets/"+target.ID+"/edit", nil,
+	)
+	assert.Equal(t, http.StatusNotFound, get.Code)
+
+	post := submitTargetEdit(
+		env, mine.ID, target.ID,
+		editForm(editReplacedURL, "", ""),
+	)
+	assert.Equal(t, http.StatusNotFound, post.Code)
+
+	assert.Equal(
+		t, editOriginalURL,
+		storedHTTPConfig(t, env, target.ID).URL,
+	)
+}
+
+func assertWebhookOfAnotherUser404s(
+	t *testing.T, env *sourceTestEnv,
+) {
+	t.Helper()
+
+	other := &database.Webhook{
+		UserID:        "some-other-user",
+		Name:          "not mine",
+		RetentionDays: 30,
+	}
+	require.NoError(
+		t,
+		env.db.DB().Omit(clause.Associations).Create(other).Error,
+	)
+
+	target := seedConfiguredTarget(
+		t, env.db, other.ID, database.TargetTypeHTTP,
+		`{"url":"`+editOriginalURL+`"}`,
+	)
+
+	w := serveTarget(
+		env, http.MethodGet,
+		"/source/"+other.ID+"/targets/"+target.ID+"/edit", nil,
+	)
+
+	assert.Equal(t, http.StatusNotFound, w.Code)
+}

internal/handlers/webhook.go

@@ -217,6 +217,11 @@ func (h *Handlers) createAndDeliverEvent(
 		return
 	}
 
+	// Counted here, after the commit: an event is received once it
+	// is durably stored, which is what the delivery counters are
+	// compared against on a dashboard.
+	h.mtr.EventReceived()
+
 	h.finishWebhookResponse(w, event, entrypoint, tasks)
 }
 

internal/metrics/metrics.go

@@ -0,0 +1,344 @@
+// Package metrics defines the Prometheus collectors describing
+// webhooker's delivery pipeline: how many events arrive, how many
+// deliveries are attempted, how they end, how long they take, how
+// deep the queues are, and how many circuit breakers are open.
+//
+// The inbound HTTP metrics come from the go-http-metrics recorder in
+// internal/middleware and land on prometheus.DefaultRegisterer. These
+// collectors register there too, so both surfaces are gathered by the
+// one promhttp handler mounted on the authenticated /metrics route.
+package metrics
+
+import (
+	"sync"
+	"time"
+
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promauto"
+	"sneak.berlin/go/webhooker/internal/database"
+)
+
+// namespace prefixes every collector defined here.
+const namespace = "webhooker"
+
+// targetTypeLabel is the only label any delivery metric carries, and
+// cardinality is the whole reason for that.
+//
+// A target type is one of four compile-time constants, so the label
+// domain is bounded by construction. Target ids, event ids and
+// entrypoint ids are not: they are UUIDs minted per operator action
+// or per inbound request, a series is never reclaimed once it exists,
+// and labelling by any of them makes /metrics a memory leak that
+// grows with traffic. normalizeTargetType enforces the bound at every
+// call site — a type the registry does not know collapses into
+// unknownTargetType rather than minting a series of its own.
+const targetTypeLabel = "target_type"
+
+// unknownTargetType is the bucket for a target type outside the known
+// set, so an unrecognised value cannot mint a new series.
+const unknownTargetType = "unknown"
+
+// Delivery duration buckets, exponential from 5ms so the last bucket
+// (about 98s) sits above the 30s outbound HTTP client timeout.
+const (
+	durationBucketStart  = 0.005
+	durationBucketFactor = 3
+	durationBucketCount  = 10
+)
+
+// knownTargetTypes is the fixed label domain: the target types the
+// delivery engine implements.
+//
+//nolint:gochecknoglobals // the label domain, built once per process
+var knownTargetTypes = []database.TargetType{
+	database.TargetTypeHTTP,
+	database.TargetTypeDatabase,
+	database.TargetTypeLog,
+	database.TargetTypeSlack,
+}
+
+// defaultSet is the process-wide metric set, registered on the same
+// registry the HTTP middleware and the /metrics handler already use.
+// It is built on first use rather than in an init so that a test
+// binary that never touches metrics never registers them.
+//
+//nolint:gochecknoglobals // one process-wide registration, by design
+var defaultSet = sync.OnceValue(func() *Set {
+	return New(prometheus.DefaultRegisterer)
+})
+
+// Default returns the process-wide metric set.
+func Default() *Set {
+	return defaultSet()
+}
+
+// Set is one registered group of webhooker's delivery collectors.
+// Production uses the single Default set; tests build their own
+// against a private registry so assertions are not disturbed by
+// deliveries other tests are making concurrently.
+type Set struct {
+	eventsReceived      prometheus.Counter
+	deliveryAttempts    *prometheus.CounterVec
+	deliveriesSucceeded *prometheus.CounterVec
+	deliveriesFailed    *prometheus.CounterVec
+	deliveryRetries     *prometheus.CounterVec
+	deliveryDuration    *prometheus.HistogramVec
+	deliveriesPending   *prometheus.GaugeVec
+	deliveriesRetrying  *prometheus.GaugeVec
+	circuitBreakersOpen *prometheus.GaugeVec
+}
+
+// New registers a full set of delivery collectors on reg and returns
+// it. It panics if reg already holds them, which is the intended
+// behaviour for a duplicate registration.
+func New(reg prometheus.Registerer) *Set {
+	factory := promauto.With(reg)
+
+	s := &Set{
+		eventsReceived: factory.NewCounter(
+			prometheus.CounterOpts{
+				Namespace: namespace,
+				Name:      "events_received_total",
+				Help: "Webhook events received and " +
+					"stored, so the receive and deliver " +
+					"sides can be compared.",
+			},
+		),
+		deliveryDuration: factory.NewHistogramVec(
+			prometheus.HistogramOpts{
+				Namespace: namespace,
+				Name:      "delivery_duration_seconds",
+				Help: "Wall time of a single delivery " +
+					"attempt, by target type.",
+				Buckets: prometheus.ExponentialBuckets(
+					durationBucketStart,
+					durationBucketFactor,
+					durationBucketCount,
+				),
+			},
+			[]string{targetTypeLabel},
+		),
+	}
+
+	s.registerCounters(factory)
+	s.registerGauges(factory)
+	s.initSeries()
+
+	return s
+}
+
+// EventReceived counts one inbound webhook event stored.
+func (s *Set) EventReceived() {
+	s.eventsReceived.Inc()
+}
+
+// DeliveryAttempted counts one delivery attempt dispatched to a
+// target.
+func (s *Set) DeliveryAttempted(t database.TargetType) {
+	s.deliveryAttempts.
+		WithLabelValues(normalizeTargetType(t)).
+		Inc()
+}
+
+// ObserveDeliveryDuration records how long one delivery attempt took.
+func (s *Set) ObserveDeliveryDuration(
+	t database.TargetType, d time.Duration,
+) {
+	s.deliveryDuration.
+		WithLabelValues(normalizeTargetType(t)).
+		Observe(d.Seconds())
+}
+
+// DeliveryStatusChanged counts a delivery's transition into a new
+// status. The mapping from status to counter lives here, next to the
+// collectors, so the engine has a single call for every transition it
+// persists. A move back to pending is not an outcome and counts
+// nothing.
+func (s *Set) DeliveryStatusChanged(
+	t database.TargetType, status database.DeliveryStatus,
+) {
+	label := normalizeTargetType(t)
+
+	switch status {
+	case database.DeliveryStatusDelivered:
+		s.deliveriesSucceeded.WithLabelValues(label).Inc()
+	case database.DeliveryStatusFailed:
+		s.deliveriesFailed.WithLabelValues(label).Inc()
+	case database.DeliveryStatusRetrying:
+		s.deliveryRetries.WithLabelValues(label).Inc()
+	case database.DeliveryStatusPending:
+	}
+}
+
+// SetQueueDepths publishes the pending and retrying queue depths from
+// one sample. Every label in the queue domain is written on every
+// call, so a type whose queue has drained reads zero instead of
+// holding its last value forever.
+func (s *Set) SetQueueDepths(
+	pending, retrying map[database.TargetType]int,
+) {
+	pendingByLabel := foldToLabels(pending)
+	retryingByLabel := foldToLabels(retrying)
+
+	for _, label := range queueDepthLabels() {
+		s.deliveriesPending.WithLabelValues(label).
+			Set(float64(pendingByLabel[label]))
+		s.deliveriesRetrying.WithLabelValues(label).
+			Set(float64(retryingByLabel[label]))
+	}
+}
+
+// queueDepthLabels is the label domain of the two queue-depth gauges:
+// the known target types plus unknown.
+//
+// Unknown is a real bucket here, not a safety net. A delivery queued
+// against a target that has since been deleted carries a target id no
+// longer in the targets table, so the sample resolves it to the empty
+// type; folding it into unknown is what keeps that backlog visible.
+// Dropping it would hide the one queue nobody is watching.
+func queueDepthLabels() []string {
+	labels := make([]string, 0, len(knownTargetTypes)+1)
+
+	for _, t := range knownTargetTypes {
+		labels = append(labels, string(t))
+	}
+
+	return append(labels, unknownTargetType)
+}
+
+// foldToLabels collapses a per-target-type count onto the bounded
+// label domain, summing everything outside the known set into
+// unknown.
+func foldToLabels(
+	counts map[database.TargetType]int,
+) map[string]int {
+	byLabel := make(map[string]int, len(counts))
+
+	for t, n := range counts {
+		byLabel[normalizeTargetType(t)] += n
+	}
+
+	return byLabel
+}
+
+// SetCircuitBreakersOpen publishes how many of a target type's
+// circuit breakers are currently open.
+func (s *Set) SetCircuitBreakersOpen(
+	t database.TargetType, open int,
+) {
+	s.circuitBreakersOpen.
+		WithLabelValues(normalizeTargetType(t)).
+		Set(float64(open))
+}
+
+func (s *Set) registerCounters(factory promauto.Factory) {
+	s.deliveryAttempts = factory.NewCounterVec(
+		prometheus.CounterOpts{
+			Namespace: namespace,
+			Name:      "delivery_attempts_total",
+			Help: "Delivery attempts dispatched to a " +
+				"target, by target type.",
+		},
+		[]string{targetTypeLabel},
+	)
+
+	s.deliveriesSucceeded = factory.NewCounterVec(
+		prometheus.CounterOpts{
+			Namespace: namespace,
+			Name:      "deliveries_succeeded_total",
+			Help: "Deliveries that reached the delivered " +
+				"state, by target type.",
+		},
+		[]string{targetTypeLabel},
+	)
+
+	s.deliveriesFailed = factory.NewCounterVec(
+		prometheus.CounterOpts{
+			Namespace: namespace,
+			Name:      "deliveries_failed_total",
+			Help: "Deliveries that failed terminally and " +
+				"will not be retried, by target type.",
+		},
+		[]string{targetTypeLabel},
+	)
+
+	s.deliveryRetries = factory.NewCounterVec(
+		prometheus.CounterOpts{
+			Namespace: namespace,
+			Name:      "delivery_retries_total",
+			Help: "Deliveries put back into the retrying " +
+				"state, by target type.",
+		},
+		[]string{targetTypeLabel},
+	)
+}
+
+func (s *Set) registerGauges(factory promauto.Factory) {
+	s.deliveriesPending = factory.NewGaugeVec(
+		prometheus.GaugeOpts{
+			Namespace: namespace,
+			Name:      "deliveries_pending",
+			Help: "Deliveries currently in the pending " +
+				"state, by target type.",
+		},
+		[]string{targetTypeLabel},
+	)
+
+	s.deliveriesRetrying = factory.NewGaugeVec(
+		prometheus.GaugeOpts{
+			Namespace: namespace,
+			Name:      "deliveries_retrying",
+			Help: "Deliveries currently in the retrying " +
+				"state, by target type.",
+		},
+		[]string{targetTypeLabel},
+	)
+
+	s.circuitBreakersOpen = factory.NewGaugeVec(
+		prometheus.GaugeOpts{
+			Namespace: namespace,
+			Name:      "circuit_breakers_open",
+			Help: "Delivery circuit breakers currently " +
+				"open, by target type.",
+		},
+		[]string{targetTypeLabel},
+	)
+}
+
+// initSeries materialises every known-target-type series at zero, so
+// a dashboard and an alert rule see a target type that has not
+// delivered yet rather than a missing series.
+//
+// The queue-depth gauges additionally get their unknown series, which
+// holds deliveries queued against a deleted target. That backlog can
+// predate the process — it is read out of the databases, not counted
+// from transitions — so its series has to exist from the first scrape
+// rather than appearing only once a backlog has already built up.
+func (s *Set) initSeries() {
+	for _, t := range knownTargetTypes {
+		label := string(t)
+
+		s.deliveryAttempts.WithLabelValues(label)
+		s.deliveriesSucceeded.WithLabelValues(label)
+		s.deliveriesFailed.WithLabelValues(label)
+		s.deliveryRetries.WithLabelValues(label)
+		s.deliveriesPending.WithLabelValues(label)
+		s.deliveriesRetrying.WithLabelValues(label)
+		s.circuitBreakersOpen.WithLabelValues(label)
+	}
+
+	s.deliveriesPending.WithLabelValues(unknownTargetType)
+	s.deliveriesRetrying.WithLabelValues(unknownTargetType)
+}
+
+// normalizeTargetType maps a target type onto the bounded label
+// domain, collapsing anything outside it to unknownTargetType.
+func normalizeTargetType(t database.TargetType) string {
+	for _, known := range knownTargetTypes {
+		if t == known {
+			return string(known)
+		}
+	}
+
+	return unknownTargetType
+}

internal/metrics/metrics_test.go

@@ -0,0 +1,285 @@
+package metrics_test
+
+import (
+	"testing"
+
+	"github.com/prometheus/client_golang/prometheus"
+	dto "github.com/prometheus/client_model/go"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"sneak.berlin/go/webhooker/internal/database"
+	"sneak.berlin/go/webhooker/internal/metrics"
+)
+
+// knownLabels is the target_type label domain built from the target
+// types the delivery engine implements.
+func knownLabels() []string {
+	return []string{"http", "database", "log", "slack"}
+}
+
+// labelValues returns the target_type label values a metric family
+// currently carries.
+func labelValues(
+	t *testing.T, reg *prometheus.Registry, name string,
+) []string {
+	t.Helper()
+
+	families, err := reg.Gather()
+	require.NoError(t, err)
+
+	var values []string
+
+	for _, fam := range families {
+		if fam.GetName() != name {
+			continue
+		}
+
+		for _, m := range fam.GetMetric() {
+			for _, label := range m.GetLabel() {
+				if label.GetName() == "target_type" {
+					values = append(
+						values, label.GetValue(),
+					)
+				}
+			}
+		}
+	}
+
+	return values
+}
+
+func gaugeValue(
+	t *testing.T,
+	reg *prometheus.Registry,
+	name, targetType string,
+) float64 {
+	t.Helper()
+
+	families, err := reg.Gather()
+	require.NoError(t, err)
+
+	for _, fam := range families {
+		if fam.GetName() != name {
+			continue
+		}
+
+		for _, m := range fam.GetMetric() {
+			if hasTargetType(m, targetType) {
+				return m.GetGauge().GetValue()
+			}
+		}
+	}
+
+	t.Fatalf(
+		"gauge %s{target_type=%q} not found",
+		name, targetType,
+	)
+
+	return 0
+}
+
+func hasTargetType(m *dto.Metric, targetType string) bool {
+	for _, label := range m.GetLabel() {
+		if label.GetName() == "target_type" &&
+			label.GetValue() == targetType {
+			return true
+		}
+	}
+
+	return false
+}
+
+// TestUnknownTargetTypeCollapses is the cardinality guard: a target
+// type outside the known set must not mint a series of its own, or
+// /metrics grows without bound.
+func TestUnknownTargetTypeCollapses(t *testing.T) {
+	t.Parallel()
+
+	reg := prometheus.NewRegistry()
+	set := metrics.New(reg)
+
+	for _, bogus := range []string{
+		"a1b2c3d4-0000-0000-0000-000000000001",
+		"a1b2c3d4-0000-0000-0000-000000000002",
+		"webhook-forwarder",
+	} {
+		set.DeliveryAttempted(database.TargetType(bogus))
+	}
+
+	values := labelValues(
+		t, reg, "webhooker_delivery_attempts_total",
+	)
+
+	assert.ElementsMatch(t,
+		append(knownLabels(), "unknown"),
+		values,
+	)
+}
+
+// TestSetQueueDepthsZeroesDrainedTypes proves a queue that has
+// drained reads zero rather than holding its last sample forever.
+func TestSetQueueDepthsZeroesDrainedTypes(t *testing.T) {
+	t.Parallel()
+
+	reg := prometheus.NewRegistry()
+	set := metrics.New(reg)
+
+	set.SetQueueDepths(
+		map[database.TargetType]int{
+			database.TargetTypeHTTP: 7,
+		},
+		map[database.TargetType]int{
+			database.TargetTypeSlack: 2,
+		},
+	)
+
+	assert.InDelta(t, 7.0, gaugeValue(
+		t, reg, "webhooker_deliveries_pending", "http",
+	), 0)
+	assert.InDelta(t, 2.0, gaugeValue(
+		t, reg, "webhooker_deliveries_retrying", "slack",
+	), 0)
+
+	set.SetQueueDepths(
+		map[database.TargetType]int{},
+		map[database.TargetType]int{},
+	)
+
+	assert.InDelta(t, 0.0, gaugeValue(
+		t, reg, "webhooker_deliveries_pending", "http",
+	), 0)
+	assert.InDelta(t, 0.0, gaugeValue(
+		t, reg, "webhooker_deliveries_retrying", "slack",
+	), 0)
+}
+
+// TestKnownSeriesExistBeforeAnyDelivery proves every known target
+// type is published at zero from registration, so an alert rule does
+// not have to cope with a missing series.
+func TestKnownSeriesExistBeforeAnyDelivery(t *testing.T) {
+	t.Parallel()
+
+	reg := prometheus.NewRegistry()
+	metrics.New(reg)
+
+	for _, name := range []string{
+		"webhooker_delivery_attempts_total",
+		"webhooker_deliveries_succeeded_total",
+		"webhooker_deliveries_failed_total",
+		"webhooker_delivery_retries_total",
+		"webhooker_circuit_breakers_open",
+	} {
+		assert.ElementsMatch(t,
+			knownLabels(),
+			labelValues(t, reg, name),
+			"metric %s", name,
+		)
+	}
+
+	// The queue gauges additionally publish unknown from
+	// registration: a backlog queued against a deleted target lands
+	// there, and it can predate the process, so the series has to
+	// exist before the first sample rather than appearing only once
+	// something is already stuck.
+	for _, name := range []string{
+		"webhooker_deliveries_pending",
+		"webhooker_deliveries_retrying",
+	} {
+		assert.ElementsMatch(t,
+			append(knownLabels(), "unknown"),
+			labelValues(t, reg, name),
+			"metric %s", name,
+		)
+	}
+}
+
+// TestSetQueueDepthsFoldsUnknownTypes proves a queued delivery whose
+// target type is not a known one — a target deleted out from under it
+// resolves to the empty type — is summed into the unknown series
+// instead of being dropped, and that the fold is a sum rather than a
+// last-writer-wins.
+func TestSetQueueDepthsFoldsUnknownTypes(t *testing.T) {
+	t.Parallel()
+
+	reg := prometheus.NewRegistry()
+	set := metrics.New(reg)
+
+	set.SetQueueDepths(
+		map[database.TargetType]int{
+			database.TargetTypeHTTP:             1,
+			database.TargetType(""):             4,
+			database.TargetType("retired-type"): 3,
+		},
+		map[database.TargetType]int{
+			database.TargetType(""): 2,
+		},
+	)
+
+	assert.InDelta(t, 7.0, gaugeValue(
+		t, reg, "webhooker_deliveries_pending", "unknown",
+	), 0)
+	assert.InDelta(t, 2.0, gaugeValue(
+		t, reg, "webhooker_deliveries_retrying", "unknown",
+	), 0)
+	assert.InDelta(t, 1.0, gaugeValue(
+		t, reg, "webhooker_deliveries_pending", "http",
+	), 0)
+
+	set.SetQueueDepths(
+		map[database.TargetType]int{},
+		map[database.TargetType]int{},
+	)
+
+	assert.InDelta(t, 0.0, gaugeValue(
+		t, reg, "webhooker_deliveries_pending", "unknown",
+	), 0)
+}
+
+// TestDeliveryStatusChangedCounts maps each persisted status onto the
+// counter it moves.
+func TestDeliveryStatusChangedCounts(t *testing.T) {
+	t.Parallel()
+
+	reg := prometheus.NewRegistry()
+	set := metrics.New(reg)
+
+	set.DeliveryStatusChanged(
+		database.TargetTypeLog,
+		database.DeliveryStatusDelivered,
+	)
+	set.DeliveryStatusChanged(
+		database.TargetTypeLog,
+		database.DeliveryStatusFailed,
+	)
+	set.DeliveryStatusChanged(
+		database.TargetTypeLog,
+		database.DeliveryStatusRetrying,
+	)
+	set.DeliveryStatusChanged(
+		database.TargetTypeLog,
+		database.DeliveryStatusPending,
+	)
+
+	families, err := reg.Gather()
+	require.NoError(t, err)
+
+	counts := map[string]float64{}
+
+	for _, fam := range families {
+		for _, m := range fam.GetMetric() {
+			if hasTargetType(m, "log") {
+				counts[fam.GetName()] =
+					m.GetCounter().GetValue()
+			}
+		}
+	}
+
+	assert.InDelta(t, 1.0,
+		counts["webhooker_deliveries_succeeded_total"], 0)
+	assert.InDelta(t, 1.0,
+		counts["webhooker_deliveries_failed_total"], 0)
+	assert.InDelta(t, 1.0,
+		counts["webhooker_delivery_retries_total"], 0)
+	assert.InDelta(t, 0.0,
+		counts["webhooker_delivery_attempts_total"], 0)
+}

internal/server/routes.go

@@ -214,6 +214,20 @@ func (s *Server) setupSourceRoutes() {
 			s.h.HandleEntrypointToggle(),
 		)
 		r.Post("/targets", s.h.HandleTargetCreate())
+		// The edit form is the one page that renders a target's
+		// destination URL and header values in full; see
+		// delivery.TargetConfigForm. It belongs to this group for
+		// its RequireAuth and NoCache, which are what keep that
+		// exception from reaching an unauthenticated request or a
+		// shared cache.
+		r.Get(
+			"/targets/{targetID}/edit",
+			s.h.HandleTargetEdit(),
+		)
+		r.Post(
+			"/targets/{targetID}/edit",
+			s.h.HandleTargetEditSubmit(),
+		)
 		r.Post(
 			"/targets/{targetID}/delete",
 			s.h.HandleTargetDelete(),

templates/source_detail.html

@@ -110,6 +110,14 @@
                     <div x-show="targetType === 'http'">
                         <input type="url" name="url" placeholder="https://example.com/webhook" :disabled="targetType !== 'http'" class="input text-sm">
                     </div>
+                    <div x-show="targetType === 'http'">
+                        <textarea name="headers" rows="3" placeholder="Authorization: Bearer ..." :disabled="targetType !== 'http'" class="input text-sm"></textarea>
+                        <p class="text-xs text-gray-500 mt-1">Optional request headers, one <code>Name: value</code> per line, sent with every delivery.</p>
+                    </div>
+                    <div x-show="targetType === 'http'" class="flex gap-2 items-center">
+                        <label class="text-sm text-gray-700">Timeout (seconds, blank = default):</label>
+                        <input type="number" name="timeout" min="0" max="300" :disabled="targetType !== 'http'" class="input text-sm w-24">
+                    </div>
                     <div x-show="targetType === 'http'" class="flex gap-2 items-center">
                         <label class="text-sm text-gray-700">Max retries (0 = fire-and-forget):</label>
                         <input type="number" name="max_retries" value="0" min="0" max="20" class="input text-sm w-24">
@@ -138,6 +146,7 @@
                             {{else}}
                             <span class="badge-error">Inactive</span>
                             {{end}}
+                            <a href="/source/{{$.Webhook.ID}}/targets/{{.ID}}/edit" class="text-xs text-gray-500 hover:text-primary-600" title="Edit">Edit</a>
                             <form method="POST" action="/source/{{$.Webhook.ID}}/targets/{{.ID}}/toggle" class="inline">
                                 <input type="hidden" name="csrf_token" value="{{$.CSRFToken}}">
                                 <button type="submit" class="text-xs text-gray-500 hover:text-primary-600" title="{{if .Active}}Deactivate{{else}}Activate{{end}}">

templates/source_logs.html

@@ -40,6 +40,61 @@
                     {{if .BodyTruncated}}
                     <p class="mt-2 text-xs text-gray-500">Body truncated for display: showing {{.BodyShownBytes}} of {{.BodyBytes}} bytes. The stored body is unchanged &mdash; <a href="/source/{{$.Webhook.ID}}/logs/{{.ID}}/body" class="text-primary-600 hover:text-primary-700 underline">download the full body</a>.</p>
                     {{end}}
+
+                    {{if .Deliveries}}
+                    <div class="mt-4 border-t border-gray-200 pt-3">
+                        <h3 class="text-xs font-medium uppercase tracking-wide text-gray-500">Deliveries</h3>
+                        <div class="mt-2 divide-y divide-gray-200">
+                            {{range .Deliveries}}
+                            <div class="py-2" x-data="{ attempts: false }">
+                                <div class="flex items-center justify-between cursor-pointer" @click="attempts = !attempts">
+                                    <div class="flex items-center gap-3">
+                                        <span class="text-sm text-gray-700">{{.Target.Name}}</span>
+                                        <span class="text-xs {{if eq .Status "delivered"}}text-green-600{{else if eq .Status "failed"}}text-red-600{{else if eq .Status "retrying"}}text-yellow-600{{else}}text-gray-400{{end}}">{{.Status}}</span>
+                                    </div>
+                                    <div class="flex items-center gap-2">
+                                        <span class="text-xs text-gray-400">{{.AttemptCount}} attempt{{if ne .AttemptCount 1}}s{{end}}</span>
+                                        <svg class="w-3 h-3 text-gray-400 transition-transform" :class="{ 'rotate-180': attempts }" fill="none" stroke="currentColor" viewBox="0 0 24 24">
+                                            <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M19 9l-7 7-7-7"/>
+                                        </svg>
+                                    </div>
+                                </div>
+
+                                <div x-show="attempts" x-cloak class="mt-2 space-y-2">
+                                    {{if .AttemptsOmitted}}
+                                    <p class="text-xs text-gray-500">{{.AttemptsOmitted}} attempt{{if ne .AttemptsOmitted 1}}s{{end}} omitted between the first and last shown.</p>
+                                    {{end}}
+                                    {{range .Results}}
+                                    <div class="rounded-md bg-white border border-gray-200 p-2">
+                                        <div class="flex flex-wrap items-center gap-3 text-xs">
+                                            <span class="text-gray-500">Attempt {{.AttemptNum}}</span>
+                                            <span class="{{if .Success}}text-green-600{{else}}text-red-600{{end}}">{{if .Success}}success{{else}}failure{{end}}</span>
+                                            <span class="text-gray-500">Status: {{if .HasStatusCode}}{{.StatusCode}}{{else}}&mdash; (no response){{end}}</span>
+                                            <span class="text-gray-500">Duration: {{.DurationMS}} ms</span>
+                                        </div>
+                                        {{if .Error}}
+                                        <p class="mt-2 text-xs text-red-700 break-all">Error: {{.Error}}</p>
+                                        {{end}}
+                                        {{if .ResponseBody}}
+                                        <pre class="mt-2 text-xs text-gray-700 overflow-x-auto whitespace-pre-wrap break-all">{{.ResponseBody}}</pre>
+                                        {{end}}
+                                        {{if .ResponseTruncated}}
+                                        {{if .ResponseSizeKnown}}
+                                        <p class="mt-1 text-xs text-gray-500">Response truncated for display: showing {{.ResponseShownBytes}} of {{.ResponseBytes}} bytes.</p>
+                                        {{else}}
+                                        <p class="mt-1 text-xs text-gray-500">Showing {{.ResponseShownBytes}} of the {{.ResponseBytes}} recorded bytes. The response reached the recording limit, so the remote may have sent more that was never stored.</p>
+                                        {{end}}
+                                        {{end}}
+                                    </div>
+                                    {{else}}
+                                    <p class="text-xs text-gray-500">No attempts recorded yet.</p>
+                                    {{end}}
+                                </div>
+                            </div>
+                            {{end}}
+                        </div>
+                    </div>
+                    {{end}}
                 </div>
             </div>
             {{else}}

templates/target_edit.html

@@ -0,0 +1,83 @@
+{{template "base" .}}
+
+{{define "title"}}Edit {{.Target.Name}} - Webhooker{{end}}
+
+{{define "content"}}
+<div class="max-w-2xl mx-auto px-6 py-8">
+    <div class="mb-6">
+        <a href="/source/{{.Webhook.ID}}" class="text-sm text-primary-600 hover:text-primary-700">&larr; Back to {{.Webhook.Name}}</a>
+        <h1 class="text-2xl font-medium text-gray-900 mt-2">Edit Target</h1>
+        <p class="text-sm text-gray-500 mt-1">Type: {{.Target.Type}}. A target's type cannot be changed; create a new target to deliver a different way.</p>
+    </div>
+
+    <div class="card p-6">
+        {{if .Error}}
+        <div class="alert-error">{{.Error}}</div>
+        {{end}}
+
+        {{if or (eq .Target.Type "http") (eq .Target.Type "slack")}}
+        <div class="mb-6 rounded-md bg-gray-50 p-4 text-sm text-gray-700">
+            This form shows the target's stored destination in full, including any credential carried in its URL or headers. It is the only page that does; everywhere else the value is masked.
+        </div>
+        {{end}}
+
+        <form method="POST" action="/source/{{.Webhook.ID}}/targets/{{.Target.ID}}/edit" class="space-y-6">
+            <input type="hidden" name="csrf_token" value="{{.CSRFToken}}">
+
+            <div class="form-group">
+                <label for="name" class="label">Name</label>
+                <input type="text" id="name" name="name" value="{{.Target.Name}}" required class="input">
+            </div>
+
+            {{if eq .Target.Type "http"}}
+            <div class="form-group">
+                <label for="url" class="label">Destination URL</label>
+                <input type="url" id="url" name="url" value="{{.Target.Config.URL}}" required class="input">
+                <p class="text-xs text-gray-500 mt-1">Revalidated on save; destinations that resolve to private or link-local addresses are rejected.</p>
+            </div>
+
+            <div class="form-group">
+                <label for="headers" class="label">Headers</label>
+                <textarea id="headers" name="headers" rows="4" class="input" placeholder="Authorization: Bearer ...">{{.Target.Config.Headers}}</textarea>
+                <p class="text-xs text-gray-500 mt-1">One <code>Name: value</code> per line, sent with every delivery. Leave blank for none. <code>Host</code>, <code>Content-Length</code>, <code>Transfer-Encoding</code>, <code>Connection</code> and <code>User-Agent</code> are set by the delivery engine and are rejected here rather than silently ignored.</p>
+            </div>
+
+            <div class="form-group">
+                <label for="timeout" class="label">Timeout (seconds)</label>
+                <input type="number" id="timeout" name="timeout" value="{{.Target.Config.Timeout}}" min="0" max="{{.MaxTimeout}}" class="input">
+                <p class="text-xs text-gray-500 mt-1">Per-request timeout, at most {{.MaxTimeout}} seconds. Leave blank to use the default.</p>
+            </div>
+            {{end}}
+
+            {{if eq .Target.Type "slack"}}
+            <div class="form-group">
+                <label for="url" class="label">Webhook URL</label>
+                <input type="url" id="url" name="url" value="{{.Target.Config.URL}}" required class="input">
+                <p class="text-xs text-gray-500 mt-1">Slack or Mattermost incoming webhook URL. Revalidated on save.</p>
+            </div>
+            {{end}}
+
+            {{if eq .Target.Type "database"}}
+            <div class="form-group">
+                <label for="expiry" class="label">Archive Expiry</label>
+                <input type="text" id="expiry" name="expiry" value="{{.Target.Config.Expiry}}" placeholder="never" class="input">
+                <p class="text-xs text-gray-500 mt-1">"never" (the default when blank) keeps archived rows forever, or a Go duration like "720h" prunes older rows.</p>
+            </div>
+            {{end}}
+
+            {{if or (eq .Target.Type "http") (eq .Target.Type "slack")}}
+            <div class="form-group">
+                <label for="max_retries" class="label">Max retries</label>
+                <input type="number" id="max_retries" name="max_retries" value="{{.Target.MaxRetries}}" min="0" max="20" class="input">
+                <p class="text-xs text-gray-500 mt-1">0 is fire-and-forget: one attempt, no circuit breaker.</p>
+            </div>
+            {{end}}
+
+            <div class="flex gap-3">
+                <button type="submit" class="btn-primary">Save Changes</button>
+                <a href="/source/{{.Webhook.ID}}" class="btn-secondary">Cancel</a>
+            </div>
+        </form>
+    </div>
+</div>
+{{end}}