Say what each action did in a one-line notice (closes #383)

Every action on the webhook pages, and signing out, redirects with a
fixed notice code in the URL, and the page it lands on shows one line
saying what was done. noticeFor maps codes to fixed text and an
unknown code shows nothing, so nothing from the URL is echoed. One
partial, templates/notice.html, shows the line under the navbar on
every page; the error page shows none.

Replay and resubmit use the same codes and partial in place of their
own query parameters and event log banners.

Model: opus-5-5

README.md

@@ -2951,13 +2951,15 @@ Components are wired via Uber fx in this order:
 7. `healthcheck.New` — Health check service
 8. `session.New` — Cookie-based session manager (key from database)
 9. `handlers.New` — HTTP handlers
-10. `middleware.New` — HTTP middleware
-11. `delivery.New` — Event-driven delivery engine
-12. `delivery.NewArchiveSweeper` — Periodic pruning of idle archives
-13. `delivery.Engine` → `delivery.Notifier` — interface bridge
-14. `delivery.Engine` → `delivery.WebhookEvictor` — interface bridge so
+10. `metrics.NewRegistry` — The registry `/metrics` serves
+11. `metrics.New` — The delivery collectors, registered on that registry
+12. `middleware.New` — HTTP middleware
+13. `delivery.New` — Event-driven delivery engine
+14. `delivery.NewArchiveSweeper` — Periodic pruning of idle archives
+15. `delivery.Engine` → `delivery.Notifier` — interface bridge
+16. `delivery.Engine` → `delivery.WebhookEvictor` — interface bridge so
     deleting a webhook releases its archive writer
-15. `server.New` — HTTP server and router
+17. `server.New` — HTTP server and router
 
 The server starts via `fx.Invoke(func(*server.Server, *delivery.Engine,
 *database.RetentionReaper, *delivery.ArchiveSweeper) {})`, which

TODO.md

@@ -40,12 +40,6 @@ duplicate. That is deliberate — the alternative is a silent lost
 delivery — and the README says so under Rationale. It is not a defect
 to re-file.
 
-One caveat on reading a green check: a docs-only commit deliberately
-replays from the layer cache
-(https://git.eeqj.de/sneak/webhooker/issues/119), so a green status on
-such a commit evidences a replay rather than an executed run. A code
-commit invalidates the `COPY` layer and genuinely executes.
-
 # Next Step
 
 Clear the rest of the open 1.0.0 milestone

cmd/webhooker/main.go

@@ -16,6 +16,7 @@ import (
 	"sneak.berlin/go/webhooker/internal/handlers"
 	"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/resetpw"
 	"sneak.berlin/go/webhooker/internal/server"
@@ -177,6 +178,10 @@ func newApp() *fx.App {
 			healthcheck.New,
 			session.New,
 			handlers.New,
+			// The registry /metrics serves, and the delivery
+			// collectors registered on it.
+			metrics.NewRegistry,
+			metrics.New,
 			middleware.New,
 			// The one SSRF guard both target-creation validation
 			// and the delivery dialer consult, so they cannot

internal/delivery/engine.go

@@ -14,6 +14,7 @@ import (
 	"go.uber.org/fx"
 	"gorm.io/gorm"
 	"sneak.berlin/go/webhooker/internal/database"
+	"sneak.berlin/go/webhooker/internal/globals"
 	"sneak.berlin/go/webhooker/internal/lifecycle"
 	"sneak.berlin/go/webhooker/internal/logger"
 	"sneak.berlin/go/webhooker/internal/metrics"
@@ -146,8 +147,10 @@ type EngineParams struct {
 
 	DB        *database.Database
 	DBManager *database.WebhookDBManager
+	Globals   *globals.Globals
 	Logger    *logger.Logger
 	SSRFGuard *Guard
+	Metrics   *metrics.Set
 }
 
 // Engine processes queued deliveries in the background
@@ -167,10 +170,14 @@ 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.
+	// version is the running build's version, the one the web UI
+	// footer shows. userAgent puts it on every outbound request.
+	version string
+
+	// mtr is the delivery metric set. Production wires the one
+	// registered on the registry /metrics serves; a test can
+	// substitute a set registered on a registry it holds, so it can
+	// gather what its own deliveries recorded.
 	mtr *metrics.Set
 
 	// targets maps each target type to its implementation.
@@ -204,7 +211,8 @@ func New(
 		deliveryCh: make(chan Task, deliveryChannelSize),
 		retryCh:    make(chan Task, retryChannelSize),
 		workers:    defaultWorkers,
-		mtr:        metrics.Default(),
+		version:    params.Globals.Version,
+		mtr:        params.Metrics,
 	}
 
 	e.initTargets(&http.Client{
@@ -300,6 +308,13 @@ func (e *Engine) ScheduleRetry(
 	})
 }
 
+// userAgent is the User-Agent header of every http and slack
+// delivery request: the program name and the running build's
+// version.
+func (e *Engine) userAgent() string {
+	return "webhooker/" + e.version
+}
+
 // registerHooks wires the engine's start and stop into the fx
 // lifecycle. The start hook's context is deliberately ignored
 // (see start for why the worker pool must not inherit it); the

internal/delivery/engine_test.go

@@ -1247,11 +1247,6 @@ func TestDoHTTPRequest_ForwardsHeaders(t *testing.T) {
 		testContentType,
 		receivedHeaders.Get("Content-Type"),
 	)
-
-	assert.Equal(t,
-		"webhooker/1.0",
-		receivedHeaders.Get("User-Agent"),
-	)
 }
 
 // The event's stored inbound headers carry the same Content-Type the
@@ -1320,6 +1315,7 @@ func TestApplyRequestHeaders_SendsOneContentType(t *testing.T) {
 					ContentType: tc.event,
 				},
 				cfg,
+				"webhooker/dev",
 			)
 
 			assert.Equal(t,

internal/delivery/export_test.go

@@ -9,6 +9,7 @@ import (
 	"net/url"
 	"time"
 
+	"github.com/prometheus/client_golang/prometheus"
 	"go.uber.org/fx"
 	"gorm.io/gorm"
 	"sneak.berlin/go/webhooker/internal/database"
@@ -82,8 +83,9 @@ func ExportApplyRequestHeaders(
 	req *http.Request,
 	event *database.Event,
 	cfg *HTTPTargetConfig,
+	userAgent string,
 ) []string {
-	return applyRequestHeaders(req, event, cfg)
+	return applyRequestHeaders(req, event, cfg, userAgent)
 }
 
 // ExportTruncate exposes truncate for testing.
@@ -399,7 +401,7 @@ func NewTestEngine(
 		deliveryCh: make(chan Task, deliveryChannelSize),
 		retryCh:    make(chan Task, retryChannelSize),
 		workers:    workers,
-		mtr:        metrics.Default(),
+		mtr:        metrics.New(prometheus.NewRegistry()),
 	}
 	e.initTargets(client)
 
@@ -414,7 +416,7 @@ func NewTestEngineSmallRetry(
 	e := &Engine{
 		log:     log,
 		retryCh: make(chan Task, 1),
-		mtr:     metrics.Default(),
+		mtr:     metrics.New(prometheus.NewRegistry()),
 	}
 	e.initTargets(nil)
 
@@ -437,7 +439,7 @@ func NewTestEngineWithDB(
 		deliveryCh: make(chan Task, deliveryChannelSize),
 		retryCh:    make(chan Task, retryChannelSize),
 		workers:    workers,
-		mtr:        metrics.Default(),
+		mtr:        metrics.New(prometheus.NewRegistry()),
 	}
 	e.initTargets(client)
 
@@ -445,8 +447,7 @@ func NewTestEngineWithDB(
 }
 
 // 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.
+// assert on collectors registered on a registry it holds.
 func (e *Engine) ExportSetMetrics(mtr *metrics.Set) {
 	e.mtr = mtr
 }

internal/delivery/metrics_test.go

@@ -35,9 +35,8 @@ const (
 )
 
 // 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.
+// registry this test holds, so its exact assertions can gather from
+// it.
 func mIsolate(
 	t *testing.T, s iSetup,
 ) *prometheus.Registry {

internal/delivery/redirect_test.go

@@ -375,6 +375,7 @@ func TestApplyRequestHeaders_ReportsOriginScopedNames(t *testing.T) {
 				"Content-Type":  testContentType,
 			},
 		},
+		"webhooker/dev",
 	)
 
 	assert.Equal(t,

internal/delivery/target_http.go

@@ -442,7 +442,9 @@ func (t *httpTarget) doHTTPRequest(
 		)
 	}
 
-	originScoped := applyRequestHeaders(req, event, cfg)
+	originScoped := applyRequestHeaders(
+		req, event, cfg, t.eng.userAgent(),
+	)
 
 	client := t.clientForRequest(cfg, originScoped)
 
@@ -562,10 +564,13 @@ func isForwardableHeader(name string) bool {
 // Content-Type goes out once: a Content-Type configured on the target
 // wins, otherwise the event's ContentType, otherwise none. The inbound
 // Content-Type in the event's headers is never forwarded.
+//
+// userAgent is set last, over any configured or inbound User-Agent.
 func applyRequestHeaders(
 	req *http.Request,
 	event *database.Event,
 	cfg *HTTPTargetConfig,
+	userAgent string,
 ) []string {
 	if event.ContentType != "" {
 		req.Header.Set(
@@ -580,7 +585,7 @@ func applyRequestHeaders(
 		originScoped[http.CanonicalHeaderKey(k)] = struct{}{}
 	}
 
-	req.Header.Set("User-Agent", "webhooker/1.0")
+	req.Header.Set("User-Agent", userAgent)
 
 	// A Content-Type configured on the target describes the body
 	// being sent rather than the sender. A 307/308 preserves the

internal/delivery/target_slack.go

@@ -136,7 +136,7 @@ func (t *slackTarget) attempt(
 	}
 
 	req.Header.Set("Content-Type", "application/json")
-	req.Header.Set("User-Agent", "webhooker/1.0")
+	req.Header.Set("User-Agent", t.eng.userAgent())
 
 	resp, doErr := executeHTTPRequest(t.client, req)
 	durationMs := time.Since(start).Milliseconds()

internal/delivery/user_agent_test.go

@@ -0,0 +1,91 @@
+package delivery_test
+
+import (
+	"context"
+	"encoding/json"
+	"net/http"
+	"net/http/httptest"
+	"net/netip"
+	"testing"
+
+	"github.com/google/uuid"
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"go.uber.org/fx/fxtest"
+	"sneak.berlin/go/webhooker/internal/database"
+	"sneak.berlin/go/webhooker/internal/delivery"
+	"sneak.berlin/go/webhooker/internal/globals"
+	"sneak.berlin/go/webhooker/internal/logger"
+	"sneak.berlin/go/webhooker/internal/metrics"
+)
+
+// Both the http and the slack target send webhooker/ and the version
+// in Globals, the value the web UI footer shows. A User-Agent
+// configured on the target or carried in by the sender does not
+// replace it.
+func TestUserAgent_IsTheBuildVersion(t *testing.T) {
+	t.Parallel()
+
+	const want = "webhooker/1.2.3-test"
+
+	userAgents := make(chan string, 1)
+
+	ts := httptest.NewServer(http.HandlerFunc(
+		func(w http.ResponseWriter, r *http.Request) {
+			userAgents <- r.Header.Get("User-Agent")
+
+			w.WriteHeader(http.StatusOK)
+		},
+	))
+	defer ts.Close()
+
+	g := &globals.Globals{Version: "1.2.3-test"}
+	lc := fxtest.NewLifecycle(t)
+
+	log, err := logger.New(lc, logger.LoggerParams{Globals: g})
+	require.NoError(t, err)
+
+	e := delivery.New(lc, delivery.EngineParams{
+		Globals: g,
+		Logger:  log,
+		// httptest listens on loopback, which the default guard
+		// refuses.
+		SSRFGuard: delivery.NewTestGuard(
+			netip.MustParsePrefix("127.0.0.0/8"),
+		),
+		Metrics: metrics.New(prometheus.NewRegistry()),
+	})
+
+	statusCode, _, _, err := e.ExportDoHTTPRequest(
+		context.Background(),
+		&delivery.HTTPTargetConfig{
+			URL:     ts.URL,
+			Headers: map[string]string{"User-Agent": "configured/1"},
+		},
+		&database.Event{Headers: `{"User-Agent":["curl/8"]}`},
+	)
+	require.NoError(t, err)
+	require.Equal(t, http.StatusOK, statusCode)
+	require.Len(t, userAgents, 1, "the http target sent no request")
+	assert.Equal(t, want, <-userAgents, "http target")
+
+	db := testWebhookDB(t)
+	targetID := uuid.New().String()
+
+	slackCfg, err := json.Marshal(
+		delivery.SlackTargetConfig{WebhookURL: ts.URL},
+	)
+	require.NoError(t, err)
+
+	event := seedEvent(t, db, `{"action":"test"}`)
+	dlv := seedDelivery(
+		t, db, event.ID, targetID, database.DeliveryStatusPending,
+	)
+
+	e.ExportDeliverSlack(context.Background(), db, buildSlackDelivery(
+		dlv, event, targetID, "test-slack", string(slackCfg),
+	))
+	require.Len(t, userAgents, 1, "the slack target sent no request")
+	assert.Equal(t, want, <-userAgents, "slack target")
+}

internal/handlers/handlers.go

@@ -12,6 +12,7 @@ import (
 	"net/http"
 	"sync/atomic"
 
+	"github.com/prometheus/client_golang/prometheus"
 	"go.uber.org/fx"
 	"sneak.berlin/go/webhooker/internal/database"
 	"sneak.berlin/go/webhooker/internal/delivery"
@@ -64,6 +65,8 @@ type HandlersParams struct {
 	Notifier     delivery.Notifier
 	Evictor      delivery.WebhookEvictor
 	SSRFGuard    *delivery.Guard
+	Metrics      *metrics.Set
+	Registry     *prometheus.Registry
 }
 
 // Handlers provides HTTP handler methods for all application
@@ -130,7 +133,7 @@ func New(
 	s.mw = params.Middleware
 	s.notifier = params.Notifier
 	s.evictor = params.Evictor
-	s.mtr = metrics.Default()
+	s.mtr = params.Metrics
 	s.ssrf = params.SSRFGuard
 
 	// Parse all page templates once at startup

internal/handlers/handlers_test.go

@@ -20,6 +20,7 @@ import (
 	"sneak.berlin/go/webhooker/internal/handlers"
 	"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"
 )
@@ -109,6 +110,8 @@ func newTestApp(
 			func(r *recordingEvictor) delivery.WebhookEvictor {
 				return r
 			},
+			metrics.NewRegistry,
+			metrics.New,
 			middleware.New,
 			delivery.NewGuard,
 			handlers.New,

internal/handlers/metrics.go

@@ -0,0 +1,21 @@
+package handlers
+
+import (
+	"net/http"
+
+	"github.com/prometheus/client_golang/prometheus/promhttp"
+)
+
+// HandleMetrics returns the Prometheus scrape handler for the
+// registry built by metrics.NewRegistry, which the HTTP, delivery, Go
+// runtime and process collectors register on. It is what
+// promhttp.Handler builds for the global default registry, including
+// the promhttp_metric_handler_* series that count scrapes, pointed at
+// that registry instead.
+func (s *Handlers) HandleMetrics() http.HandlerFunc {
+	reg := s.params.Registry
+
+	return promhttp.InstrumentMetricHandler(
+		reg, promhttp.HandlerFor(reg, promhttp.HandlerOpts{}),
+	).ServeHTTP
+}

internal/handlers/notice.go

@@ -13,8 +13,8 @@ const noticeParam = "notice"
 type noticeCode string
 
 // The codes of the actions on the webhook pages and of signing out.
-// Replay's and resubmit's are beside those actions, with the reasons
-// each can be refused.
+// Replay's codes, with the reasons a replay can be refused, and
+// resubmit's codes are defined beside those actions.
 const (
 	webhookCreated        noticeCode = "webhook-created"
 	webhookSaved          noticeCode = "webhook-saved"

internal/handlers/source_detail_test.go

@@ -241,3 +241,37 @@ func TestHandleSourceDetail_RendersNamedTargetFields(
 	assert.Contains(t, body, "(unavailable)")
 	assert.NotContains(t, body, "beak")
 }
+
+// TestHandleSourceDetail_FitsWideAndNarrowWindows pins the webhook
+// page's maximum width at 108rem (1728 px), half again the 72rem of
+// max-w-6xl that the webhook list and the event log use, so an
+// entrypoint URL fits on one line in a 1920-pixel window; and the
+// wrapping of its title row, so the buttons beside the title do not
+// push a phone-width window into scrolling sideways.
+func TestHandleSourceDetail_FitsWideAndNarrowWindows(t *testing.T) {
+	t.Parallel()
+
+	var (
+		h    *handlers.Handlers
+		sess *session.Session
+		db   *database.Database
+	)
+
+	app := newTestApp(t, &h, &sess, &db)
+	app.RequireStart()
+
+	t.Cleanup(app.RequireStop)
+
+	wh := seedWebhook(t, db)
+
+	body := renderSourceDetailPage(t, h, sess, wh.ID)
+
+	assert.Contains(
+		t, body,
+		`<div class="mx-auto px-6 py-8" style="max-width: 108rem"`,
+	)
+	assert.Contains(
+		t, body,
+		`<div class="flex flex-wrap justify-between items-center gap-2 mt-2">`,
+	)
+}

internal/metrics/metrics.go

@@ -3,17 +3,18 @@
 // 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.
+// It also builds the registry the authenticated /metrics route
+// serves. In production, these collectors, the inbound HTTP metrics
+// recorded in internal/middleware, and the Go runtime and process
+// collectors all register on that one registry, never on Prometheus's
+// global default.
 package metrics
 
 import (
-	"sync"
 	"time"
 
 	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/collectors"
 	"github.com/prometheus/client_golang/prometheus/promauto"
 	"sneak.berlin/go/webhooker/internal/database"
 )
@@ -57,25 +58,31 @@ var knownTargetTypes = []database.TargetType{
 	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.
+// NewRegistry returns the registry /metrics serves, carrying the Go
+// runtime and process collectors that Prometheus's global default
+// registry carries, so the go_* and process_* series stay in the
+// scrape.
 //
-//nolint:gochecknoglobals // one process-wide registration, by design
-var defaultSet = sync.OnceValue(func() *Set {
-	return New(prometheus.DefaultRegisterer)
-})
+// A registry of its own, rather than the global default, is what lets
+// two dependency graphs in one process — two tests, say — each
+// register their collectors without the second registration
+// panicking.
+func NewRegistry() *prometheus.Registry {
+	reg := prometheus.NewRegistry()
+	reg.MustRegister(
+		collectors.NewGoCollector(),
+		collectors.NewProcessCollector(
+			collectors.ProcessCollectorOpts{},
+		),
+	)
 
-// Default returns the process-wide metric set.
-func Default() *Set {
-	return defaultSet()
+	return reg
 }
 
 // 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.
+// Production builds one on the registry /metrics serves; tests build
+// one on a registry of their own so they can gather what their own
+// deliveries recorded.
 type Set struct {
 	eventsReceived      prometheus.Counter
 	deliveryAttempts    *prometheus.CounterVec
@@ -93,7 +100,7 @@ type Set struct {
 // 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 {
+func New(reg *prometheus.Registry) *Set {
 	factory := promauto.With(reg)
 
 	s := &Set{

internal/middleware/export_test.go

@@ -10,8 +10,7 @@ import (
 
 // MetricsMiddlewareForTest builds the metrics recording middleware
 // against a caller-supplied recorder, so a test can gather from its
-// own Prometheus registry rather than the process-wide default one
-// that Middleware.Metrics uses.
+// own Prometheus registry without building a whole Middleware.
 func MetricsMiddlewareForTest(
 	rec httpmetrics.Recorder,
 ) func(http.Handler) http.Handler {

internal/middleware/metrics.go

@@ -7,7 +7,6 @@ import (
 
 	"github.com/go-chi/chi"
 	httpmetrics "github.com/slok/go-http-metrics/metrics"
-	prommetrics "github.com/slok/go-http-metrics/metrics/prometheus"
 	ghmm "github.com/slok/go-http-metrics/middleware"
 	"github.com/slok/go-http-metrics/middleware/std"
 )
@@ -151,17 +150,17 @@ func (r boundedLabelRecorder) AddInflightRequests(
 
 var _ httpmetrics.Recorder = boundedLabelRecorder{}
 
-// Metrics returns middleware that records Prometheus HTTP metrics on
-// the default registry, which is the one the /metrics route gathers.
+// Metrics returns middleware that records Prometheus HTTP metrics
+// with the Middleware's one recorder, which New builds on the registry
+// the /metrics route serves and NewForTest on a registry of its own.
+// Every call reuses that recorder, so any number of routers can
+// install it.
 func (s *Middleware) Metrics() func(http.Handler) http.Handler {
-	return metricsMiddleware(
-		prommetrics.NewRecorder(prommetrics.Config{}),
-	)
+	return metricsMiddleware(s.metricsRecorder)
 }
 
 // metricsMiddleware builds the recording middleware against a given
-// recorder, so tests can gather from a registry of their own instead
-// of the process-wide default.
+// recorder, so tests can gather from a registry of their own.
 func metricsMiddleware(
 	rec httpmetrics.Recorder,
 ) func(http.Handler) http.Handler {

internal/middleware/metrics_test.go

@@ -57,9 +57,8 @@ const (
 // Server.setupWebhookRoutes inside it. That ordering is the whole
 // defect, so a test that flattens it would prove nothing.
 //
-// The recorder writes to a registry of the test's own rather than the
-// process-wide default one, so each test observes only its own
-// traffic.
+// The recorder writes to a registry of the test's own, so each test
+// observes only its own traffic.
 func metricsTestRouter(
 	t *testing.T,
 	receiverLimit int,
@@ -455,3 +454,29 @@ func TestMetrics_StatusAndSizeStillRecorded(t *testing.T) {
 		"the interceptor must still count written bytes",
 	)
 }
+
+// TestMetrics_WorksOnNewForTestMiddleware pins that a Middleware built
+// by NewForTest has a recorder of its own: its Metrics() serves a
+// request instead of panicking, and a second one does not collide
+// with the first.
+func TestMetrics_WorksOnNewForTestMiddleware(t *testing.T) {
+	t.Parallel()
+
+	log := slog.New(slog.DiscardHandler)
+	cfg := &config.Config{Environment: "prod"}
+	ok := http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
+		_, _ = w.Write([]byte(okBody))
+	})
+
+	for range 2 {
+		h := middleware.NewForTest(log, cfg, nil).Metrics()(ok)
+
+		req := httptest.NewRequestWithContext(
+			t.Context(), http.MethodGet, okRoute, nil,
+		)
+		w := httptest.NewRecorder()
+		h.ServeHTTP(w, req)
+
+		assert.Equal(t, http.StatusOK, w.Code)
+	}
+}

internal/middleware/middleware.go

@@ -14,6 +14,9 @@ import (
 	"github.com/go-chi/chi"
 	"github.com/go-chi/chi/middleware"
 	"github.com/go-chi/cors"
+	"github.com/prometheus/client_golang/prometheus"
+	httpmetrics "github.com/slok/go-http-metrics/metrics"
+	prommetrics "github.com/slok/go-http-metrics/metrics/prometheus"
 	"go.uber.org/fx"
 	"sneak.berlin/go/webhooker/internal/config"
 	"sneak.berlin/go/webhooker/internal/globals"
@@ -149,10 +152,11 @@ const (
 type MiddlewareParams struct {
 	fx.In
 
-	Logger  *logger.Logger
-	Globals *globals.Globals
-	Config  *config.Config
-	Session *session.Session
+	Logger   *logger.Logger
+	Globals  *globals.Globals
+	Config   *config.Config
+	Session  *session.Session
+	Registry *prometheus.Registry
 }
 
 // Middleware provides HTTP middleware for logging, CORS, auth, and
@@ -162,6 +166,14 @@ type Middleware struct {
 	params  *MiddlewareParams
 	session *session.Session
 
+	// metricsRecorder records the inbound HTTP metrics. New builds
+	// it on the registry /metrics serves, NewForTest on a registry
+	// of its own. Either way it is built once per Middleware and
+	// Metrics reuses it, because building it registers its
+	// collectors, and a second registration on the same registry
+	// panics.
+	metricsRecorder httpmetrics.Recorder
+
 	// loginGuard counts failed credential verifications and bounds
 	// concurrent password hashing. It is built on first use so that
 	// every construction path gets one; see guard().
@@ -180,6 +192,9 @@ func New(
 	s.params = &params
 	s.log = params.Logger.Get()
 	s.session = params.Session
+	s.metricsRecorder = prommetrics.NewRecorder(
+		prommetrics.Config{Registry: params.Registry},
+	)
 
 	return s, nil
 }

internal/middleware/testing.go

@@ -3,12 +3,17 @@ package middleware
 import (
 	"log/slog"
 
+	"github.com/prometheus/client_golang/prometheus"
+	prommetrics "github.com/slok/go-http-metrics/metrics/prometheus"
 	"sneak.berlin/go/webhooker/internal/config"
 	"sneak.berlin/go/webhooker/internal/session"
 )
 
 // NewForTest creates a Middleware with the minimum dependencies
 // needed for testing. This bypasses the fx lifecycle.
+//
+// Its metrics recorder writes to a fresh registry of its own, so
+// Metrics() works on it and two of them never collide.
 func NewForTest(
 	log *slog.Logger,
 	cfg *config.Config,
@@ -20,5 +25,8 @@ func NewForTest(
 			Config: cfg,
 		},
 		session: sess,
+		metricsRecorder: prommetrics.NewRecorder(
+			prommetrics.Config{Registry: prometheus.NewRegistry()},
+		),
 	}
 }

internal/resetpw/resetpw_test.go

@@ -24,6 +24,7 @@ import (
 	"sneak.berlin/go/webhooker/internal/handlers"
 	"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/resetpw"
 	"sneak.berlin/go/webhooker/internal/session"
@@ -163,6 +164,8 @@ func newServerApp(
 			session.New,
 			func() delivery.Notifier { return &noopNotifier{} },
 			func() delivery.WebhookEvictor { return &noopEvictor{} },
+			metrics.NewRegistry,
+			metrics.New,
 			middleware.New,
 			delivery.NewGuard,
 			handlers.New,

internal/server/routes.go

@@ -7,7 +7,6 @@ import (
 	sentryhttp "github.com/getsentry/sentry-go/http"
 	"github.com/go-chi/chi"
 	"github.com/go-chi/chi/middleware"
-	"github.com/prometheus/client_golang/prometheus/promhttp"
 	"sneak.berlin/go/webhooker/static"
 )
 
@@ -149,12 +148,7 @@ func (s *Server) setupRoutes() {
 	if s.params.Config.MetricsAuthEnabled() {
 		s.router.Group(func(r chi.Router) {
 			r.Use(s.mw.MetricsAuth())
-			r.Get(
-				"/metrics",
-				http.HandlerFunc(
-					promhttp.Handler().ServeHTTP,
-				),
-			)
+			r.Get("/metrics", s.h.HandleMetrics())
 		})
 	}
 

internal/server/routes_test.go

@@ -24,6 +24,7 @@ import (
 	"sneak.berlin/go/webhooker/internal/handlers"
 	"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/server"
 	"sneak.berlin/go/webhooker/internal/session"
@@ -113,6 +114,8 @@ func newTestEnvWithConfig(
 			session.New,
 			func() delivery.Notifier { return &noopNotifier{} },
 			func() delivery.WebhookEvictor { return &noopEvictor{} },
+			metrics.NewRegistry,
+			metrics.New,
 			middleware.New,
 			delivery.NewGuard,
 			handlers.New,
@@ -1530,3 +1533,46 @@ func TestMetricsRouteUnmountedOnHalfSetConfig(t *testing.T) {
 		})
 	}
 }
+
+// TestTwoMetricsRoutersInOneProcess pins
+// https://git.eeqj.de/sneak/webhooker/issues/227: a second
+// metrics-enabled router in one process used to panic, because the
+// HTTP metrics registered on Prometheus's global default registry.
+// Two routers are built over separate dependency graphs and a third
+// over the first graph again, and each must still serve the HTTP,
+// delivery, Go runtime and process series, and the series counting
+// scrapes of /metrics itself.
+func TestTwoMetricsRoutersInOneProcess(t *testing.T) {
+	t.Parallel()
+
+	first := newTestEnvWithConfig(
+		t, metricsConfig(t, metricsUser, metricsAuthValue),
+	)
+	second := newTestEnvWithConfig(
+		t, metricsConfig(t, metricsUser, metricsAuthValue),
+	)
+	third := &testEnv{
+		router: server.NewRouterForTest(
+			first.log.Get(), first.cfg, first.mw, first.hnd,
+		),
+	}
+
+	for _, env := range []*testEnv{first, second, third} {
+		env.get("/", nil)
+
+		scrape := env.metricsRequest(metricsUser, metricsAuthValue)
+		require.Equal(t, http.StatusOK, scrape.Code)
+
+		for _, series := range []string{
+			"http_request_duration_seconds",
+			"http_response_size_bytes",
+			"http_requests_inflight",
+			"webhooker_events_received_total",
+			"go_goroutines",
+			"process_start_time_seconds",
+			"promhttp_metric_handler_requests_total",
+		} {
+			assert.Contains(t, scrape.Body.String(), series)
+		}
+	}
+}

templates/source_detail.html

@@ -3,10 +3,14 @@
 {{define "title"}}{{.Webhook.Name}} - Webhooker{{end}}
 
 {{define "content"}}
-<div class="max-w-6xl mx-auto px-6 py-8" x-data="{ showAddEntrypoint: false, showAddTarget: false }">
+<!-- 108rem, half again the 72rem (max-w-6xl) of the webhook list, the
+     event log, the navbar and the footer, so an entrypoint URL fits on
+     one line. An inline style, because the committed tailwind.css has
+     no class this wide. -->
+<div class="mx-auto px-6 py-8" style="max-width: 108rem" x-data="{ showAddEntrypoint: false, showAddTarget: false }">
     <div class="mb-6">
         <a href="/hooks" class="text-sm text-primary-600 hover:text-primary-700">&larr; Back to webhooks</a>
-        <div class="flex justify-between items-center mt-2">
+        <div class="flex flex-wrap justify-between items-center gap-2 mt-2">
             <div>
                 <h1 class="text-2xl font-medium text-gray-900">{{.Webhook.Name}}</h1>
                 {{if .Webhook.Description}}