Latency statistics written once, thresholds read from CONFIG (closes #102)

A target's min, max, median and average latency now come from one list
of its answers, through latencyStats(), which the summary's figures use
too, so the median is written once. latencyHex() and latencyClass() read
one table of color limits in CONFIG. The health thresholds, the debug
log's length, the gateway check's timeout, the recovery probe's number
of hosts and interval, how often the rows are sorted and the delay
before the first sparkline resize are CONFIG entries, read where the
numbers were. minLatency() and its three siblings stay for the unit
tests. Nothing the page does or shows changes. A unit test now covers
the summary's figures.

Model: opus-5-5

README.md

@@ -266,10 +266,6 @@ What the [upaas](https://git.eeqj.de/sneak/upaas) app for netwatch needs:
       password as their basic auth credentials. With neither set, there are no
       metrics and `/metrics` is not found. One set without the other, or a user
       name containing `:`, stops the container
-    - `SENTRY_DSN`, default empty: set to a Sentry project's DSN, the backend
-      sends its errors to that Sentry project: each request whose handling
-      crashes, which still gets a 500 response. A value Sentry does not accept
-      stops the container. Empty, the backend sends nothing to Sentry
 - **Health check:** the image's `HEALTHCHECK` requests
   `/.well-known/healthcheck` through nginx every 30 seconds, so it fails unless
   both nginx and the backend answer. upaas reads the container's health 60

TODO.md

@@ -33,14 +33,6 @@ latest run passes.
   `CONFIG` entries too. A unit test checks the summary's figures. Nothing the
   page does or shows changed; the footer's color legend still writes the limits
   out as text
-- 2026-10-04: the backend reports errors to Sentry (issue #95). With
-  `SENTRY_DSN` set, it sets up `sentry-go` with the release `netwatch-server-`
-  and its version, reports each panic in a handler through `sentryhttp`, the
-  last of the middleware every request goes through, which panics again so the
-  request still gets the 500 from the panic recovery, and waits up to 2 seconds
-  on shutdown for Sentry to finish sending. A DSN Sentry refuses stops the start
-  with an error naming `SENTRY_DSN`. With it empty, Sentry is not set up and
-  nothing is sent to it
 - 2026-10-04: a target's name and URL and a debug log message show as the
   characters they are and are never read as HTML (issue #29): a host row escapes
   the name and URL it writes into its markup, and the debug log sets each line

backend/README.md

@@ -90,7 +90,6 @@ project layout:
 | `CORS_ALLOWED_ORIGINS` | empty                | Comma-separated origins whose pages may call the API; see [CORS](#cors)                                  |
 | `METRICS_USERNAME`     | empty                | Basic auth user name for `/metrics`; see [Metrics](#metrics)                                             |
 | `METRICS_PASSWORD`     | empty                | Basic auth password for `/metrics`; see [Metrics](#metrics)                                              |
-| `SENTRY_DSN`           | empty                | DSN of the Sentry project to send errors to; see [Sentry](#sentry)                                       |
 
 `TRUSTED_PROXIES` defaults to
 `127.0.0.1/32,::1/128,10.0.0.0/8,172.16.0.0/12,192.168.0.0/16`. The loopback
@@ -199,16 +198,6 @@ is recorded and `/metrics` answers 404. One without the other stops the server
 from starting, with an error naming both; so does a `METRICS_USERNAME`
 containing `:`, which basic auth cannot carry, with an error naming it.
 
-### Sentry
-
-With `SENTRY_DSN` set, the server sends its errors to that Sentry project: each
-panic in a handler is reported there, under the release `netwatch-server-`
-followed by the server's version, and the request still gets 500 from the
-server's panic recovery. On shutdown the server waits up to 2 seconds for Sentry
-to finish sending. A DSN Sentry refuses stops the server from starting, with an
-error naming `SENTRY_DSN`. With it empty, Sentry is not set up, and nothing is
-sent to it.
-
 ## TODO
 
 - Add integration test that POSTs a report and verifies the compressed output

backend/cmd/netwatch-server/main_test.go

@@ -115,28 +115,6 @@ func TestMalformedConfigFileStopsTheStart(t *testing.T) {
 	}
 }
 
-// TestRefusedSentryDSNStopsTheStart: a SENTRY_DSN that Sentry refuses
-// stops the start, and the error, naming SENTRY_DSN, is logged as JSON.
-func TestRefusedSentryDSNStopsTheStart(t *testing.T) {
-	t.Setenv("SENTRY_DSN", "not-a-dsn")
-
-	ctx, cancel := context.WithTimeout(t.Context(), childTimeout)
-	defer cancel()
-
-	child, stdout, stderr := startServer(ctx, t, t.TempDir(), freePort(ctx, t))
-
-	err := child.Wait()
-	if child.ProcessState.ExitCode() != 1 {
-		t.Fatalf("server exit = %v, want exit status 1", err)
-	}
-
-	requireJSONLines(t, stdout, stderr)
-
-	if !strings.Contains(stdout.String(), "SENTRY_DSN") {
-		t.Fatalf("no error naming SENTRY_DSN in stdout:\n%s", stdout)
-	}
-}
-
 // startServer runs main() in a child process listening on
 // 127.0.0.1:port, with home as its HOME and working directory and its
 // data directory in home, so it touches nothing outside home. Its

backend/go.mod

@@ -4,7 +4,6 @@ go 1.25.5
 
 require (
 	github.com/99designs/basicauth-go v0.0.0-20230316000542-bf6f9cbbf0f8
-	github.com/getsentry/sentry-go v0.49.0
 	github.com/go-chi/chi/v5 v5.2.5
 	github.com/go-chi/cors v1.2.2
 	github.com/go-chi/httprate v0.16.0

backend/go.sum

@@ -4,22 +4,18 @@ github.com/beorn7/perks v1.0.1 h1:VlbKKnNfV8bJzeqoa4cOKqO6bYr3WgKZxO8Z16+hsOM=
 github.com/beorn7/perks v1.0.1/go.mod h1:G2ZrVWU2WbWT9wwq4/hrbKbnv/1ERSJQ0ibhJ6rlkpw=
 github.com/cespare/xxhash/v2 v2.3.0 h1:UL815xU9SqsFlibzuggzjXhog7bL6oX9BbNZnL2UFvs=
 github.com/cespare/xxhash/v2 v2.3.0/go.mod h1:VGX0DQ3Q6kWi7AoAeZDth3/j3BFtOZR5XLFGgcrjCOs=
-github.com/davecgh/go-spew v1.1.2-0.20180830191138-d8f796af33cc h1:U9qPSI2PIWSS1VwoXQT9A3Wy9MM3WgvqSxFWenqJduM=
+github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
-github.com/davecgh/go-spew v1.1.2-0.20180830191138-d8f796af33cc/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/frankban/quicktest v1.14.6 h1:7Xjx+VpznH+oBnejlPUj8oUpdxnVs4f8XU8WnHkI4W8=
 github.com/frankban/quicktest v1.14.6/go.mod h1:4ptaffx2x8+WTWXmUCuVU6aPUX1/Mz7zb5vbUoiM6w0=
 github.com/fsnotify/fsnotify v1.9.0 h1:2Ml+OJNzbYCTzsxtv8vKSFD9PbJjmhYF14k/jKC7S9k=
 github.com/fsnotify/fsnotify v1.9.0/go.mod h1:8jBTzvmWwFyi3Pb8djgCCO5IBqzKJ/Jwo8TRcHyHii0=
-github.com/getsentry/sentry-go v0.49.0 h1:Ehejknu1l023Ub7QoRBVLAI7g3Jnhqku4oWx4B4Sh5s=
-github.com/getsentry/sentry-go v0.49.0/go.mod h1:nuMJAoCfe1u0Bts2ocyNI+TW8HT84vRMqwA5Qq/SKUI=
 github.com/go-chi/chi/v5 v5.2.5 h1:Eg4myHZBjyvJmAFjFvWgrqDTXFyOzjj7YIm3L3mu6Ug=
 github.com/go-chi/chi/v5 v5.2.5/go.mod h1:X7Gx4mteadT3eDOMTsXzmI4/rwUpOwBHLpAfupzFJP0=
 github.com/go-chi/cors v1.2.2 h1:Jmey33TE+b+rB7fT8MUy1u0I4L+NARQlK6LhzKPSyQE=
 github.com/go-chi/cors v1.2.2/go.mod h1:sSbTewc+6wYHBBCW7ytsFSn836hqM7JxpglAy2Vzc58=
 github.com/go-chi/httprate v0.16.0 h1:8V5DH9j6pSK6UQoBsTpvMyFxycqaKEIToyPKzHJjUa8=
 github.com/go-chi/httprate v0.16.0/go.mod h1:A8lo+qRhk+s9LiuP5saS7XCGDXRXMcrueq0NfIuCa/I=
-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/go-viper/mapstructure/v2 v2.4.0 h1:EBsztssimR/CONLSZZ04E8qAkxNYq4Qp9LvH92wZUgs=
 github.com/go-viper/mapstructure/v2 v2.4.0/go.mod h1:oJDH3BJKyqBA2TXFhDsKDGDTlndYOZ6rGS0BRZIxGhM=
 github.com/google/go-cmp v0.7.0 h1:wk8382ETsv4JYUZwIsn6YpYiWiBsYLSJiTsyBybVuN8=
@@ -40,12 +36,8 @@ github.com/munnerz/goautoneg v0.0.0-20191010083416-a7dc8b61c822 h1:C3w9PqII01/Oq
 github.com/munnerz/goautoneg v0.0.0-20191010083416-a7dc8b61c822/go.mod h1:+n7T8mK8HuQTcFwEeznm/DIxMOiR9yIdICNftLE1DvQ=
 github.com/pelletier/go-toml/v2 v2.2.4 h1:mye9XuhQ6gvn5h28+VilKrrPoQVanw5PMw/TB0t5Ec4=
 github.com/pelletier/go-toml/v2 v2.2.4/go.mod h1:2gIqNv+qfxSVS7cM2xJQKtLSTLUE9V8t9Stt+h56mCY=
-github.com/pingcap/errors v0.11.4 h1:lFuQV/oaUMGcD2tqt+01ROSmJs75VG1ToEOkZIZ4nE4=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
-github.com/pingcap/errors v0.11.4/go.mod h1:Oi8TUi2kEtXXLMJk9l1cGmz20kV3TaQ0usTwv5KuLY8=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
-github.com/pkg/errors v0.9.1 h1:FEBLx1zS214owpjy7qsBeixbURkuhQAwrK5UwLGTwt4=
-github.com/pkg/errors v0.9.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
-github.com/pmezard/go-difflib v1.0.1-0.20181226105442-5d4384ee4fb2 h1:Jamvg5psRIccs7FGNTlIRMkT8wgtp5eCXdBlqhYGL6U=
-github.com/pmezard/go-difflib v1.0.1-0.20181226105442-5d4384ee4fb2/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 github.com/prometheus/client_golang v1.24.1 h1:JnJkREXzWxUdCuPFpIWZiPispT9xVV59uiuyR2bPlnU=
 github.com/prometheus/client_golang v1.24.1/go.mod h1:F+oSRECHg4sse5ucfYpYDeIv/hu68Zo0uoHKetWnzcE=
 github.com/prometheus/client_model v0.6.2 h1:oBsgwpGs7iVziMvrGhE53c/GrLUsZdHnqNwqPLxwZyk=
@@ -54,8 +46,8 @@ github.com/prometheus/common v0.70.1 h1:1HvjP4D5oL3t8RsPlwxA9onvvStjtIHYE5XuuwOi
 github.com/prometheus/common v0.70.1/go.mod h1:VdFUQDMZK3VLkurFUVhia6uys/0suUp86TJz5qbJRhc=
 github.com/prometheus/procfs v0.21.1 h1:GljZCt+zSTS+NZq88cyQ1LjZ+RCHp3uVuabBWA5+OJI=
 github.com/prometheus/procfs v0.21.1/go.mod h1:aB55Cww9pdSJVHk0hUf0inxWyyjPogFIjmHKYgMKmtY=
-github.com/rogpeppe/go-internal v1.14.1 h1:UQB4HGPB6osV0SQTLymcB4TgvyWu6ZyliaW0tI/otEQ=
+github.com/rogpeppe/go-internal v1.9.0 h1:73kH8U+JUqXU8lRuOHeVHaa/SZPifC7BkcraZVejAe8=
-github.com/rogpeppe/go-internal v1.14.1/go.mod h1:MaRKkUm5W0goXpeCfT7UZI6fk/L7L7so1lCWt35ZSgc=
+github.com/rogpeppe/go-internal v1.9.0/go.mod h1:WtVeX8xhTBvf0smdhujwtBcq4Qrzq/fJaraNFVN+nFs=
 github.com/sagikazarmark/locafero v0.11.0 h1:1iurJgmM9G3PA/I+wWYIOw/5SyBtxapeHDcg+AAIFXc=
 github.com/sagikazarmark/locafero v0.11.0/go.mod h1:nVIGvgyzw595SUSUE6tvCp3YYTeHs15MvlmU87WwIik=
 github.com/slok/go-http-metrics v0.13.0 h1:lQDyJJx9wKhmbliyUsZ2l6peGnXRHjsjoqPt5VYzcP8=
@@ -101,7 +93,7 @@ golang.org/x/text v0.40.0/go.mod h1:hpnzDAfGV753zIKo+wk3u1bVKCGPbrnF7+7LBF/UHVY=
 google.golang.org/protobuf v1.36.11 h1:fV6ZwhNocDyBLK0dj+fg8ektcVegBBuEolpbTQyBNVE=
 google.golang.org/protobuf v1.36.11/go.mod h1:HTf+CrKn2C3g5S8VImy6tdcUvCska2kB7j23XfzDpco=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
-gopkg.in/check.v1 v1.0.0-20201130134442-10cb98267c6c h1:Hei/4ADfdWqJk1ZMxUNpqntNwaWcugrBjAiHlqqRiVk=
+gopkg.in/check.v1 v1.0.0-20190902080502-41f04d3bba15 h1:YR8cESwS4TdDjEe65xsg0ogRM/Nc3DYOhEAlW+xobZo=
-gopkg.in/check.v1 v1.0.0-20201130134442-10cb98267c6c/go.mod h1:JHkPIbrfpd72SG/EVd6muEfDQjcINNoR0C8j2r3qZ4Q=
+gopkg.in/check.v1 v1.0.0-20190902080502-41f04d3bba15/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
 gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

backend/internal/server/export_test.go

@@ -1,13 +1,5 @@
 package server
 
-import "github.com/go-chi/chi/v5"
-
-// Router exposes the router to the external tests, which add routes
-// of their own to it after SetupRoutes.
-func (s *Server) Router() *chi.Mux {
-	return s.router
-}
-
 // MaxRequestBodyBytes exposes the router-wide body limit to the
 // external tests.
 const MaxRequestBodyBytes = maxRequestBodyBytes

backend/internal/server/routes.go

@@ -3,7 +3,6 @@ package server
 import (
 	"time"
 
-	sentryhttp "github.com/getsentry/sentry-go/http"
 	"github.com/go-chi/chi/v5"
 	"github.com/go-chi/chi/v5/middleware"
 	"github.com/prometheus/client_golang/prometheus"
@@ -33,12 +32,6 @@ func (s *Server) SetupRoutes() {
 	s.router.Use(s.mw.MaxBodyBytes(maxRequestBodyBytes))
 	s.router.Use(middleware.Timeout(requestTimeout))
 
-	// Sentry reports a panic, then panics again, so that s.mw.Recoverer
-	// still answers 500.
-	if s.params.Config.SentryDSN != "" {
-		s.router.Use(sentryhttp.New(sentryhttp.Options{Repanic: true}).Handle)
-	}
-
 	// The metrics go in a registry of this server's own, not in
 	// Prometheus' default one, which takes them only once per process.
 	registry := prometheus.NewRegistry()

backend/internal/server/routes_test.go

@@ -1,12 +1,10 @@
 package server_test
 
 import (
-	"io"
 	"net/http"
 	"net/http/httptest"
 	"strings"
 	"testing"
-	"time"
 
 	"sneak.berlin/go/netwatch/internal/config"
 	"sneak.berlin/go/netwatch/internal/globals"
@@ -17,7 +15,6 @@ import (
 	"sneak.berlin/go/netwatch/internal/reportbuf"
 	"sneak.berlin/go/netwatch/internal/server"
 
-	"github.com/getsentry/sentry-go"
 	"go.uber.org/fx"
 	"go.uber.org/fx/fxtest"
 )
@@ -199,70 +196,6 @@ func TestMetricsInTwoServers(t *testing.T) {
 	}
 }
 
-// TestSentry: with SENTRY_DSN empty there is no Sentry client. With it
-// pointing at a local server standing in for Sentry, a panic in a
-// handler reaches that server, and the request still gets the 500 from
-// the panic recovery.
-func TestSentry(t *testing.T) {
-	const panicMessage = "handler panic for TestSentry"
-
-	// sentry.Init sets the client for the whole process; take it away
-	// again so that no other test reports to Sentry.
-	t.Cleanup(func() { sentry.CurrentHub().BindClient(nil) })
-
-	t.Setenv("SENTRY_DSN", "")
-	newServer(t)
-
-	if sentry.CurrentHub().Client() != nil {
-		t.Fatal("a Sentry client exists with SENTRY_DSN empty")
-	}
-
-	// The body of the first request the stand-in for Sentry receives.
-	received := make(chan string, 1)
-
-	sentryServer := httptest.NewServer(http.HandlerFunc(
-		func(_ http.ResponseWriter, r *http.Request) {
-			body, _ := io.ReadAll(r.Body)
-
-			select {
-			case received <- string(body):
-			default:
-			}
-		},
-	))
-	defer sentryServer.Close()
-
-	t.Setenv("SENTRY_DSN",
-		"http://key@"+sentryServer.Listener.Addr().String()+"/1")
-
-	srv := newServer(t)
-	srv.SetupRoutes()
-	srv.Router().Get("/panic", func(http.ResponseWriter, *http.Request) {
-		panic(panicMessage)
-	})
-
-	rec := httptest.NewRecorder()
-	req := httptest.NewRequestWithContext(t.Context(),
-		http.MethodGet, "/panic", http.NoBody)
-	srv.ServeHTTP(rec, req)
-
-	if rec.Code != http.StatusInternalServerError {
-		t.Fatalf("status = %d, want %d",
-			rec.Code, http.StatusInternalServerError)
-	}
-
-	// Sentry sends from a goroutine of its own.
-	select {
-	case body := <-received:
-		if !strings.Contains(body, panicMessage) {
-			t.Fatalf("the Sentry server received no report of the panic:\n%s",
-				body)
-		}
-	case <-time.After(5 * time.Second):
-		t.Fatal("nothing reached the Sentry server")
-	}
-}
-
 // TestHealthCheckRejectsOversizeBody sends the health check, which
 // never reads its body, a body one byte over the limit. Only the
 // router-wide body limit can reject it.

backend/internal/server/server.go

@@ -7,10 +7,8 @@ package server
 
 import (
 	"context"
-	"fmt"
 	"log/slog"
 	"net/http"
-	"time"
 
 	"sneak.berlin/go/netwatch/internal/config"
 	"sneak.berlin/go/netwatch/internal/globals"
@@ -18,15 +16,10 @@ import (
 	"sneak.berlin/go/netwatch/internal/logger"
 	"sneak.berlin/go/netwatch/internal/middleware"
 
-	"github.com/getsentry/sentry-go"
 	"github.com/go-chi/chi/v5"
 	"go.uber.org/fx"
 )
 
-// sentryFlushTimeout is how long shutdown waits for Sentry to send
-// what it still holds.
-const sentryFlushTimeout = 2 * time.Second
-
 // Params defines the dependencies for Server.
 type Params struct {
 	fx.In
@@ -63,11 +56,6 @@ func New(
 	s.log = params.Logger.Get()
 	s.shutdowner = params.Shutdowner
 
-	err := s.enableSentry()
-	if err != nil {
-		return nil, err
-	}
-
 	lc.Append(fx.Hook{
 		OnStart: func(_ context.Context) error {
 			// Build the router and http.Server synchronously
@@ -99,37 +87,10 @@ func (s *Server) ServeHTTP(
 	s.router.ServeHTTP(w, r)
 }
 
-// enableSentry sets Sentry up when SENTRY_DSN is set, so that
-// SetupRoutes can report panics to it. With SENTRY_DSN empty it does
-// nothing. A DSN Sentry refuses stops the start.
-func (s *Server) enableSentry() error {
-	if s.params.Config.SentryDSN == "" {
-		return nil
-	}
-
-	err := sentry.Init(sentry.ClientOptions{
-		Dsn:     s.params.Config.SentryDSN,
-		Release: s.params.Globals.Appname + "-" + s.params.Globals.Version,
-	})
-	if err != nil {
-		return fmt.Errorf("SENTRY_DSN: %w", err)
-	}
-
-	s.log.Info("sentry error reporting activated")
-
-	return nil
-}
-
 // shutdown gracefully stops the HTTP server within the
-// deadline of the context fx provides for OnStop, then gives
+// deadline of the context fx provides for OnStop.
-// Sentry, if set up, time to send what it still holds.
 func (s *Server) shutdown(ctx context.Context) error {
 	err := s.httpServer.Shutdown(ctx)
-
-	if s.params.Config.SentryDSN != "" {
-		sentry.Flush(sentryFlushTimeout)
-	}
-
 	if err != nil {
 		s.log.Error("server clean shutdown failed", "error", err)
 

src/main.js

@@ -289,7 +289,8 @@ export class HostState {
     }
 
     // The min, max, median and average latency of the checks in the history
-    // that got an answer.
+    // that got an answer. updateHostRow reads all four from one call; the
+    // methods below each return one of them.
     historyStats() {
         return latencyStats(
             this.history
@@ -298,6 +299,22 @@ export class HostState {
         );
     }
 
+    averageLatency() {
+        return this.historyStats().avg;
+    }
+
+    minLatency() {
+        return this.historyStats().min;
+    }
+
+    maxLatency() {
+        return this.historyStats().max;
+    }
+
+    medianLatency() {
+        return this.historyStats().med;
+    }
+
     _trim() {
         while (this.history.length > CONFIG.maxHistoryPoints)
             this.history.shift();

test/unit/main.test.js

@@ -347,8 +347,16 @@ for (const { history, latencies, statistics } of [
     },
 ]) {
     test(`a target's min, max, average and median latency over ${history}`, () => {
-        const { min, max, avg, med } = hostAfter(latencies).historyStats();
+        const host = hostAfter(latencies);
-        assert.deepEqual({ min, max, average: avg, median: med }, statistics);
+        assert.deepEqual(
+            {
+                min: host.minLatency(),
+                max: host.maxLatency(),
+                average: host.averageLatency(),
+                median: host.medianLatency(),
+            },
+            statistics,
+        );
     });
 }