Log out with a form and count logouts instead of timing them (part of #256)

Logging out is now a POST in the CSRF-protected route group, sent by a
form on the generator page, so a link or image on another page of the
same site cannot end every login session. The session manager keeps a
count of logouts instead of the time of the latest one: each session
carries the count at its login and is refused once it has changed. No
clock is compared, so a login after a logout always works.

Model: opus-5-5

README.md

@@ -124,12 +124,8 @@ What the [upaas](https://git.eeqj.de/sneak/upaas) app for pixa needs:
       comma-separated; default none. Every image on a listed host is served to
       anyone without a signature, so list only hosts you control, where nobody
       else can put images.
-    - `PIXA_CACHE_MAX_BYTES`: disk cache limit in bytes; `0` disables it. Set
-      it: the volume is a directory on the host's filesystem, shared with the
-      host and every other app. The default is 75% of the sum of that
-      filesystem's free space and what the cache holds, and at least 500 MiB, so
-      the cache can grow to three quarters or more of the space they all have
-      left, and to all of it when that is 500 MiB or less.
+    - `PIXA_CACHE_MAX_BYTES`: disk cache limit in bytes; `0` disables it;
+      default 75% of (free space + what the cache holds)
     - the rest are in the table under Configuration below
 - **Health check:** the image's `HEALTHCHECK` requests
   `/.well-known/healthcheck.json`. upaas reads the container's health 60 seconds
@@ -656,10 +652,7 @@ See `configs/config.example.yml` for all options with defaults.
 - **Metrics**: Prometheus, at `/metrics`: generic HTTP request metrics
   (duration, response size, requests in flight) and the Go runtime and process
   metrics; requests are measured and `/metrics` is served only when
-  `metrics.username` and `metrics.password` are set. A request's `handler` label
-  is the pattern of the route it matches, such as `/v1/image/*`, never its path.
-  Requests that match no route share the label `unmatched`: those the router
-  answers 404 or 405, and CORS preflights
+  `metrics.username` and `metrics.password` are set
 - **Logging**: stdlib slog
 
 ## Entrypoints

TODO.md

@@ -30,22 +30,6 @@ P2: security: per-origin rate limiting
 
 # Completed Steps
 
-- 2026-10-15 "Running under upaas" in `README.md` tells the operator to set
-  `PIXA_CACHE_MAX_BYTES` (closes #251): it listed the variable as optional, but
-  under upaas the volume is a directory on the host's filesystem. The default,
-  75% of the sum of that filesystem's free space and what the cache holds, and
-  at least 500 MiB, let one pixa take three quarters or more of the space the
-  host and every other app had left, and all of it when that was 500 MiB or
-  less. The section now says so. The default is unchanged.
-- 2026-10-15 the request metrics are labelled by route, not by path (closes
-  #254): their `handler` label was each request's path, so every new path, a 404
-  or an encrypted URL, added series to the Prometheus registry that were never
-  removed, and `/metrics` listed every encrypted URL's token. The label is now
-  the pattern of the chi route the request matches, such as `/v1/image/*`, or
-  `unmatched` for a request that matches none: one the router answers 404 or
-  405, or a CORS preflight. The metrics library takes the label before the
-  request is routed, so the metrics middleware asks the router which route
-  matches.
 - 2026-10-15 logging out ends every login session (closes #256): a login session
   was a cookie with nothing kept on the server, so `/logout` removed it from one
   browser and a copy of it kept working for its 30 days. Every login is made

internal/middleware/middleware.go

@@ -8,15 +8,12 @@ import (
 	"net/http"
 	"net/netip"
 	"regexp"
-	"strings"
 	"time"
 
 	basicauth "github.com/99designs/basicauth-go"
-	"github.com/go-chi/chi/v5"
 	"github.com/go-chi/chi/v5/middleware"
 	"github.com/go-chi/cors"
 	"github.com/go-chi/httprate"
-	"github.com/prometheus/client_golang/prometheus"
 	metrics "github.com/slok/go-http-metrics/metrics/prometheus"
 	ghmm "github.com/slok/go-http-metrics/middleware"
 	"github.com/slok/go-http-metrics/middleware/std"
@@ -66,10 +63,6 @@ type Middleware struct {
 	log      *slog.Logger
 	config   *config.Config
 	clientIP *clientip.Resolver
-
-	// metricsRegistry is the registry Metrics registers its metrics with.
-	// nil is Prometheus' default registry, the one /metrics serves.
-	metricsRegistry prometheus.Registerer
 }
 
 // New creates a new Middleware instance.
@@ -216,65 +209,17 @@ func (s *Middleware) CORS() func(http.Handler) http.Handler {
 	})
 }
 
-// Metrics returns a Prometheus metrics middleware. Its handler label is the
-// pattern of the chi route a request matches, such as /v1/image/*, or
-// "unmatched" for a request that matches none, so the routes fix how many
-// values the label has. It is never the path, with which any client could
-// add series to the registry without limit.
+// Metrics returns a Prometheus metrics middleware.
 func (s *Middleware) Metrics() func(http.Handler) http.Handler {
 	mdlw := ghmm.New(ghmm.Config{
-		Recorder: metrics.NewRecorder(metrics.Config{
-			Registry: s.metricsRegistry,
-		}),
+		Recorder: metrics.NewRecorder(metrics.Config{}),
 	})
 
 	return func(next http.Handler) http.Handler {
-		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-			std.Handler(routePattern(r), mdlw, next).ServeHTTP(w, r)
-		})
+		return std.Handler("", mdlw, next)
 	}
 }
 
-// routePattern returns the pattern of the chi route r matches, or
-// "unmatched" when it matches none or is not served by a chi router. The
-// metrics library takes the label before the request is routed, so the
-// router is asked which route matches, with the path it routes on:
-// r.URL.RawPath when set, else r.URL.Path, else /.
-func routePattern(r *http.Request) string {
-	pattern := ""
-
-	rctx := chi.RouteContext(r.Context())
-	if rctx != nil {
-		path := r.URL.RawPath
-		if path == "" {
-			path = r.URL.Path
-		}
-
-		if path == "" {
-			path = "/"
-		}
-
-		pattern = rctx.Routes.Find(chi.NewRouteContext(), r.Method, path)
-
-		// For the path a subrouter is mounted at, such as /v1 or /v1/, Find
-		// answers that path without asking the subrouter, which chi hands
-		// the request as /.
-		for _, route := range rctx.Routes.Routes() {
-			if route.SubRoutes != nil &&
-				route.Pattern == strings.TrimSuffix(pattern, "/")+"/*" &&
-				!route.SubRoutes.Match(chi.NewRouteContext(), r.Method, "/") {
-				pattern = ""
-			}
-		}
-	}
-
-	if pattern == "" {
-		return "unmatched"
-	}
-
-	return pattern
-}
-
 // MetricsAuth returns a basic auth middleware for the metrics endpoint.
 func (s *Middleware) MetricsAuth() func(http.Handler) http.Handler {
 	return basicauth.New(

internal/middleware/middleware_internal_test.go

@@ -3,15 +3,12 @@ package middleware
 import (
 	"bytes"
 	"log/slog"
-	"maps"
 	"net/http"
 	"net/http/httptest"
 	"net/url"
 	"strings"
 	"testing"
 
-	"github.com/go-chi/chi/v5"
-	"github.com/prometheus/client_golang/prometheus"
 	"github.com/prometheus/client_golang/prometheus/promhttp"
 
 	"sneak.berlin/go/pixa/internal/config"
@@ -201,7 +198,7 @@ func TestMetricsRecordsServedRequest(t *testing.T) {
 
 	// The line /metrics shows once one GET /test has been served.
 	const want = `http_request_duration_seconds_count{` +
-		`code="200",handler="unmatched",method="GET",service=""} 1`
+		`code="200",handler="/test",method="GET",service=""} 1`
 
 	mw := &Middleware{log: slog.Default(), config: &config.Config{}}
 
@@ -223,97 +220,6 @@ func TestMetricsRecordsServedRequest(t *testing.T) {
 	}
 }
 
-// TestMetricsLabelsRequestsByRoute checks that the metrics middleware labels
-// each request with the pattern of the route that answers it, never with its
-// path: two paths one route answers share that route's pattern, and requests
-// no route answers, a 404 or a 405, share "unmatched", among them requests for
-// the path the subrouter is mounted at, /v1 and /v1/. A request with an empty
-// path is answered by the / route, as chi routes it as /, and is labelled /.
-// With a label per path, any client could add series to the registry without
-// limit. The middleware registers with a registry of its own here, as another
-// test in this package registers with Prometheus' default registry, which can
-// be done only once.
-func TestMetricsLabelsRequestsByRoute(t *testing.T) {
-	t.Parallel()
-
-	registry := prometheus.NewRegistry()
-	mw := &Middleware{
-		log:             slog.Default(),
-		config:          &config.Config{},
-		metricsRegistry: registry,
-	}
-
-	// The image route is in a subrouter, as in pixa's router.
-	router := chi.NewRouter()
-	router.Use(mw.Metrics())
-	router.Get("/", func(w http.ResponseWriter, _ *http.Request) {
-		w.WriteHeader(http.StatusOK)
-	})
-	router.Route("/v1", func(r chi.Router) {
-		r.Get("/image/*", func(w http.ResponseWriter, _ *http.Request) {
-			w.WriteHeader(http.StatusOK)
-		})
-	})
-
-	for _, req := range []struct{ method, path string }{
-		{http.MethodGet, "/v1/image/a.example.com/one.jpg/1x1.png"},
-		{http.MethodGet, "/v1/image/b.example.com/two.jpg/1x1.png"},
-		{http.MethodGet, "/no-such-route"},
-		{http.MethodGet, "/v1/no-such-route"},
-		{http.MethodGet, "/v1"},
-		{http.MethodGet, "/v1/"},
-		{http.MethodPost, "/v1/image/a.example.com/one.jpg/1x1.png"},
-		// The request line GET http://pixa.example HTTP/1.1 leaves both
-		// r.URL.Path and r.URL.RawPath empty.
-		{http.MethodGet, "http://pixa.example"},
-	} {
-		r := httptest.NewRequestWithContext(
-			t.Context(), req.method, req.path, nil)
-		t.Logf("%s %s: r.URL.Path %q, r.URL.RawPath %q",
-			req.method, req.path, r.URL.Path, r.URL.RawPath)
-		router.ServeHTTP(httptest.NewRecorder(), r)
-	}
-
-	got := requestCountsByHandler(t, registry)
-	t.Logf("requests counted by handler label: %v", got)
-
-	want := map[string]uint64{"/": 1, "/v1/image/*": 2, "unmatched": 5}
-	if !maps.Equal(got, want) {
-		t.Errorf("requests counted by handler label = %v, want %v", got, want)
-	}
-}
-
-// requestCountsByHandler returns how many requests the request duration
-// histogram in registry counted under each value of its handler label.
-func requestCountsByHandler(
-	t *testing.T, registry *prometheus.Registry,
-) map[string]uint64 {
-	t.Helper()
-
-	families, err := registry.Gather()
-	if err != nil {
-		t.Fatalf("registry.Gather() error = %v", err)
-	}
-
-	counts := map[string]uint64{}
-
-	for _, family := range families {
-		if family.GetName() != "http_request_duration_seconds" {
-			continue
-		}
-
-		for _, metric := range family.GetMetric() {
-			for _, label := range metric.GetLabel() {
-				if label.GetName() == "handler" {
-					counts[label.GetValue()] += metric.GetHistogram().GetSampleCount()
-				}
-			}
-		}
-	}
-
-	return counts
-}
-
 // TestLoggingLeavesOutSubmittedSigningKey checks that a login, a POST /
 // whose form carries the signing key, leaves no trace of the key in the
 // request's log line.

internal/server/logout_internal_test.go

@@ -4,7 +4,6 @@ import (
 	"net/http"
 	"net/http/httptest"
 	"net/url"
-	"path/filepath"
 	"regexp"
 	"strings"
 	"testing"
@@ -231,39 +230,3 @@ func TestLogoutOutlastsRestart(t *testing.T) {
 			"still opens the generator page")
 	}
 }
-
-// TestLostStateDirectoryEndsEveryLoginSession verifies that a pixa started on
-// an empty state directory, as pixad is after a restart that lost its state
-// directory, refuses a session cookie from before, and that a login on it
-// opens the generator page.
-func TestLostStateDirectoryEndsEveryLoginSession(t *testing.T) {
-	t.Parallel()
-
-	s := newTestServer(t)
-
-	before := logIn(t, s)
-	if !opensGeneratorPage(t, s, before) {
-		t.Fatal("logging in did not open the generator page")
-	}
-
-	emptyStateDir := *s.config
-	emptyStateDir.StateDir = t.TempDir()
-	emptyStateDir.DBURL = "file:" +
-		filepath.Join(emptyStateDir.StateDir, "state.sqlite3")
-
-	restarted := startPixa(t, &emptyStateDir)
-
-	opens := opensGeneratorPage(t, restarted, before)
-	t.Logf("on an empty state directory, the cookie from before opens the "+
-		"generator page: %v", opens)
-
-	if opens {
-		t.Error("on an empty state directory, a cookie from before still " +
-			"opens the generator page")
-	}
-
-	if !opensGeneratorPage(t, restarted, logIn(t, restarted)) {
-		t.Error("a login on an empty state directory does not open the " +
-			"generator page")
-	}
-}