Wrap capture for services used by pieces of middleware

integration/access_log_test.go

@@ -606,10 +606,8 @@ func (s *AccessLogSuite) TestAccessLogPreflightHeadersMiddleware() {
 func (s *AccessLogSuite) TestAccessLogDisabledForInternals() {
 	ensureWorkingDirectoryIsClean()
 
-	file := s.adaptFile("fixtures/access_log/access_log_ping.toml", struct{}{})
-
 	// Start Traefik.
-	s.traefikCmd(withConfigFile(file))
+	s.traefikCmd(withConfigFile("fixtures/access_log/access_log_base.toml"))
 
 	defer func() {
 		traefikLog, err := os.ReadFile(traefikTestLogFile)
@@ -619,7 +617,7 @@ func (s *AccessLogSuite) TestAccessLogDisabledForInternals() {
 
 	// waitForTraefik makes at least one call to the rawdata api endpoint,
 	// but the logs for this endpoint are ignored in checkAccessLogOutput.
-	s.waitForTraefik("customPing")
+	s.waitForTraefik("service3")
 
 	s.checkStatsForLogFile()
 
@@ -636,8 +634,9 @@ func (s *AccessLogSuite) TestAccessLogDisabledForInternals() {
 	require.NoError(s.T(), err)
 
 	// Make some requests on the custom ping router.
-	req, err = http.NewRequest(http.MethodGet, "http://127.0.0.1:8000/ping", nil)
+	req, err = http.NewRequest(http.MethodGet, "http://127.0.0.1:8010/ping", nil)
 	require.NoError(s.T(), err)
+	req.Host = "ping.docker.local"
 
 	err = try.Request(req, 500*time.Millisecond, try.StatusCodeIs(http.StatusOK), try.HasBody())
 	require.NoError(s.T(), err)
@@ -649,6 +648,25 @@ func (s *AccessLogSuite) TestAccessLogDisabledForInternals() {
 
 	require.Equal(s.T(), 0, count)
 
+	// Make some requests on the custom ping router in error.
+	req, err = http.NewRequest(http.MethodGet, "http://127.0.0.1:8010/ping-error", nil)
+	require.NoError(s.T(), err)
+	req.Host = "ping-error.docker.local"
+
+	err = try.Request(req, 500*time.Millisecond, try.StatusCodeIs(http.StatusUnauthorized), try.BodyContains("X-Forwarded-Host: ping-error.docker.local"))
+	require.NoError(s.T(), err)
+	err = try.Request(req, 500*time.Millisecond, try.StatusCodeIs(http.StatusUnauthorized), try.BodyContains("X-Forwarded-Host: ping-error.docker.local"))
+	require.NoError(s.T(), err)
+
+	// Here we verify that the remove of observability doesn't break the metrics for the error page service.
+	req, err = http.NewRequest(http.MethodGet, "http://127.0.0.1:8080/metrics", nil)
+	require.NoError(s.T(), err)
+
+	err = try.Request(req, 500*time.Millisecond, try.StatusCodeIs(http.StatusOK), try.BodyContains("service3"))
+	require.NoError(s.T(), err)
+	err = try.Request(req, 500*time.Millisecond, try.StatusCodeIs(http.StatusOK), try.BodyNotContains("service=\"ping"))
+	require.NoError(s.T(), err)
+
 	// Verify no other Traefik problems.
 	s.checkNoOtherTraefikProblems()
 }

integration/fixtures/access_log/access_log_base.toml

@@ -22,10 +22,17 @@
     address = ":8008"
   [entryPoints.preflight]
     address = ":8009"
+  [entryPoints.ping]
+    address = ":8010"
 
 [api]
   insecure = true
 
+[ping]
+
+[metrics]
+  [metrics.prometheus]
+
 [providers]
   [providers.docker]
     exposedByDefault = false

integration/fixtures/access_log/access_log_ping.toml

@@ -1,30 +0,0 @@
-[global]
-  checkNewVersion = false
-  sendAnonymousUsage = false
-
-[log]
-  level = "ERROR"
-  filePath = "traefik.log"
-
-[accessLog]
-  filePath = "access.log"
-
-[entryPoints]
-  [entryPoints.web]
-    address = ":8000"
-
-[api]
-  insecure = true
-
-[ping]
-
-[providers]
-  [providers.file]
-    filename = "{{ .SelfFilename }}"
-
-## dynamic configuration ##
-[http.routers]
-  [http.routers.customPing]
-    entryPoints = ["web"]
-    rule = "PathPrefix(`/ping`)"
-    service = "ping@internal"

integration/resources/compose/access_log.yml

@@ -94,3 +94,21 @@ services:
       traefik.http.routers.rt-preflightCORS.middlewares: preflightCORS
       traefik.http.middlewares.preflightCORS.headers.accessControlAllowMethods: OPTIONS, GET
       traefik.http.services.preflightCORS.loadbalancer.server.port: 80
+
+  ping:
+    image: traefik/whoami
+    labels:
+      traefik.enable: true
+      traefik.http.routers.ping.entryPoints: ping
+      traefik.http.routers.ping.rule: PathPrefix(`/ping`)
+      traefik.http.routers.ping.service: ping@internal
+
+      traefik.http.routers.ping-error.entryPoints: ping
+      traefik.http.routers.ping-error.rule: PathPrefix(`/ping-error`)
+      traefik.http.routers.ping-error.middlewares: errors, basicauth
+      traefik.http.routers.ping-error.service: ping@internal
+      traefik.http.middlewares.basicauth.basicauth.users: "test:$apr1$H6uskkkW$IgXLP6ewTrSuBkTrqE8wj/"
+      traefik.http.middlewares.errors.errors.status: 401
+      traefik.http.middlewares.errors.errors.service: service3
+      traefik.http.middlewares.errors.errors.query: /
+      traefik.http.services.service3.loadbalancer.server.port: 80

pkg/middlewares/capture/capture.go

@@ -43,9 +43,21 @@ const capturedData key = "capturedData"
 // It satisfies the alice.Constructor type.
 func Wrap(next http.Handler) (http.Handler, error) {
 	return http.HandlerFunc(func(rw http.ResponseWriter, req *http.Request) {
-		c := &Capture{}
+		capt, err := FromContext(req.Context())
-		newRW, newReq := c.renew(rw, req)
+		if err != nil {
-		next.ServeHTTP(newRW, newReq)
+			c := &Capture{}
+			newRW, newReq := c.renew(rw, req)
+			next.ServeHTTP(newRW, newReq)
+			return
+		}
+
+		if capt.NeedsReset(rw) {
+			newRW, newReq := capt.renew(rw, req)
+			next.ServeHTTP(newRW, newReq)
+			return
+		}
+
+		next.ServeHTTP(rw, req)
 	}), nil
 }
 

pkg/server/service/service.go

@@ -21,6 +21,7 @@ import (
 	"github.com/traefik/traefik/v3/pkg/healthcheck"
 	"github.com/traefik/traefik/v3/pkg/logs"
 	"github.com/traefik/traefik/v3/pkg/middlewares/accesslog"
+	"github.com/traefik/traefik/v3/pkg/middlewares/capture"
 	metricsMiddle "github.com/traefik/traefik/v3/pkg/middlewares/metrics"
 	"github.com/traefik/traefik/v3/pkg/middlewares/observability"
 	"github.com/traefik/traefik/v3/pkg/safe"
@@ -342,6 +343,17 @@ func (m *Manager) getLoadBalancerServiceHandler(ctx context.Context, serviceName
 			proxy = observability.NewService(ctx, serviceName, proxy)
 		}
 
+		if m.observabilityMgr.ShouldAddAccessLogs(qualifiedSvcName) || m.observabilityMgr.ShouldAddMetrics(qualifiedSvcName) {
+			// Some piece of middleware, like the ErrorPage, are relying on this serviceBuilder to get the handler for a given service,
+			// to re-target the request to it.
+			// Those pieces of middleware can be configured on routes that expose a Traefik internal service.
+			// In such a case, observability for internals being optional, the capture probe could be absent from context (no wrap via the entrypoint).
+			// But if the service targeted by this piece of middleware is not an internal one,
+			// and requires observability, we still want the capture probe to be present in the request context.
+			// Makes sure a capture probe is in the request context.
+			proxy, _ = capture.Wrap(proxy)
+		}
+
 		lb.Add(proxyName, proxy, server.Weight)
 
 		// servers are considered UP by default.