Add a new option to allow Stdio access logs alongsige OTLP logging

docs/content/reference/install-configuration/configuration-options.md

@@ -10,6 +10,7 @@ THIS FILE MUST NOT BE EDITED BY HAND
 | <a id="opt-accesslog" href="#opt-accesslog" title="#opt-accesslog">accesslog</a> | Access log settings. | false |
 | <a id="opt-accesslog-addinternals" href="#opt-accesslog-addinternals" title="#opt-accesslog-addinternals">accesslog.addinternals</a> | Enables access log for internal services (ping, dashboard, etc...). | false |
 | <a id="opt-accesslog-bufferingsize" href="#opt-accesslog-bufferingsize" title="#opt-accesslog-bufferingsize">accesslog.bufferingsize</a> | Number of access log lines to process in a buffered way. | 0 |
+| <a id="opt-accesslog-dualoutput" href="#opt-accesslog-dualoutput" title="#opt-accesslog-dualoutput">accesslog.dualoutput</a> | Enables access log output alongside OTLP. By default, this output is disabled when OTLP is configured. | false |
 | <a id="opt-accesslog-fields-defaultmode" href="#opt-accesslog-fields-defaultmode" title="#opt-accesslog-fields-defaultmode">accesslog.fields.defaultmode</a> | Default mode for fields: keep | drop | keep |
 | <a id="opt-accesslog-fields-headers-defaultmode" href="#opt-accesslog-fields-headers-defaultmode" title="#opt-accesslog-fields-headers-defaultmode">accesslog.fields.headers.defaultmode</a> | Default mode for fields: keep | drop | redact | drop |
 | <a id="opt-accesslog-fields-headers-names-name" href="#opt-accesslog-fields-headers-names-name" title="#opt-accesslog-fields-headers-names-name">accesslog.fields.headers.names._name_</a> | Override mode for headers | |

docs/content/reference/install-configuration/observability/logs-and-accesslogs.md

@@ -141,6 +141,9 @@ Traefik also supports the `OTEL_RESOURCE_ATTRIBUTES` env variable to set up the
 
 Access logs concern everything that happens to the requests handled by Traefik.
 
+!!! note "Stdio logs are not enabled by default alongside OTLP exports"
+    If you would like Stdio access logs to be available, use [accessLog.dualOutput](#opt-accesslog-dualOutput) option.
+
 ### Configuration Example
 
 ```yaml tab="File (YAML)"
@@ -195,6 +198,7 @@ accessLog:
 
 ```sh tab="CLI"
 --accesslog=true
+--accesslog.dualoutput=true
 --accesslog.format=json
 --accesslog.filters.statuscodes=200,300-302
 --accesslog.filters.retryattempts
@@ -213,6 +217,7 @@ The section below describes how to configure Traefik access logs using the stati
 | Field      | Description    | Default | Required |
 |:-----------|:--------------------------|:--------|:---------|
 | <a id="opt-accesslog-filePath" href="#opt-accesslog-filePath" title="#opt-accesslog-filePath">`accesslog.filePath`</a> | By default, the access logs are written to the standard output.<br />You can configure a file path instead using the `filePath` option.|  | No      |
+| <a id="opt-accesslog-dualOutput" href="#opt-accesslog-dualOutput" title="#opt-accesslog-dualOutput">`accesslog.dualOutput`</a> | Force Stdio logging, even if OTLP is configured. By default, Stdio logging is disabled when OTLP is enabled for performance reasons. | false      | No      |
 | <a id="opt-accesslog-format" href="#opt-accesslog-format" title="#opt-accesslog-format">`accesslog.format`</a> | By default, logs are written using the Traefik Common Log Format (CLF).<br />Available formats: [`common`](#traefik-clf-format-fields) (Traefik extended CLF), [`genericCLF`](#generic-clf-format-fields) (standard CLF compatible with analyzers), or [`json`](#json-format-fields).<br />If the given format is unsupported, the default (`common`) is used instead. | "common" | No      |
 | <a id="opt-accesslog-bufferingSize" href="#opt-accesslog-bufferingSize" title="#opt-accesslog-bufferingSize">`accesslog.bufferingSize`</a> | To write the logs in an asynchronous fashion, specify a  `bufferingSize` option.<br />This option represents the number of log lines Traefik will keep in memory before writing them to the selected output.<br />In some cases, this option can greatly help performances.| 0 | No      |
 | <a id="opt-accesslog-addInternals" href="#opt-accesslog-addInternals" title="#opt-accesslog-addInternals">`accesslog.addInternals`</a> | Enables access logs for internal resources (e.g.: `ping@internal`). | false  | No      |
@@ -252,6 +257,8 @@ experimental:
   otlpLogs: true
 
 accesslog:
+  # Keep Stdio logs alongside OTEL logging
+  dualOutput: true
   otlp:
     http:
       endpoint: https://collector:4318/v1/logs
@@ -263,6 +270,9 @@ accesslog:
 [experimental]
   otlpLogs = true
 
+[accessLog]
+  dualOutput = true
+
 [accesslog.otlp]
   http.endpoint = "https://collector:4318/v1/logs"
   http.headers.Authorization = "Bearer auth_asKXRhIMplM7El1JENjrotGouS1LYRdL"

pkg/middlewares/accesslog/logger.go

@@ -128,8 +128,10 @@ func NewHandler(ctx context.Context, config *otypes.AccessLog) (*Handler, error)
 		}
 
 		logger.Hooks.Add(otellogrus.NewHook("traefik", otellogrus.WithLoggerProvider(otelLoggerProvider)))
+		if !config.DualOutput {
 			logger.Out = io.Discard
 		}
+	}
 
 	// Transform header names to a canonical form, to be used as is without further transformations,
 	// and transform field names to lower case, to enable case-insensitive lookup.

pkg/middlewares/accesslog/logger_test.go

@@ -21,6 +21,7 @@ import (
 	"time"
 
 	"github.com/containous/alice"
+	"github.com/sirupsen/logrus"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 	ptypes "github.com/traefik/paerser/types"
@@ -56,41 +57,99 @@ var (
 	testStart               = time.Now()
 )
 
-func TestOTelAccessLogWithBody(t *testing.T) {
+func TestOTelAccessLogWithBodyAndDualOutput(t *testing.T) {
 	testCases := []struct {
 		desc             string
 		format           string
+		filePath         string
+		dualOutput       bool
 		bodyCheckFn      func(*testing.T, string)
+		outLoggerCheckFn func(*testing.T, *logrus.Logger)
 	}{
 		{
 			desc:       "Common format with log body",
 			format:     CommonFormat,
+			filePath:   "",
+			dualOutput: false,
 			bodyCheckFn: func(t *testing.T, log string) {
 				t.Helper()
 
 				// For common format, verify the body contains the Traefik common log formatted string
 				assert.Regexp(t, `"body":{"stringValue":".*- /health -.*200.*[0-9]+ms.*"}`, log)
 			},
+			outLoggerCheckFn: func(t *testing.T, l *logrus.Logger) {
+				t.Helper()
+
+				assert.Equal(t, l.Out, io.Discard)
+			},
 		},
 		{
 			desc:       "Generic CLF format with log body",
 			format:     GenericCLFFormat,
+			filePath:   "",
+			dualOutput: false,
 			bodyCheckFn: func(t *testing.T, log string) {
 				t.Helper()
 
 				// For generic CLF format, verify the body contains the CLF formatted string
 				assert.Regexp(t, `"body":{"stringValue":".*- /health -.*200.*"}`, log)
 			},
+			outLoggerCheckFn: func(t *testing.T, l *logrus.Logger) {
+				t.Helper()
+
+				assert.Equal(t, l.Out, io.Discard)
+			},
 		},
 		{
 			desc:       "JSON format with log body",
 			format:     JSONFormat,
+			filePath:   "",
+			dualOutput: false,
 			bodyCheckFn: func(t *testing.T, log string) {
 				t.Helper()
 
 				// For JSON format, verify the body contains the JSON formatted string
 				assert.Regexp(t, `"body":{"stringValue":".*DownstreamStatus.*:200.*"}`, log)
 			},
+			outLoggerCheckFn: func(t *testing.T, l *logrus.Logger) {
+				t.Helper()
+
+				assert.Equal(t, l.Out, io.Discard)
+			},
+		},
+		{
+			desc:       "Common format with log body and Dual Output (STDOUT + OTEL)",
+			format:     CommonFormat,
+			filePath:   "",
+			dualOutput: true,
+			bodyCheckFn: func(t *testing.T, log string) {
+				t.Helper()
+
+				// For common format, verify the body contains the Traefik common log formatted string
+				assert.Regexp(t, `"body":{"stringValue":".*- /health -.*200.*[0-9]+ms.*"}`, log)
+			},
+			outLoggerCheckFn: func(t *testing.T, l *logrus.Logger) {
+				t.Helper()
+
+				assert.NotEqual(t, l.Out, io.Discard)
+			},
+		},
+		{
+			desc:       "Common format with log body and Dual Output (File logging + OTEL)",
+			format:     CommonFormat,
+			filePath:   filepath.Join(t.TempDir(), "traefik.log"),
+			dualOutput: true,
+			bodyCheckFn: func(t *testing.T, log string) {
+				t.Helper()
+
+				// For common format, verify the body contains the Traefik common log formatted string
+				assert.Regexp(t, `"body":{"stringValue":".*- /health -.*200.*[0-9]+ms.*"}`, log)
+			},
+			outLoggerCheckFn: func(t *testing.T, l *logrus.Logger) {
+				t.Helper()
+
+				assert.NotEqual(t, l.Out, io.Discard)
+			},
 		},
 	}
 
@@ -119,6 +178,8 @@ func TestOTelAccessLogWithBody(t *testing.T) {
 
 			config := &otypes.AccessLog{
 				Format:     test.format,
+				DualOutput: test.dualOutput,
+				FilePath:   test.filePath,
 				OTLP: &otypes.OTelLog{
 					ServiceName:        "test",
 					ResourceAttributes: map[string]string{"resource": "attribute"},
@@ -179,6 +240,9 @@ func TestOTelAccessLogWithBody(t *testing.T) {
 
 				// Run format-specific body checks
 				test.bodyCheckFn(t, log)
+
+				// Run OUT logger checks
+				test.outLoggerCheckFn(t, logHandler.logger)
 			}
 		})
 	}

pkg/observability/types/logs.go

@@ -64,6 +64,7 @@ type AccessLog struct {
 	Fields        *AccessLogFields  `description:"AccessLogFields." json:"fields,omitempty" toml:"fields,omitempty" yaml:"fields,omitempty" export:"true"`
 	BufferingSize int64             `description:"Number of access log lines to process in a buffered way." json:"bufferingSize,omitempty" toml:"bufferingSize,omitempty" yaml:"bufferingSize,omitempty" export:"true"`
 	AddInternals  bool              `description:"Enables access log for internal services (ping, dashboard, etc...)." json:"addInternals,omitempty" toml:"addInternals,omitempty" yaml:"addInternals,omitempty" export:"true"`
+	DualOutput    bool              `description:"Enables access log output alongside OTLP. By default, this output is disabled when OTLP is configured." json:"dualOutput,omitempty" toml:"dualOutput,omitempty" yaml:"dualOutput,omitempty" export:"true"`
 
 	OTLP *OTelLog `description:"Settings for OpenTelemetry." json:"otlp,omitempty" toml:"otlp,omitempty" yaml:"otlp,omitempty" label:"allowEmpty" file:"allowEmpty" export:"true"`
 }