Add GenericCLF log format for access logs

docs/content/observability/access-logs.md

@@ -69,27 +69,43 @@ accessLog:
 
 _Optional, Default="common"_
 
-By default, logs are written using the Common Log Format (CLF).
-To write logs in JSON, use `json` in the `format` option.
-If the given format is unsupported, the default (CLF) is used instead.
+By default, logs are written using the Traefik Common Log Format (CLF).
+The available log formats are:
 
-!!! info "Common Log Format"
+- `common` - Traefik's extended CLF format (default)
+- `genericCLF` - Generic CLF format compatible with standard log analyzers
+- `json` - JSON format for structured logging
 
+If the given format is unsupported, the default (`common`) is used instead.
+
+!!! info "Traefik Common Log Format vs Generic CLF"
+
+    **Traefik Common Log Format (`common`):**
     ```html
     <remote_IP_address> - <client_user_name_if_available> [<timestamp>] "<request_method> <request_path> <request_protocol>" <HTTP_status> <content-length> "<request_referrer>" "<request_user_agent>" <number_of_requests_received_since_Traefik_started> "<Traefik_router_name>" "<Traefik_server_URL>" <request_duration_in_ms>ms
     ```
     
+    **Generic CLF Format (`genericCLF`):**
+    ```html
+    <remote_IP_address> - <client_user_name_if_available> [<timestamp>] "<request_method> <request_path> <request_protocol>" <HTTP_status> <content-length> "<request_referrer>" "<request_user_agent>"
+    ```
+    
+    The `genericCLF` format omits Traefik-specific fields (request count, router name, service URL, and duration) for better compatibility with standard CLF parsers.
+
 ```yaml tab="File (YAML)"
+# JSON format
 accessLog:
   format: "json"
 ```
 
 ```toml tab="File (TOML)"
+# JSON format
 [accessLog]
   format = "json"
 ```
 
 ```bash tab="CLI"
+# JSON format
 --accesslog.format=json
 ```
 

docs/content/observe/logs-and-access-logs.md

@@ -155,8 +155,9 @@ When the `observability` options are not defined on a router, it inherits the be
 
 Traefik Proxy supports the following log formats:
 
-- Common Log Format (CLF)
-- JSON
+- `common` - Traefik's extended CLF format (default)
+- `genericCLF` - Generic CLF format compatible with standard log analyzers
+- `json` - JSON format for structured logging
 
 ## Access Log Filters
 

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

@@ -18,7 +18,7 @@ THIS FILE MUST NOT BE EDITED BY HAND
 | accesslog.filters.minduration | Keep access logs when request took longer than the specified duration. | 0 |
 | accesslog.filters.retryattempts | Keep access logs when at least one retry happened. | false |
 | accesslog.filters.statuscodes | Keep access logs with status codes in the specified range. | |
-| accesslog.format | Access log format: json | common | common |
+| accesslog.format | Access log format: json, common, or genericCLF | common |
 | accesslog.otlp | Settings for OpenTelemetry. | false |
 | accesslog.otlp.grpc | gRPC configuration for the OpenTelemetry collector. | false |
 | accesslog.otlp.grpc.endpoint | Sets the gRPC endpoint (host:port) of the collector. | localhost:4317 |

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

@@ -195,7 +195,7 @@ The section below describes how to configure Traefik access logs using the stati
 | Field      | Description    | Default | Required |
 |:-----------|:--------------------------|:--------|:---------|
 | `accesslog.filePath` | By default, the access logs are written to the standard output.<br />You can configure a file path instead using the `filePath` option.|  | No      |
-| `accesslog.format` | By default, logs are written using the Common Log Format (CLF).<br />To write logs in JSON, use `json` in the `format` option.<br />If the given format is unsupported, the default (CLF) is used instead.<br />More information about CLF fields [here](#clf-format-fields). | "common" | No      |
+| `accesslog.format` | By default, logs are written using the Traefik Common Log Format (CLF).<br />Available formats: `common` (Traefik's extended CLF), `genericCLF` (standard CLF compatible with analyzers), or `json`.<br />If the given format is unsupported, the default (`common`) is used instead.<br />More information about CLF fields [here](#clf-format-fields). | "common" | No      |
 | `accesslog.bufferingSize` | 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      |
 | `accesslog.addInternals` | Enables access logs for internal resources (e.g.: `ping@internal`). | false  | No      |
 | `accesslog.filters.statusCodes` | Limit the access logs to requests with a status codes in the specified range. | [ ]      | No      |

pkg/middlewares/accesslog/logger.go

@@ -37,6 +37,9 @@ const (
 	// CommonFormat is the common logging format (CLF).
 	CommonFormat string = "common"
 
+	// GenericCLFFormat is the generic CLF format.
+	GenericCLFFormat string = "genericCLF"
+
 	// JSONFormat is the JSON logging format.
 	JSONFormat string = "json"
 )
@@ -101,6 +104,8 @@ func NewHandler(ctx context.Context, config *types.AccessLog) (*Handler, error)
 	switch config.Format {
 	case CommonFormat:
 		formatter = new(CommonLogFormatter)
+	case GenericCLFFormat:
+		formatter = new(GenericCLFLogFormatter)
 	case JSONFormat:
 		formatter = new(logrus.JSONFormatter)
 	default:

pkg/middlewares/accesslog/logger_formatters.go

@@ -52,6 +52,35 @@ func (f *CommonLogFormatter) Format(entry *logrus.Entry) ([]byte, error) {
 	return b.Bytes(), err
 }
 
+// GenericCLFLogFormatter provides formatting in the generic CLF log format.
+type GenericCLFLogFormatter struct{}
+
+// Format formats the log entry in the generic CLF log format.
+func (f *GenericCLFLogFormatter) Format(entry *logrus.Entry) ([]byte, error) {
+	b := &bytes.Buffer{}
+
+	timestamp := defaultValue
+	if v, ok := entry.Data[StartUTC]; ok {
+		timestamp = v.(time.Time).Format(commonLogTimeFormat)
+	} else if v, ok := entry.Data[StartLocal]; ok {
+		timestamp = v.(time.Time).Local().Format(commonLogTimeFormat)
+	}
+
+	_, err := fmt.Fprintf(b, "%s - %s [%s] \"%s %s %s\" %v %v %s %s\n",
+		toLog(entry.Data, ClientHost, defaultValue, false),
+		toLog(entry.Data, ClientUsername, defaultValue, false),
+		timestamp,
+		toLog(entry.Data, RequestMethod, defaultValue, false),
+		toLog(entry.Data, RequestPath, defaultValue, false),
+		toLog(entry.Data, RequestProtocol, defaultValue, false),
+		toLog(entry.Data, DownstreamStatus, defaultValue, true),
+		toLog(entry.Data, DownstreamContentSize, defaultValue, true),
+		toLog(entry.Data, "request_Referer", `"-"`, true),
+		toLog(entry.Data, "request_User-Agent", `"-"`, true))
+
+	return b.Bytes(), err
+}
+
 func toLog(fields logrus.Fields, key, defaultValue string, quoted bool) interface{} {
 	if v, ok := fields[key]; ok {
 		if v == nil {

pkg/middlewares/accesslog/logger_formatters_test.go

@@ -101,6 +101,97 @@ func TestCommonLogFormatter_Format(t *testing.T) {
 	}
 }
 
+func TestGenericCLFLogFormatter_Format(t *testing.T) {
+	clf := GenericCLFLogFormatter{}
+
+	testCases := []struct {
+		name        string
+		data        map[string]interface{}
+		expectedLog string
+	}{
+		{
+			name: "DownstreamStatus & DownstreamContentSize are nil",
+			data: map[string]interface{}{
+				StartUTC:               time.Date(2009, time.November, 10, 23, 0, 0, 0, time.UTC),
+				Duration:               123 * time.Second,
+				ClientHost:             "10.0.0.1",
+				ClientUsername:         "Client",
+				RequestMethod:          http.MethodGet,
+				RequestPath:            "/foo",
+				RequestProtocol:        "http",
+				DownstreamStatus:       nil,
+				DownstreamContentSize:  nil,
+				RequestRefererHeader:   "",
+				RequestUserAgentHeader: "",
+				RequestCount:           0,
+				RouterName:             "",
+				ServiceURL:             "",
+			},
+			expectedLog: `10.0.0.1 - Client [10/Nov/2009:23:00:00 +0000] "GET /foo http" - - "-" "-"
+`,
+		},
+		{
+			name: "all data",
+			data: map[string]interface{}{
+				StartUTC:               time.Date(2009, time.November, 10, 23, 0, 0, 0, time.UTC),
+				Duration:               123 * time.Second,
+				ClientHost:             "10.0.0.1",
+				ClientUsername:         "Client",
+				RequestMethod:          http.MethodGet,
+				RequestPath:            "/foo",
+				RequestProtocol:        "http",
+				DownstreamStatus:       123,
+				DownstreamContentSize:  132,
+				RequestRefererHeader:   "referer",
+				RequestUserAgentHeader: "agent",
+				RequestCount:           nil,
+				RouterName:             "foo",
+				ServiceURL:             "http://10.0.0.2/toto",
+			},
+			expectedLog: `10.0.0.1 - Client [10/Nov/2009:23:00:00 +0000] "GET /foo http" 123 132 "referer" "agent"
+`,
+		},
+		{
+			name: "all data with local time",
+			data: map[string]interface{}{
+				StartLocal:             time.Date(2009, time.November, 10, 23, 0, 0, 0, time.UTC),
+				Duration:               123 * time.Second,
+				ClientHost:             "10.0.0.1",
+				ClientUsername:         "Client",
+				RequestMethod:          http.MethodGet,
+				RequestPath:            "/foo",
+				RequestProtocol:        "http",
+				DownstreamStatus:       123,
+				DownstreamContentSize:  132,
+				RequestRefererHeader:   "referer",
+				RequestUserAgentHeader: "agent",
+				RequestCount:           nil,
+				RouterName:             "foo",
+				ServiceURL:             "http://10.0.0.2/toto",
+			},
+			expectedLog: `10.0.0.1 - Client [10/Nov/2009:14:00:00 -0900] "GET /foo http" 123 132 "referer" "agent"
+`,
+		},
+	}
+
+	var err error
+	time.Local, err = time.LoadLocation("Etc/GMT+9")
+	require.NoError(t, err)
+
+	for _, test := range testCases {
+		t.Run(test.name, func(t *testing.T) {
+			t.Parallel()
+
+			entry := &logrus.Entry{Data: test.data}
+
+			raw, err := clf.Format(entry)
+			assert.NoError(t, err)
+
+			assert.Equal(t, test.expectedLog, string(raw))
+		})
+	}
+}
+
 func Test_toLog(t *testing.T) {
 	testCases := []struct {
 		desc         string

pkg/middlewares/accesslog/logger_test.go

@@ -68,7 +68,17 @@ func TestOTelAccessLogWithBody(t *testing.T) {
 			bodyCheckFn: func(t *testing.T, log string) {
 				t.Helper()
 
-				// For common format, verify the body contains the CLF formatted string
+				// For common format, verify the body contains the Traefik common log formatted string
+				assert.Regexp(t, `"body":{"stringValue":".*- /health -.*200.*[0-9]+ms.*"}`, log)
+			},
+		},
+		{
+			desc:   "Generic CLF format with log body",
+			format: GenericCLFFormat,
+			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)
 			},
 		},
@@ -375,7 +385,7 @@ func TestLoggerHeaderFields(t *testing.T) {
 	}
 }
 
-func TestLoggerCLF(t *testing.T) {
+func TestCommonLogger(t *testing.T) {
 	logFilePath := filepath.Join(t.TempDir(), logFileNameSuffix)
 	config := &types.AccessLog{FilePath: logFilePath, Format: CommonFormat}
 	doLogging(t, config, false)
@@ -384,10 +394,10 @@ func TestLoggerCLF(t *testing.T) {
 	require.NoError(t, err)
 
 	expectedLog := ` TestHost - TestUser [13/Apr/2016:07:14:19 -0700] "POST testpath HTTP/0.0" 123 12 "testReferer" "testUserAgent" 1 "testRouter" "http://127.0.0.1/testService" 1ms`
-	assertValidLogData(t, expectedLog, logData)
+	assertValidCommonLogData(t, expectedLog, logData)
 }
 
-func TestLoggerCLFWithBufferingSize(t *testing.T) {
+func TestCommonLoggerWithBufferingSize(t *testing.T) {
 	logFilePath := filepath.Join(t.TempDir(), logFileNameSuffix)
 	config := &types.AccessLog{FilePath: logFilePath, Format: CommonFormat, BufferingSize: 1024}
 	doLogging(t, config, false)
@@ -399,7 +409,34 @@ func TestLoggerCLFWithBufferingSize(t *testing.T) {
 	require.NoError(t, err)
 
 	expectedLog := ` TestHost - TestUser [13/Apr/2016:07:14:19 -0700] "POST testpath HTTP/0.0" 123 12 "testReferer" "testUserAgent" 1 "testRouter" "http://127.0.0.1/testService" 1ms`
-	assertValidLogData(t, expectedLog, logData)
+	assertValidCommonLogData(t, expectedLog, logData)
+}
+
+func TestLoggerGenericCLF(t *testing.T) {
+	logFilePath := filepath.Join(t.TempDir(), logFileNameSuffix)
+	config := &types.AccessLog{FilePath: logFilePath, Format: GenericCLFFormat}
+	doLogging(t, config, false)
+
+	logData, err := os.ReadFile(logFilePath)
+	require.NoError(t, err)
+
+	expectedLog := ` TestHost - TestUser [13/Apr/2016:07:14:19 -0700] "POST testpath HTTP/0.0" 123 12 "testReferer" "testUserAgent"`
+	assertValidGenericCLFLogData(t, expectedLog, logData)
+}
+
+func TestLoggerGenericCLFWithBufferingSize(t *testing.T) {
+	logFilePath := filepath.Join(t.TempDir(), logFileNameSuffix)
+	config := &types.AccessLog{FilePath: logFilePath, Format: GenericCLFFormat, BufferingSize: 1024}
+	doLogging(t, config, false)
+
+	// wait a bit for the buffer to be written in the file.
+	time.Sleep(50 * time.Millisecond)
+
+	logData, err := os.ReadFile(logFilePath)
+	require.NoError(t, err)
+
+	expectedLog := ` TestHost - TestUser [13/Apr/2016:07:14:19 -0700] "POST testpath HTTP/0.0" 123 12 "testReferer" "testUserAgent"`
+	assertValidGenericCLFLogData(t, expectedLog, logData)
 }
 
 func assertString(exp string) func(t *testing.T, actual interface{}) {
@@ -963,12 +1000,12 @@ func TestNewLogHandlerOutputStdout(t *testing.T) {
 
 			written, err := os.ReadFile(file.Name())
 			require.NoError(t, err, "unable to read captured stdout from file")
-			assertValidLogData(t, test.expectedLog, written)
+			assertValidCommonLogData(t, test.expectedLog, written)
 		})
 	}
 }
 
-func assertValidLogData(t *testing.T, expected string, logData []byte) {
+func assertValidCommonLogData(t *testing.T, expected string, logData []byte) {
 	t.Helper()
 
 	if len(expected) == 0 {
@@ -1001,6 +1038,35 @@ func assertValidLogData(t *testing.T, expected string, logData []byte) {
 	assert.Regexp(t, `\d*ms`, result[Duration], formatErrMessage)
 }
 
+func assertValidGenericCLFLogData(t *testing.T, expected string, logData []byte) {
+	t.Helper()
+
+	if len(expected) == 0 {
+		assert.Empty(t, logData)
+		t.Log(string(logData))
+		return
+	}
+
+	result, err := ParseAccessLog(string(logData))
+	require.NoError(t, err)
+
+	resultExpected, err := ParseAccessLog(expected)
+	require.NoError(t, err)
+
+	formatErrMessage := fmt.Sprintf("Expected:\t%q\nActual:\t%q", expected, string(logData))
+
+	require.Len(t, result, len(resultExpected), formatErrMessage)
+	assert.Equal(t, resultExpected[ClientHost], result[ClientHost], formatErrMessage)
+	assert.Equal(t, resultExpected[ClientUsername], result[ClientUsername], formatErrMessage)
+	assert.Equal(t, resultExpected[RequestMethod], result[RequestMethod], formatErrMessage)
+	assert.Equal(t, resultExpected[RequestPath], result[RequestPath], formatErrMessage)
+	assert.Equal(t, resultExpected[RequestProtocol], result[RequestProtocol], formatErrMessage)
+	assert.Equal(t, resultExpected[OriginStatus], result[OriginStatus], formatErrMessage)
+	assert.Equal(t, resultExpected[OriginContentSize], result[OriginContentSize], formatErrMessage)
+	assert.Equal(t, resultExpected[RequestRefererHeader], result[RequestRefererHeader], formatErrMessage)
+	assert.Equal(t, resultExpected[RequestUserAgentHeader], result[RequestUserAgentHeader], formatErrMessage)
+}
+
 func captureStdout(t *testing.T) (out *os.File, restoreStdout func()) {
 	t.Helper()
 

pkg/types/logs.go

@@ -58,7 +58,7 @@ func (l *TraefikLog) SetDefaults() {
 // AccessLog holds the configuration settings for the access logger (middlewares/accesslog).
 type AccessLog struct {
 	FilePath      string            `description:"Access log file path. Stdout is used when omitted or empty." json:"filePath,omitempty" toml:"filePath,omitempty" yaml:"filePath,omitempty"`
-	Format        string            `description:"Access log format: json | common" json:"format,omitempty" toml:"format,omitempty" yaml:"format,omitempty" export:"true"`
+	Format        string            `description:"Access log format: json, common, or genericCLF" json:"format,omitempty" toml:"format,omitempty" yaml:"format,omitempty" export:"true"`
 	Filters       *AccessLogFilters `description:"Access log filters, used to keep only specific access logs." json:"filters,omitempty" toml:"filters,omitempty" yaml:"filters,omitempty" export:"true"`
 	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"`

traefik.sample.toml

@@ -81,12 +81,16 @@
   #
   # filePath = "/path/to/log/log.txt"
 
-  # Format is either "json" or "common".
+  # Format is either "json", "common", or "genericCLF".
+  # - "common": Traefik's extended CLF format (default)
+  # - "genericCLF": Standard CLF format compatible with standard log analyzers
+  # - "json": JSON format for structured logging
   #
   # Optional
   # Default: "common"
   #
   # format = "json"
+  # format = "genericCLF"
 
 ################################################################
 # API and dashboard configuration

traefik.sample.yml

@@ -79,12 +79,16 @@ entryPoints:
   #
 #  filePath: /path/to/log/log.txt
 
-  # Format is either "json" or "common".
+  # Format is either "json", "common", or "genericCLF".
+  # - "common": Traefik's extended CLF format (default)
+  # - "genericCLF": Standard CLF format compatible with standard log analyzers
+  # - "json": JSON format for structured logging
   #
   # Optional
   # Default: "common"
   #
 #  format: json
+#  format: genericCLF
 
 ################################################################
 # API and dashboard configuration