🔥 feat(logger): Add predefined log formats

docs/middleware/logger.md

@@ -79,7 +79,7 @@ app.Use(logger.New(logger.Config{
     TimeZone:   "Asia/Shanghai",
     Done: func(c fiber.Ctx, logString []byte) {
         if c.Response().StatusCode() != fiber.StatusOK {
-            reporter.SendToSlack(logString) 
+            reporter.SendToSlack(logString)
         }
     },
 }))
@@ -88,6 +88,23 @@ app.Use(logger.New(logger.Config{
 app.Use(logger.New(logger.Config{
     DisableColors: true,
 }))
+
+// Use predefined formats 
+app.Use(logger.New(logger.Config{
+    Format: logger.FormatCommon,
+}))
+
+app.Use(logger.New(logger.Config{
+    Format: logger.FormatCombined,
+}))
+
+app.Use(logger.New(logger.Config{
+    Format: logger.FormatJSON, 
+}))
+
+app.Use(logger.New(logger.Config{
+    Format: logger.FormatECS, 
+}))
 ```
 
 ### Use Logger Middleware with Other Loggers
@@ -136,37 +153,50 @@ Writing to os.File is goroutine-safe, but if you are using a custom Stream that
 
 ### Config
 
-| Property         | Type                       | Description                                                                                                                      | Default                                                               |
-|:-----------------|:---------------------------|:---------------------------------------------------------------------------------------------------------------------------------|:----------------------------------------------------------------------|
-| Next             | `func(fiber.Ctx) bool`     | Next defines a function to skip this middleware when returned true.                                                               | `nil`                                                                 |
-| Skip             | `func(fiber.Ctx) bool`     | Skip is a function to determine if logging is skipped or written to Stream.                                                       | `nil`                                                                 |
-| Done             | `func(fiber.Ctx, []byte)`  | Done is a function that is called after the log string for a request is written to Stream, and pass the log string as parameter.  | `nil`                                                                 |
-| CustomTags       | `map[string]LogFunc`       | tagFunctions defines the custom tag action.                                                                                      | `map[string]LogFunc`                                                  |
-| Format           | `string`                   | Format defines the logging tags.                                                                                                 | `[${time}] ${ip} ${status} - ${latency} ${method} ${path} ${error}\n` |
-| TimeFormat       | `string`                   | TimeFormat defines the time format for log timestamps.                                                                           | `15:04:05`                                                            |
-| TimeZone         | `string`                   | TimeZone can be specified, such as "UTC" and "America/New_York" and "Asia/Chongqing", etc                                        | `"Local"`                                                             |
-| TimeInterval     | `time.Duration`            | TimeInterval is the delay before the timestamp is updated.                                                                       | `500 * time.Millisecond`                                              |
-| Stream           | `io.Writer`                | Stream is a writer where logs are written.                                                                                       | `os.Stdout`                                                           |
-| LoggerFunc | `func(c fiber.Ctx, data *Data, cfg Config) error` | Custom logger function for integration with logging libraries (Zerolog, Zap, Logrus, etc). Defaults to Fiber's default logger if not defined. | `see default_logger.go defaultLoggerInstance` |
-| DisableColors    | `bool`                     | DisableColors defines if the logs output should be colorized.                                                                    | `false`                                                               |
+| Property      | Type                                              | Description                                                                                                                                   | Default                                                               |
+| :------------ | :------------------------------------------------ | :-------------------------------------------------------------------------------------------------------------------------------------------- | :-------------------------------------------------------------------- |
+| Next          | `func(fiber.Ctx) bool`                            | Next defines a function to skip this middleware when returned true.                                                                           | `nil`                                                                 |
+| Skip          | `func(fiber.Ctx) bool`                            | Skip is a function to determine if logging is skipped or written to Stream.                                                                   | `nil`                                                                 |
+| Done          | `func(fiber.Ctx, []byte)`                         | Done is a function that is called after the log string for a request is written to Stream, and pass the log string as parameter.              | `nil`                                                                 |
+| CustomTags    | `map[string]LogFunc`                              | tagFunctions defines the custom tag action.                                                                                                   | `map[string]LogFunc`                                                  |
+| `Format`   | `string`  | Defines the logging tags. See more in [Predefined Formats](#predefined-formats), or create your own using [Tags](#constants). | `[${time}] ${ip} ${status} - ${latency} ${method} ${path} ${error}\n` (same as `DefaultFormat`) |
+| TimeFormat    | `string`                                          | TimeFormat defines the time format for log timestamps.                                                                                        | `15:04:05`                                                            |
+| TimeZone      | `string`                                          | TimeZone can be specified, such as "UTC" and "America/New_York" and "Asia/Chongqing", etc                                                     | `"Local"`                                                             |
+| TimeInterval  | `time.Duration`                                   | TimeInterval is the delay before the timestamp is updated.                                                                                    | `500 * time.Millisecond`                                              |
+| Stream        | `io.Writer`                                       | Stream is a writer where logs are written.                                                                                                    | `os.Stdout`                                                           |
+| LoggerFunc    | `func(c fiber.Ctx, data *Data, cfg Config) error` | Custom logger function for integration with logging libraries (Zerolog, Zap, Logrus, etc). Defaults to Fiber's default logger if not defined. | `see default_logger.go defaultLoggerInstance`                         |
+| DisableColors | `bool`                                            | DisableColors defines if the logs output should be colorized.                                                                                 | `false`                                                               |
 
 ## Default Config
 
 ```go
 var ConfigDefault = Config{
-    Next:          nil,
-    Skip           nil,
-    Done:          nil,
-    Format:        "[${time}] ${ip} ${status} - ${latency} ${method} ${path} ${error}\n",
-    TimeFormat:    "15:04:05",
-    TimeZone:      "Local",
-    TimeInterval:  500 * time.Millisecond,
-    Stream:        os.Stdout,
-    DisableColors: false,
-    LoggerFunc:    defaultLoggerInstance,
+    Next:              nil,
+    Skip:              nil,
+    Done:              nil,
+    Format:            DefaultFormat,
+    TimeFormat:        "15:04:05",
+    TimeZone:          "Local",
+    TimeInterval:      500 * time.Millisecond,
+    Stream:            os.Stdout,
+    BeforeHandlerFunc: beforeHandlerFunc,
+    LoggerFunc:        defaultLoggerInstance,
+    enableColors:      true,
 }
 ```
 
+## Predefined Formats
+
+Logger provides predefined formats that you can use by name or directly by specifying the format string.
+
+| **Format Constant** | **Format String** | **Description** |
+|---------------------|--------------------------------------------------------------------------------------------------------------------|-----------------------------------------------------------------------------------------------------|
+| `DefaultFormat` | `"[${time}] ${ip} ${status} - ${latency} ${method} ${path} ${error}\n"` | Fiber's default logger format. |
+| `CommonFormat` | `"${ip} - - [${time}] "${method} ${url} ${protocol}" ${status} ${bytesSent}\n"` | Common Log Format (CLF) used in web server logs. |
+| `CombinedFormat` | `"${ip} - - [${time}] "${method} ${url} ${protocol}" ${status} ${bytesSent} "${referer}" "${ua}"\n"` | CLF format plus the `referer` and `user agent` fields. |
+| `JSONFormat` | `"{time: ${time}, ip: ${ip}, method: ${method}, url: ${url}, status: ${status}, bytesSent: ${bytesSent}}\n"` | JSON format for structured logging. |
+| `ECSFormat` | `"{\"@timestamp\":\"${time}\",\"ecs\":{\"version\":\"1.6.0\"},\"client\":{\"ip\":\"${ip}\"},\"http\":{\"request\":{\"method\":\"${method}\",\"url\":\"${url}\",\"protocol\":\"${protocol}\"},\"response\":{\"status_code\":${status},\"body\":{\"bytes\":${bytesSent}}}},\"log\":{\"level\":\"INFO\",\"logger\":\"fiber\"},\"message\":\"${method} ${url} responded with ${status}\"}\n"` | Elastic Common Schema (ECS) format for structured logging. |
+
 ## Constants
 
 ```go

docs/whats_new.md

@@ -937,6 +937,22 @@ app.Use(logger.New(logger.Config{
 
 </details>
 
+#### Predefined Formats
+
+Logger provides predefined formats that you can use by name or directly by specifying the format string.
+<details>
+
+<summary>Example Usage</summary>
+
+```go
+app.Use(logger.New(logger.Config{
+    Format: logger.FormatCombined, 
+}))
+```
+
+See more in [Logger](./middleware/logger.md#predefined-formats)
+</details>
+
 ### Filesystem
 
 We've decided to remove filesystem middleware to clear up the confusion between static and filesystem middleware.

middleware/logger/config.go

@@ -50,9 +50,23 @@ type Config struct {
 
 	timeZoneLocation *time.Location
 
-	// Format defines the logging tags
+	// Format defines the logging format for the middleware.
 	//
-	// Optional. Default: [${time}] ${ip} ${status} - ${latency} ${method} ${path} ${error}
+	// You can customize the log output by defining a format string with placeholders
+	// such as: ${time}, ${ip}, ${status}, ${method}, ${path}, ${latency}, ${error}, etc.
+	// The full list of available placeholders can be found in 'tags.go' or at
+	// 'https://docs.gofiber.io/api/middleware/logger/#constants'.
+	//
+	// Fiber provides predefined logging formats that can be used directly:
+	//
+	//   - DefaultFormat    → Uses the default log format: "[${time}] ${ip} ${status} - ${latency} ${method} ${path} ${error}"
+	//   - CommonFormat     → Uses the Apache Common Log Format (CLF): "${ip} - - [${time}] \"${method} ${url} ${protocol}\" ${status} ${bytesSent}\n"
+	//   - CombinedFormat   → Uses the Apache Combined Log Format: "${ip} - - [${time}] \"${method} ${url} ${protocol}\" ${status} ${bytesSent} \"${referer}\" \"${ua}\"\n"
+	//   - JSONFormat      → Uses the JSON log format: "{\"time\":\"${time}\",\"ip\":\"${ip}\",\"method\":\"${method}\",\"url\":\"${url}\",\"status\":${status},\"bytesSent\":${bytesSent}}\n"
+	//   - ECSFormat        → Uses the Elastic Common Schema (ECS) log format: {\"@timestamp\":\"${time}\",\"ecs\":{\"version\":\"1.6.0\"},\"client\":{\"ip\":\"${ip}\"},\"http\":{\"request\":{\"method\":\"${method}\",\"url\":\"${url}\",\"protocol\":\"${protocol}\"},\"response\":{\"status_code\":${status},\"body\":{\"bytes\":${bytesSent}}}},\"log\":{\"level\":\"INFO\",\"logger\":\"fiber\"},\"message\":\"${method} ${url} responded with ${status}\"}"
+	// If both `Format` and `CustomFormat` are provided, the `CustomFormat` will be used, and the `Format` field will be ignored.
+	// If no format is specified, the default format is used:
+	// "[${time}] ${ip} ${status} - ${latency} ${method} ${path} ${error}"
 	Format string
 
 	// TimeFormat https://programming.guide/go/format-parse-string-time-date-example.html
@@ -105,7 +119,7 @@ var ConfigDefault = Config{
 	Next:              nil,
 	Skip:              nil,
 	Done:              nil,
-	Format:            defaultFormat,
+	Format:            DefaultFormat,
 	TimeFormat:        "15:04:05",
 	TimeZone:          "Local",
 	TimeInterval:      500 * time.Millisecond,
@@ -115,9 +129,6 @@ var ConfigDefault = Config{
 	enableColors:      true,
 }
 
-// default logging format for Fiber's default logger
-var defaultFormat = "[${time}] ${ip} ${status} - ${latency} ${method} ${path} ${error}\n"
-
 // Helper function to set default values
 func configDefault(config ...Config) Config {
 	// Return default config if nothing provided

middleware/logger/default_logger.go

@@ -28,7 +28,7 @@ func defaultLoggerInstance(c fiber.Ctx, data *Data, cfg Config) error {
 	buf := bytebufferpool.Get()
 
 	// Default output when no custom Format or io.Writer is given
-	if cfg.Format == defaultFormat {
+	if cfg.Format == DefaultFormat {
 		// Format error if exist
 		formatErr := ""
 		if cfg.enableColors {

middleware/logger/format.go

@@ -0,0 +1,14 @@
+package logger
+
+const (
+	// Fiber's default logger
+	DefaultFormat = "[${time}] ${ip} ${status} - ${latency} ${method} ${path} ${error}\n"
+	// Apache Common Log Format (CLF)
+	CommonFormat = "${ip} - - [${time}] \"${method} ${url} ${protocol}\" ${status} ${bytesSent}\n"
+	// Apache Combined Log Format
+	CombinedFormat = "${ip} - - [${time}] \"${method} ${url} ${protocol}\" ${status} ${bytesSent} \"${referer}\" \"${ua}\"\n"
+	// JSON log formats
+	JSONFormat = "{\"time\":\"${time}\",\"ip\":\"${ip}\",\"method\":\"${method}\",\"url\":\"${url}\",\"status\":${status},\"bytesSent\":${bytesSent}}\n"
+	// Elastic Common Schema (ECS) Log Format
+	ECSFormat = "{\"@timestamp\":\"${time}\",\"ecs\":{\"version\":\"1.6.0\"},\"client\":{\"ip\":\"${ip}\"},\"http\":{\"request\":{\"method\":\"${method}\",\"url\":\"${url}\",\"protocol\":\"${protocol}\"},\"response\":{\"status_code\":${status},\"body\":{\"bytes\":${bytesSent}}}},\"log\":{\"level\":\"INFO\",\"logger\":\"fiber\"},\"message\":\"${method} ${url} responded with ${status}\"}\n"
+)

middleware/logger/logger.go

@@ -40,7 +40,6 @@ func New(config ...Config) fiber.Handler {
 			}
 		}()
 	}
-
 	// Set PID once
 	pid := strconv.Itoa(os.Getpid())
 

middleware/logger/logger_test.go

@@ -467,6 +467,124 @@ func Test_Logger_All(t *testing.T) {
 	require.Equal(t, expected, buf.String())
 }
 
+func Test_Logger_CLF_Format(t *testing.T) {
+	t.Parallel()
+	buf := bytebufferpool.Get()
+	defer bytebufferpool.Put(buf)
+
+	app := fiber.New()
+
+	app.Use(New(Config{
+		Format: CommonFormat,
+		Stream: buf,
+	}))
+
+	resp, err := app.Test(httptest.NewRequest(fiber.MethodGet, "/?foo=bar", nil))
+	require.NoError(t, err)
+	require.Equal(t, fiber.StatusNotFound, resp.StatusCode)
+
+	expected := fmt.Sprintf("0.0.0.0 - - [%s] \"%s %s %s\" %d %d\n",
+		time.Now().Format("15:04:05"),
+		fiber.MethodGet, "/?foo=bar", "HTTP/1.1",
+		fiber.StatusNotFound,
+		0)
+	logResponse := buf.String()
+	require.Equal(t, expected, logResponse)
+}
+
+func Test_Logger_Combined_CLF_Format(t *testing.T) {
+	t.Parallel()
+	buf := bytebufferpool.Get()
+	defer bytebufferpool.Put(buf)
+
+	app := fiber.New()
+
+	app.Use(New(Config{
+		Format: CombinedFormat,
+		Stream: buf,
+	}))
+	const expectedUA = "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/74.0.3729.169 Safari/537.36"
+	const expectedReferer = "http://example.com"
+	req := httptest.NewRequest(fiber.MethodGet, "/?foo=bar", nil)
+	req.Header.Set("Referer", expectedReferer)
+	req.Header.Set("User-Agent", expectedUA)
+	resp, err := app.Test(req)
+	require.NoError(t, err)
+	require.Equal(t, fiber.StatusNotFound, resp.StatusCode)
+
+	expected := fmt.Sprintf("0.0.0.0 - - [%s] %q %d %d %q %q\n",
+		time.Now().Format("15:04:05"),
+		fmt.Sprintf("%s %s %s", fiber.MethodGet, "/?foo=bar", "HTTP/1.1"),
+		fiber.StatusNotFound,
+		0,
+		expectedReferer,
+		expectedUA)
+	logResponse := buf.String()
+	require.Equal(t, expected, logResponse)
+}
+
+func Test_Logger_Json_Format(t *testing.T) {
+	t.Parallel()
+	buf := bytebufferpool.Get()
+	defer bytebufferpool.Put(buf)
+
+	app := fiber.New()
+
+	app.Use(New(Config{
+		Format: JSONFormat,
+		Stream: buf,
+	}))
+
+	req := httptest.NewRequest(fiber.MethodGet, "/?foo=bar", nil)
+	resp, err := app.Test(req)
+	require.NoError(t, err)
+	require.Equal(t, fiber.StatusNotFound, resp.StatusCode)
+
+	expected := fmt.Sprintf(
+		"{\"time\":%q,\"ip\":%q,\"method\":%q,\"url\":%q,\"status\":%d,\"bytesSent\":%d}\n",
+		time.Now().Format("15:04:05"),
+		"0.0.0.0",
+		fiber.MethodGet,
+		"/?foo=bar",
+		fiber.StatusNotFound,
+		0,
+	)
+	logResponse := buf.String()
+	require.Equal(t, expected, logResponse)
+}
+
+func Test_Logger_ECS_Format(t *testing.T) {
+	t.Parallel()
+	buf := bytebufferpool.Get()
+	defer bytebufferpool.Put(buf)
+
+	app := fiber.New()
+
+	app.Use(New(Config{
+		Format: ECSFormat,
+		Stream: buf,
+	}))
+
+	req := httptest.NewRequest(fiber.MethodGet, "/?foo=bar", nil)
+	resp, err := app.Test(req)
+	require.NoError(t, err)
+	require.Equal(t, fiber.StatusNotFound, resp.StatusCode)
+
+	expected := fmt.Sprintf(
+		"{\"@timestamp\":%q,\"ecs\":{\"version\":\"1.6.0\"},\"client\":{\"ip\":%q},\"http\":{\"request\":{\"method\":%q,\"url\":%q,\"protocol\":%q},\"response\":{\"status_code\":%d,\"body\":{\"bytes\":%d}}},\"log\":{\"level\":\"INFO\",\"logger\":\"fiber\"},\"message\":%q}\n",
+		time.Now().Format("15:04:05"),
+		"0.0.0.0",
+		fiber.MethodGet,
+		"/?foo=bar",
+		"HTTP/1.1",
+		fiber.StatusNotFound,
+		0,
+		fmt.Sprintf("%s %s responded with %d", fiber.MethodGet, "/?foo=bar", fiber.StatusNotFound),
+	)
+	logResponse := buf.String()
+	require.Equal(t, expected, logResponse)
+}
+
 func getLatencyTimeUnits() []struct {
 	unit string
 	div  time.Duration