🔥 Feature: Add AllLogger to Config (#3153)

* 🔥 Feature: Add SetFlags to Logger Interface

🔥 Feature: Add fiberlog Logger field to config

* 🚨 Test: custom-defined Logger and LoggerFunc

* 📚 Doc: add LoggerFunc and Logger to middleware logger

* 🚨 Test: fine-tune custom Logger and LoggerFunc

* 📚 Doc: add Logger documentation

📚 Doc: add custom Logger example

* 🩹 fix: add default Logger field to default config

* 📚 Doc: remove Logger field in middleware logger

📚 Doc: add example of using fiber logger interface

* 🚨 Test: add tests for using fiber logger interface wrapper

* 📚 Doc: update custom logger example

* Update docs/middleware/logger.md

Co-authored-by: coderabbitai[bot] <136622811+coderabbitai[bot]@users.noreply.github.com>

* update

* update logger docs

* update what's new

* replace setflags with getloggerinstance

* fix linter

* update

* Fix markdownlint issues

* apply reviews & improve coverage

* fix linter

* rename controllogger

* Update whats_new.md

expandable example

---------

Co-authored-by: RW <rene@gofiber.io>
Co-authored-by: coderabbitai[bot] <136622811+coderabbitai[bot]@users.noreply.github.com>
Co-authored-by: Muhammed Efe Cetin <efectn@protonmail.com>
Co-authored-by: Juan Calderon-Perez <835733+gaby@users.noreply.github.com>

docs/api/log.md

@@ -36,7 +36,7 @@ type CommonLogger interface {
 
 type AllLogger interface {
     CommonLogger
-    ControlLogger
+    ConfigurableLogger
     WithLogger
 }
 ```
@@ -186,3 +186,19 @@ commonLogger.Info("info")
 ```
 
 Binding the logger to a context allows you to include context-specific information in your logs, improving traceability and debugging.
+
+## Logger
+
+You can use Logger to retrieve the logger instance. It is useful when you need to access underlying methods of the logger.
+To retrieve the Logger instance, use the following method:
+
+```go
+logger := fiberlog.DefaultLogger() // Call DefaultLogger to get the default logger instance
+
+stdlogger, ok := logger.Logger().(*log.Logger) // Get the logger instance and assert it to *log.Logger
+if !ok {
+    panic("logger is not *log.Logger")
+}
+
+stdlogger.SetFlags(0) // Hide timestamp by setting flags to 0
+```

docs/middleware/logger.md

@@ -90,6 +90,44 @@ app.Use(logger.New(logger.Config{
 }))
 ```
 
+### Use Logger Middleware with Other Loggers
+
+In order to use Fiber logger middleware with other loggers such as zerolog, zap, logrus; you can use `LoggerToWriter` helper which converts Fiber logger to a writer, which is compatible with the middleware.
+
+```go
+package main
+
+import (
+    "github.com/gofiber/contrib/fiberzap/v2"
+    "github.com/gofiber/fiber/v3"
+    "github.com/gofiber/fiber/v3/log"
+    "github.com/gofiber/fiber/v3/middleware/logger"
+)
+
+func main() {
+    // Create a new Fiber instance
+    app := fiber.New()
+
+    // Create a new zap logger which is compatible with Fiber AllLogger interface
+    zap := fiberzap.NewLogger(fiberzap.LoggerConfig{
+        ExtraKeys: []string{"request_id"},
+    })
+
+    // Use the logger middleware with zerolog logger
+    app.Use(logger.New(logger.Config{
+        Output: logger.LoggerToWriter(zap, log.LevelDebug),
+    }))
+
+    // Define a route
+    app.Get("/", func(c fiber.Ctx) error {
+        return c.SendString("Hello, World!")
+    })
+
+    // Start server on http://localhost:3000
+    app.Listen(":3000")
+}
+```
+
 :::tip
 Writing to os.File is goroutine-safe, but if you are using a custom Output that is not goroutine-safe, make sure to implement locking to properly serialize writes.
 :::
@@ -108,6 +146,7 @@ Writing to os.File is goroutine-safe, but if you are using a custom Output that
 | 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`                                              |
 | Output           | `io.Writer`                | Output 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`                                                               |
 | enableColors     | `bool`                     | Internal field for enabling colors in the log output. (This is not a user-configurable field)                                    | -                                                                     |
 | enableLatency    | `bool`                     | Internal field for enabling latency measurement in logs. (This is not a user-configurable field)                                 | -                                                                     |
@@ -125,6 +164,7 @@ var ConfigDefault = Config{
     TimeInterval:  500 * time.Millisecond,
     Output:        os.Stdout,
     DisableColors: false,
+    LoggerFunc:    defaultLoggerInstance,
 }
 ```
 

docs/whats_new.md

@@ -22,10 +22,12 @@ Here's a quick overview of the changes in Fiber `v3`:
 - [🔄️ Redirect](#-redirect)
 - [🌎 Client package](#-client-package)
 - [🧰 Generic functions](#-generic-functions)
+- [📃 Log](#-log)
 - [🧬 Middlewares](#-middlewares)
   - [CORS](#cors)
   - [CSRF](#csrf)
   - [Session](#session)
+  - [Logger](#logger)
   - [Filesystem](#filesystem)
   - [Monitor](#monitor)
   - [Healthcheck](#healthcheck)
@@ -630,6 +632,12 @@ curl "http://localhost:3000/header"
 
 </details>
 
+## 📃 Log
+
+`fiber.AllLogger` interface now has a new method called `Logger`. This method can be used to get the underlying logger instance from the Fiber logger middleware. This is useful when you want to configure the logger middleware with a custom logger and still want to access the underlying logger instance.
+
+You can find more details about this feature in [/docs/api/log.md](./api/log.md#logger).
+
 ## 🧬 Middlewares
 
 ### Adaptor
@@ -705,6 +713,49 @@ The Session middleware has undergone key changes in v3 to improve functionality
 
 For more details on these changes and migration instructions, check the [Session Middleware Migration Guide](./middleware/session.md#migration-guide).
 
+### Logger
+
+New helper function called `LoggerToWriter` has been added to the logger middleware. This function allows you to use 3rd party loggers such as `logrus` or `zap` with the Fiber logger middleware without any extra afford. For example, you can use `zap` with Fiber logger middleware like this:
+
+<details>
+<summary>Example</summary>
+
+```go
+package main
+
+import (
+    "github.com/gofiber/contrib/fiberzap/v2"
+    "github.com/gofiber/fiber/v3"
+    "github.com/gofiber/fiber/v3/log"
+    "github.com/gofiber/fiber/v3/middleware/logger"
+)
+
+func main() {
+    // Create a new Fiber instance
+    app := fiber.New()
+
+    // Create a new zap logger which is compatible with Fiber AllLogger interface
+    zap := fiberzap.NewLogger(fiberzap.LoggerConfig{
+        ExtraKeys: []string{"request_id"},
+    })
+
+    // Use the logger middleware with zerolog logger
+    app.Use(logger.New(logger.Config{
+        Output: logger.LoggerToWriter(zap, log.LevelDebug),
+    }))
+
+    // Define a route
+    app.Get("/", func(c fiber.Ctx) error {
+        return c.SendString("Hello, World!")
+    })
+
+    // Start server on http://localhost:3000
+    app.Listen(":3000")
+}
+```
+
+</details>
+
 ### Filesystem
 
 We've decided to remove filesystem middleware to clear up the confusion between static and filesystem middleware.

log/default.go

@@ -210,6 +210,11 @@ func (l *defaultLogger) SetOutput(writer io.Writer) {
 	l.stdlog.SetOutput(writer)
 }
 
+// Logger returns the logger instance. It can be used to adjust the logger configurations in case of need.
+func (l *defaultLogger) Logger() any {
+	return l.stdlog
+}
+
 // DefaultLogger returns the default logger.
 func DefaultLogger() AllLogger {
 	return logger

log/default_test.go

@@ -221,6 +221,22 @@ func Test_SetLevel(t *testing.T) {
 	require.Equal(t, "[?8] ", setLogger.level.toString())
 }
 
+func Test_Logger(t *testing.T) {
+	underlyingLogger := log.New(os.Stderr, "", log.LstdFlags|log.Lshortfile|log.Lmicroseconds)
+	setLogger := &defaultLogger{
+		stdlog: underlyingLogger,
+		depth:  4,
+	}
+
+	require.Equal(t, underlyingLogger, setLogger.Logger())
+
+	logger, ok := setLogger.Logger().(*log.Logger)
+	require.True(t, ok)
+
+	logger.SetFlags(log.LstdFlags | log.Lshortfile | log.Lmicroseconds)
+	require.Equal(t, log.LstdFlags|log.Lshortfile|log.Lmicroseconds, setLogger.stdlog.Flags())
+}
+
 func Test_Debugw(t *testing.T) {
 	initDefaultLogger()
 

log/log.go

@@ -52,17 +52,27 @@ type CommonLogger interface {
 	WithLogger
 }
 
-// ControlLogger provides methods to config a logger.
-type ControlLogger interface {
+// ConfigurableLogger provides methods to config a logger.
+type ConfigurableLogger interface {
+	// SetLevel sets logging level.
+	//
+	// Available levels: Trace, Debug, Info, Warn, Error, Fatal, Panic.
 	SetLevel(level Level)
+
+	// SetOutput sets the logger output.
 	SetOutput(w io.Writer)
+
+	// Logger returns the logger instance. It can be used to adjust the logger configurations in case of need.
+	Logger() any
 }
 
-// AllLogger is the combination of Logger, FormatLogger, CtxLogger and ControlLogger.
+// AllLogger is the combination of Logger, FormatLogger, CtxLogger and ConfigurableLogger.
 // Custom extensions can be made through AllLogger
 type AllLogger interface {
 	CommonLogger
-	ControlLogger
+	ConfigurableLogger
+
+	// WithContext returns a new logger with the given context.
 	WithContext(ctx context.Context) CommonLogger
 }
 

middleware/logger/logger_test.go

@@ -1,3 +1,4 @@
+//nolint:depguard // Because we test logging :D
 package logger
 
 import (
@@ -6,15 +7,18 @@ import (
 	"errors"
 	"fmt"
 	"io"
+	"log"
 	"net/http"
 	"net/http/httptest"
 	"os"
 	"runtime"
+	"strconv"
 	"sync"
 	"testing"
 	"time"
 
 	"github.com/gofiber/fiber/v3"
+	fiberlog "github.com/gofiber/fiber/v3/log"
 	"github.com/gofiber/fiber/v3/middleware/requestid"
 	"github.com/stretchr/testify/require"
 	"github.com/valyala/bytebufferpool"
@@ -181,6 +185,83 @@ func Test_Logger_ErrorTimeZone(t *testing.T) {
 	require.Equal(t, fiber.StatusNotFound, resp.StatusCode)
 }
 
+// go test -run Test_Logger_Fiber_Logger
+func Test_Logger_LoggerToWriter(t *testing.T) {
+	app := fiber.New()
+
+	buf := bytebufferpool.Get()
+	t.Cleanup(func() {
+		bytebufferpool.Put(buf)
+	})
+
+	logger := fiberlog.DefaultLogger()
+	stdlogger, ok := logger.Logger().(*log.Logger)
+	require.True(t, ok)
+
+	stdlogger.SetFlags(0)
+	logger.SetOutput(buf)
+
+	testCases := []struct {
+		levelStr string
+		level    fiberlog.Level
+	}{
+		{
+			level:    fiberlog.LevelTrace,
+			levelStr: "Trace",
+		},
+		{
+			level:    fiberlog.LevelDebug,
+			levelStr: "Debug",
+		},
+		{
+			level:    fiberlog.LevelInfo,
+			levelStr: "Info",
+		},
+		{
+			level:    fiberlog.LevelWarn,
+			levelStr: "Warn",
+		},
+		{
+			level:    fiberlog.LevelError,
+			levelStr: "Error",
+		},
+	}
+
+	for _, tc := range testCases {
+		level := strconv.Itoa(int(tc.level))
+		t.Run(level, func(t *testing.T) {
+			buf.Reset()
+
+			app.Use("/"+level, New(Config{
+				Format: "${error}",
+				Output: LoggerToWriter(logger, tc.
+					level),
+			}))
+
+			app.Get("/"+level, func(_ fiber.Ctx) error {
+				return errors.New("some random error")
+			})
+
+			resp, err := app.Test(httptest.NewRequest(fiber.MethodGet, "/"+level, nil))
+			require.NoError(t, err)
+			require.Equal(t, fiber.StatusInternalServerError, resp.StatusCode)
+			require.Equal(t, "["+tc.levelStr+"] some random error\n", buf.String())
+		})
+
+		require.Panics(t, func() {
+			LoggerToWriter(logger, fiberlog.LevelPanic)
+		})
+
+		require.Panics(t, func() {
+			LoggerToWriter(logger, fiberlog.LevelFatal)
+		})
+
+		require.Panics(t, func() {
+			LoggerToWriter(nil, fiberlog.LevelFatal)
+		})
+	}
+}
+
 type fakeErrorOutput int
 
 func (o *fakeErrorOutput) Write([]byte) (int, error) {
@@ -733,6 +814,19 @@ func Benchmark_Logger(b *testing.B) {
 		benchmarkSetup(bb, app, "/")
 	})
 
+	b.Run("DefaultFormatWithFiberLog", func(bb *testing.B) {
+		app := fiber.New()
+		logger := fiberlog.DefaultLogger()
+		logger.SetOutput(io.Discard)
+		app.Use(New(Config{
+			Output: LoggerToWriter(logger, fiberlog.LevelDebug),
+		}))
+		app.Get("/", func(c fiber.Ctx) error {
+			return c.SendString("Hello, World!")
+		})
+		benchmarkSetup(bb, app, "/")
+	})
+
 	b.Run("WithTagParameter", func(bb *testing.B) {
 		app := fiber.New()
 		app.Use(New(Config{
@@ -876,6 +970,19 @@ func Benchmark_Logger_Parallel(b *testing.B) {
 		benchmarkSetupParallel(bb, app, "/")
 	})
 
+	b.Run("DefaultFormatWithFiberLog", func(bb *testing.B) {
+		app := fiber.New()
+		logger := fiberlog.DefaultLogger()
+		logger.SetOutput(io.Discard)
+		app.Use(New(Config{
+			Output: LoggerToWriter(logger, fiberlog.LevelDebug),
+		}))
+		app.Get("/", func(c fiber.Ctx) error {
+			return c.SendString("Hello, World!")
+		})
+		benchmarkSetupParallel(bb, app, "/")
+	})
+
 	b.Run("DefaultFormatDisableColors", func(bb *testing.B) {
 		app := fiber.New()
 		app.Use(New(Config{