fiber/docs/middleware/logger.md

id

id
logger

Logger

Logger middleware for Fiber that logs HTTP requests and responses.

Signatures

func New(config ...Config) fiber.Handler

Examples

Import the package:

import (
    "github.com/gofiber/fiber/v3"
    "github.com/gofiber/fiber/v3/middleware/logger"
)

:::tip Registration order matters: only routes added after the logger are logged, so register it early. :::

Once your Fiber app is initialized, use the middleware like this:

// Initialize default config
app.Use(logger.New())

// Or extend your config for customization
// Log remote IP and port
app.Use(logger.New(logger.Config{
    Format: "[${ip}]:${port} ${status} - ${method} ${path}\n",
}))

// Logging Request ID
app.Use(requestid.New()) // Ensure requestid middleware is used before the logger
app.Use(logger.New(logger.Config{
    CustomTags: map[string]logger.LogFunc{
        "requestid": func(output logger.Buffer, c fiber.Ctx, data *logger.Data, extraParam string) (int, error) {
            return output.WriteString(requestid.FromContext(c))
        },
    },
    // For more options, see the Config section
    // Use the custom tag ${requestid} as defined above.
    Format: "${pid} ${requestid} ${status} - ${method} ${path}\n",
}))

// Changing TimeZone & TimeFormat
app.Use(logger.New(logger.Config{
    Format:     "${pid} ${status} - ${method} ${path}\n",
    TimeFormat: "02-Jan-2006",
    TimeZone:   "America/New_York",
}))

// Custom File Writer
accessLog, err := os.OpenFile("./access.log", os.O_RDWR|os.O_CREATE|os.O_APPEND, 0666)
if err != nil {
    log.Fatalf("error opening access.log file: %v", err)
}
defer accessLog.Close()
app.Use(logger.New(logger.Config{
    Stream: accessLog,
}))

// Add Custom Tags
app.Use(logger.New(logger.Config{
    CustomTags: map[string]logger.LogFunc{
        "custom_tag": func(output logger.Buffer, c fiber.Ctx, data *logger.Data, extraParam string) (int, error) {
            return output.WriteString("it is a custom tag")
        },
    },
}))

// Callback after log is written
app.Use(logger.New(logger.Config{
    TimeFormat: time.RFC3339Nano,
    TimeZone:   "Asia/Shanghai",
    Done: func(c fiber.Ctx, logString []byte) {
        if c.Response().StatusCode() != fiber.StatusOK {
            reporter.SendToSlack(logString)
        }
    },
}))

// Disable colors when outputting to default format
app.Use(logger.New(logger.Config{
    DisableColors: true,
}))

// Force the use of colors
app.Use(logger.New(logger.Config{
    ForceColors: true,
}))

// Use predefined formats
app.Use(logger.New(logger.Config{
    Format: logger.CommonFormat,
}))

app.Use(logger.New(logger.Config{
    Format: logger.CombinedFormat,
}))

app.Use(logger.New(logger.Config{
    Format: logger.JSONFormat,
}))

app.Use(logger.New(logger.Config{
    Format: logger.ECSFormat,
}))

Use Logger Middleware with Other Loggers

To combine the logger middleware with loggers like Zerolog, Zap, or Logrus, use the LoggerToWriter helper to adapt them to an io.Writer.

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 the zap logger
    app.Use(logger.New(logger.Config{
        Stream: 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 custom streams may require locking to serialize writes. :::

Config

Property	Type	Description	Default
Next	func(fiber.Ctx) bool	Next defines a function to skip this middleware when it returns 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, or create your own using Tags.	[${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
ForceColors	bool	ForceColors defines if the logs output should be colorized even when the output is not a terminal.	false

Default Config

var ConfigDefault = Config{
    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

// Logger variables
const (
    TagPid               = "pid"
    TagTime              = "time"
    TagReferer           = "referer"
    TagProtocol          = "protocol"
    TagPort              = "port"
    TagIP                = "ip"
    TagIPs               = "ips"
    TagHost              = "host"
    TagMethod            = "method"
    TagPath              = "path"
    TagURL               = "url"
    TagUA                = "ua"
    TagLatency           = "latency"
    TagStatus            = "status"         // response status
    TagResBody           = "resBody"        // response body
    TagReqHeaders        = "reqHeaders"
    TagQueryStringParams = "queryParams"    // request query parameters
    TagBody              = "body"           // request body
    TagBytesSent         = "bytesSent"
    TagBytesReceived     = "bytesReceived"
    TagRoute             = "route"
    TagError             = "error"
    TagReqHeader         = "reqHeader:"     // request header
    TagRespHeader        = "respHeader:"    // response header
    TagQuery             = "query:"         // request query
    TagForm              = "form:"          // request form
    TagCookie            = "cookie:"        // request cookie
    TagLocals            = "locals:"
    // colors
    TagBlack             = "black"
    TagRed               = "red"
    TagGreen             = "green"
    TagYellow            = "yellow"
    TagBlue              = "blue"
    TagMagenta           = "magenta"
    TagCyan              = "cyan"
    TagWhite             = "white"
    TagReset             = "reset"
)