logger.md

id
logger

Logger

Logger middleware for Fiber that logs HTTP request/response details.

Signatures

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

Examples

Import the middleware package that is part of the Fiber web framework

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

:::tip The order of registration plays a role. Only all routes that are registered after this one will be logged. The middleware should therefore be one of the first to be registered. :::

After you initiate your Fiber app, you can use the following possibilities:

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

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

// Logging Request ID
app.Use(requestid.New())
app.Use(logger.New(logger.Config{
    // For more options, see the Config section
    Format: "${pid} ${locals: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
file, err := os.OpenFile("./123.log", os.O_RDWR|os.O_CREATE|os.O_APPEND, 0666)
if err != nil {
    log.Fatalf("error opening file: %v", err)
}
defer file.Close()
app.Use(logger.New(logger.Config{
    Output: file,
}))

// 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,
}))

:::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. :::

Config

Config

Property	Type	Description	Default
Next	func(fiber.Ctx) bool	Next defines a function to skip this middleware when returned true.	nil
Done	func(fiber.Ctx, []byte)	Done is a function that is called after the log string for a request is written to Output, 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
Output	io.Writer	Output is a writer where logs are written.	os.Stdout
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)	-
timeZoneLocation	*time.Location	Internal field for the time zone location. (This is not a user-configurable field)	-

Default Config

var ConfigDefault = Config{
    Next:          nil,
    Done:          nil,
    Format:        "[${time}] ${ip} ${status} - ${latency} ${method} ${path} ${error}\n",
    TimeFormat:    "15:04:05",
    TimeZone:      "Local",
    TimeInterval:  500 * time.Millisecond,
    Output:        os.Stdout,
    DisableColors: false,
}

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"
    // DEPRECATED: Use TagReqHeader instead
    TagHeader            = "header:"        // request header
    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"
)