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slog: Fiber middleware

tag Go Version GoDoc Build Status Go report Coverage Contributors License

Fiber middleware to log http requests using slog.

See also:

HTTP middlewares:

Loggers:

Log sinks:

πŸš€ Install

# Fiber v2 (current)
go get github.com/samber/slog-fiber

# Fiber v3 (beta)
go get github.com/samber/slog-fiber@fiber-v3

Compatibility: go >= 1.21

No breaking changes will be made to exported APIs before v2.0.0.

πŸ’‘ Usage

Handler options

type Config struct {
	DefaultLevel     slog.Level
	ClientErrorLevel slog.Level
	ServerErrorLevel slog.Level

	WithUserAgent      bool
	WithRequestID      bool
	WithRequestBody    bool
	WithRequestHeader  bool
	WithResponseBody   bool
	WithResponseHeader bool
	WithSpanID         bool
	WithTraceID        bool

	Filters []Filter
}

Attributes will be injected in log payload.

Other global parameters:

slogfiber.TraceIDKey = "trace_id"
slogfiber.SpanIDKey = "span_id"
slogfiber.RequestBodyMaxSize  = 64 * 1024 // 64KB
slogfiber.ResponseBodyMaxSize = 64 * 1024 // 64KB
slogfiber.HiddenRequestHeaders = map[string]struct{}{ ... }
slogfiber.HiddenResponseHeaders = map[string]struct{}{ ... }
slogfiber.RequestIDHeaderKey = "X-Request-Id"

Minimal

import (
	"github.com/gofiber/fiber/v2"
	"github.com/gofiber/fiber/v2/middleware/recover"
	slogfiber "github.com/samber/slog-fiber"
	"log/slog"
)

// Create a slog logger, which:
//   - Logs to stdout.
logger := slog.New(slog.NewTextHandler(os.Stdout, nil))

app := fiber.New()

app.Use(slogfiber.New(logger))
app.Use(recover.New())

app.Get("/", func(c *fiber.Ctx) error {
	return c.SendString("Hello, World πŸ‘‹!")
})

app.Listen(":4242")

// output:
// time=2023-10-15T20:32:58.926+02:00 level=INFO msg="Incoming request" env=production request.time=2023-10-15T20:32:58.626+02:00 request.method=GET request.path=/ request.route="" request.ip=127.0.0.1:63932 request.length=0 response.time=2023-10-15T20:32:58.926+02:00 response.latency=100ms response.status=200 response.length=7 id=229c7fc8-64f5-4467-bc4a-940700503b0d

OTEL

logger := slog.New(slog.NewTextHandler(os.Stdout, nil))

config := slogfiber.Config{
	WithSpanID:  true,
	WithTraceID: true,
}

app := fiber.New()
app.Use(slogfiber.NewWithConfig(logger, config))

Custom log levels

logger := slog.New(slog.NewTextHandler(os.Stdout, nil))

config := slogfiber.Config{
	DefaultLevel:     slog.LevelInfo,
	ClientErrorLevel: slog.LevelWarn,
	ServerErrorLevel: slog.LevelError,
}

app := fiber.New()
app.Use(slogfiber.NewWithConfig(logger, config))

Verbose

logger := slog.New(slog.NewTextHandler(os.Stdout, nil))

config := slogfiber.Config{
	WithRequestBody: true,
	WithResponseBody: true,
	WithRequestHeader: true,
	WithResponseHeader: true,
}

app := fiber.New()
app.Use(slogfiber.NewWithConfig(logger, config))

Filters

logger := slog.New(slog.NewTextHandler(os.Stdout, nil))

app := fiber.New()
app.Use(
	slogfiber.NewWithFilters(
		logger,
		slogfiber.Accept(func (c *fiber.Ctx) bool {
			return xxx
		}),
		slogfiber.IgnoreStatus(401, 404),
	),
)
app.Use(recover.New())

Available filters:

  • Accept / Ignore
  • AcceptMethod / IgnoreMethod
  • AcceptStatus / IgnoreStatus
  • AcceptStatusGreaterThan / IgnoreStatusLessThan
  • AcceptStatusGreaterThanOrEqual / IgnoreStatusLessThanOrEqual
  • AcceptPath / IgnorePath
  • AcceptPathContains / IgnorePathContains
  • AcceptPathPrefix / IgnorePathPrefix
  • AcceptPathSuffix / IgnorePathSuffix
  • AcceptPathMatch / IgnorePathMatch
  • AcceptHost / IgnoreHost
  • AcceptHostContains / IgnoreHostContains
  • AcceptHostPrefix / IgnoreHostPrefix
  • AcceptHostSuffix / IgnoreHostSuffix
  • AcceptHostMatch / IgnoreHostMatch

Using custom time formatters

// Create a slog logger, which:
//   - Logs to stdout.
//   - RFC3339 with UTC time format.
logger := slog.New(
	slogformatter.NewFormatterHandler(
		slogformatter.TimezoneConverter(time.UTC),
		slogformatter.TimeFormatter(time.RFC3339, nil),
	)(
		slog.NewTextHandler(os.Stdout, nil),
	),
)

app := fiber.New()

app.Use(slogfiber.New(logger))
app.Use(recover.New())

app.Get("/", func(c *fiber.Ctx) error {
	return c.SendString("Hello, World πŸ‘‹!")
})

app.Listen(":4242")

// output:
// time=2023-10-15T20:32:58.926+02:00 level=INFO msg="Incoming request" env=production request.time=2023-10-15T20:32:58Z request.method=GET request.path=/ request.route="" request.ip=127.0.0.1:63932 request.length=0 response.time=2023-10-15T20:32:58Z response.latency=100ms response.status=200 response.length=7 id=229c7fc8-64f5-4467-bc4a-940700503b0d

Using custom logger sub-group

logger := slog.New(slog.NewTextHandler(os.Stdout, nil))

app := fiber.New()

app.Use(slogfiber.New(logger.WithGroup("http")))
app.Use(recover.New())

app.Get("/", func(c *fiber.Ctx) error {
	return c.SendString("Hello, World πŸ‘‹!")
})

app.Listen(":4242")

// output:
// time=2023-10-15T20:32:58.926+02:00 level=INFO msg="Incoming request" env=production http.request.time=2023-10-15T20:32:58.626+02:00 http.request.method=GET http.request.path=/ http.request.route="" http.request.ip=127.0.0.1:63932 http.request.length=0 http.response.time=2023-10-15T20:32:58.926+02:00 http.response.latency=100ms http.response.status=200 http.response.length=7 http.id=229c7fc8-64f5-4467-bc4a-940700503b0d

Add logger to a single route

logger := slog.New(slog.NewTextHandler(os.Stdout, nil))

app := fiber.New()

app.Use(recover.New())

app.Get("/", slogfiber.New(logger), func(c *fiber.Ctx) error {
	return c.SendString("Hello, World πŸ‘‹!")
})

app.Listen(":4242")

Adding custom attributes

logger := slog.New(slog.NewTextHandler(os.Stdout, nil))

// Add an attribute to all log entries made through this logger.
logger = logger.With("env", "production")

app := fiber.New()

app.Use(slogfiber.New(logger))
app.Use(recover.New())

app.Get("/", func(c *fiber.Ctx) error {
	// Add an attribute to a single log entry.
	slogfiber.AddCustomAttributes(c, slog.String("foo", "bar"))
	return c.SendString("Hello, World πŸ‘‹!")
})

app.Listen(":4242")

// output:
// time=2023-10-15T20:32:58.926+02:00 level=INFO msg="Incoming request" env=production request.time=2023-10-15T20:32:58.626+02:00 request.method=GET request.path=/ request.route="" request.ip=127.0.0.1:63932 request.length=0 response.time=2023-10-15T20:32:58.926+02:00 response.latency=100ms response.status=200 response.length=7 id=229c7fc8-64f5-4467-bc4a-940700503b0d foo=bar

JSON output

logger := slog.New(slog.NewJSONHandler(os.Stdout, nil)),

app := fiber.New()

app.Use(slogfiber.New(logger))
app.Use(recover.New())

app.Get("/", func(c *fiber.Ctx) error {
	return c.SendString("Hello, World πŸ‘‹!")
})

app.Listen(":4242")

// output:
// {"time":"2023-10-15T20:32:58.926+02:00","level":"INFO","msg":"Incoming request","env":"production","http":{"request":{"time":"2023-10-15T20:32:58.626+02:00","method":"GET","path":"/","route":"","ip":"127.0.0.1:55296","length":0},"response":{"time":"2023-10-15T20:32:58.926+02:00","latency":100000,"status":200,"length":7},"id":"04201917-d7ba-4b20-a3bb-2fffba5f2bd9"}}

🀝 Contributing

Don't hesitate ;)

# Install some dev dependencies
make tools

# Run tests
make test
# or
make watch-test

πŸ‘€ Contributors

Contributors

πŸ’« Show your support

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πŸ“ License

Copyright Β© 2023 Samuel Berthe.

This project is MIT licensed.