slog: Gin middleware

Gin middleware to log http requests using slog.

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See also:

slog-multi: slog.Handler chaining, fanout, routing, failover, load balancing...
slog-formatter: slog attribute formatting
slog-sampling: slog sampling policy

HTTP middlewares:

slog-gin: Gin middleware for slog logger
slog-echo: Echo middleware for slog logger
slog-fiber: Fiber middleware for slog logger
slog-chi: Chi middleware for slog logger
slog-http: net/http middleware for slog logger

Loggers:

slog-zap: A slog handler for Zap
slog-zerolog: A slog handler for Zerolog
slog-logrus: A slog handler for Logrus

Log sinks:

slog-datadog: A slog handler for Datadog
slog-betterstack: A slog handler for Betterstack
slog-rollbar: A slog handler for Rollbar
slog-loki: A slog handler for Loki
slog-sentry: A slog handler for Sentry
slog-syslog: A slog handler for Syslog
slog-logstash: A slog handler for Logstash
slog-fluentd: A slog handler for Fluentd
slog-graylog: A slog handler for Graylog
slog-quickwit: A slog handler for Quickwit
slog-slack: A slog handler for Slack
slog-telegram: A slog handler for Telegram
slog-mattermost: A slog handler for Mattermost
slog-microsoft-teams: A slog handler for Microsoft Teams
slog-webhook: A slog handler for Webhook
slog-kafka: A slog handler for Kafka
slog-nats: A slog handler for NATS
slog-parquet: A slog handler for Parquet + Object Storage
slog-channel: A slog handler for Go channels

🚀 Install

go get github.com/samber/slog-gin

Compatibility: go >= 1.21

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

💡 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:

sloggin.TraceIDKey = "trace-id"
sloggin.SpanIDKey = "span-id"
sloggin.RequestBodyMaxSize  = 64 * 1024 // 64KB
sloggin.ResponseBodyMaxSize = 64 * 1024 // 64KB
sloggin.HiddenRequestHeaders = map[string]struct{}{ ... }
sloggin.HiddenResponseHeaders = map[string]struct{}{ ... }
sloggin.RequestIDHeaderKey = "X-Request-Id"

Minimal

import (
	"github.com/gin-gonic/gin"
	sloggin "github.com/samber/slog-gin"
	"log/slog"
)

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

router := gin.New()

// Add the sloggin middleware to all routes.
// The middleware will log all requests attributes.
router.Use(sloggin.New(logger))
router.Use(gin.Recovery())

// Example pong request.
router.GET("/pong", func(c *gin.Context) {
    c.String(http.StatusOK, "pong")
})

router.Run(":1234")

// 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.query="" 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=""

OTEL

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

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

router := gin.New()
router.Use(sloggin.NewWithConfig(logger, config))

Custom log levels

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

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

router := gin.New()
router.Use(sloggin.NewWithConfig(logger, config))

Verbose

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

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

router := gin.New()
router.Use(sloggin.NewWithConfig(logger, config))

Filters

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

router := gin.New()
router.Use(
	sloggin.NewWithFilters(
		logger,
		sloggin.Accept(func (c *gin.Context) bool {
			return xxx
		}),
		sloggin.IgnoreStatus(401, 404),
	),
)

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

import (
	"github.com/gin-gonic/gin"
	sloggin "github.com/samber/slog-gin"
	slogformatter "github.com/samber/slog-formatter"
	"log/slog"
)

// 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.DateTime, nil),
    )(
        slog.NewTextHandler(os.Stdout, nil),
    ),
)

router := gin.New()

// Add the sloggin middleware to all routes.
// The middleware will log all requests attributes.
router.Use(sloggin.New(logger))
router.Use(gin.Recovery())

// Example pong request.
router.GET("/pong", func(c *gin.Context) {
    c.String(http.StatusOK, "pong")
})

router.Run(":1234")

// 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.query="" 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=""

Using custom logger sub-group

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

router := gin.New()

// Add the sloggin middleware to all routes.
// The middleware will log all requests attributes under a "http" group.
router.Use(sloggin.New(logger.WithGroup("http")))
router.Use(gin.Recovery())

// Example pong request.
router.GET("/pong", func(c *gin.Context) {
    c.String(http.StatusOK, "pong")
})

router.Run(":1234")

// 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=/ request.query="" 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=""

Add logger to a single route

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

router := gin.New()
router.Use(gin.Recovery())

// Example pong request.
// Add the sloggin middleware to a single routes.
router.GET("/pong", sloggin.New(logger), func(c *gin.Context) {
    c.String(http.StatusOK, "pong")
})

router.Run(":1234")

Adding custom attributes

logger := slog.New(slog.NewTextHandler(os.Stdout, nil)).
    With("environment", "production").
    With("server", "gin/1.9.0").
    With("server_start_time", time.Now()).
    With("gin_mode", gin.EnvGinMode)

router := gin.New()

// Add the sloggin middleware to all routes.
// The middleware will log all requests attributes.
router.Use(sloggin.New(logger))
router.Use(gin.Recovery())

// Example pong request.
router.GET("/pong", func(c *gin.Context) {
	// Add an attribute to a single log entry.
	sloggin.AddCustomAttributes(c, slog.String("foo", "bar"))
    c.String(http.StatusOK, "pong")
})

router.Run(":1234")

// output:
// time=2023-10-15T20:32:58.926+02:00 level=INFO msg="Incoming request" environment=production server=gin/1.9.0 gin_mode=release request.time=2023-10-15T20:32:58.626+02:00 request.method=GET request.path=/ request.query="" 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="" foo=bar

JSON output

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

router := gin.New()

// Add the sloggin middleware to all routes.
// The middleware will log all requests attributes.
router.Use(sloggin.New(logger))
router.Use(gin.Recovery())

// Example pong request.
router.GET("/pong", func(c *gin.Context) {
    c.String(http.StatusOK, "pong")
})

router.Run(":1234")

// output:
// {"time":"2023-10-15T20:32:58.926+02:00","level":"INFO","msg":"Incoming request","gin_mode":"GIN_MODE","env":"production","http":{"request":{"time":"2023-10-15T20:32:58.626+02:00","method":"GET","path":"/","query":"","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":""}}

🤝 Contributing

Ping me on twitter @samuelberthe (DMs, mentions, whatever :))
Fork the project
Fix open issues or request new features

Don't hesitate ;)

# Install some dev dependencies
make tools

# Run tests
make test
# or
make watch-test

Fleezesd/slog-gin