slog: Syslog handler

A Syslog Handler for slog Go library.

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^{Sponsored by:}

Cloud-native search engine for observability - An OSS alternative to Splunk, Elasticsearch, Loki, and Tempo.

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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
• slog-mock: slog.Handler for test purposes

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-syslog/v2

Compatibility: go >= 1.21

No breaking changes will be made to exported APIs before v3.0.0.

💡 Usage

GoDoc: https://pkg.go.dev/github.com/samber/slog-syslog/v2

Handler options

type Option struct {
	// log level (default: debug)
	Level slog.Leveler

	// connection to syslog server
	Writer *syslog.Writer

	// optional: customize json payload builder
	Converter Converter
	// optional: custom marshaler
	Marshaler func(v any) ([]byte, error)
	// optional: fetch attributes from context
	AttrFromContext []func(ctx context.Context) []slog.Attr

	// optional: see slog.HandlerOptions
	AddSource   bool
	ReplaceAttr func(groups []string, a slog.Attr) slog.Attr
}

Attributes will be injected in log payload.

Other global parameters:

slogsyslog.SourceKey = "source"
slogsyslog.ContextKey = "extra"
slogsyslog.ErrorKeys = []string{"error", "err"}

Example

import (
	"fmt"
	"log"
	"log/slog"
	"net"
	"time"

	slogsyslog "github.com/samber/slog-syslog/v2"
)

func main() {
	// ncat -u -l 9999 -k
	writer, err := net.Dial("udp", "localhost:9999")
	if err != nil {
		log.Fatal(err)
	}

	logger := slog.New(slogsyslog.Option{Level: slog.LevelDebug, Writer: writer}.NewSyslogHandler())
	logger = logger.
		With("environment", "dev").
		With("release", "v1.0.0")

	// log error
	logger.
		With("category", "sql").
		With("query.statement", "SELECT COUNT(*) FROM users;").
		With("query.duration", 1*time.Second).
		With("error", fmt.Errorf("could not count users")).
		Error("caramba!")

	// log user signup
	logger.
		With(
			slog.Group("user",
				slog.String("id", "user-123"),
				slog.Time("created_at", time.Now()),
			),
		).
		Info("user registration")
}

Output:

@cee: {"timestamp":"2023-04-10T14:00:0.000000", "level":"ERROR", "message":"caramba!", "error":{ "error":"could not count users", "kind":"*errors.errorString", "stack":null }, "extra":{ "environment":"dev", "release":"v1.0.0", "category":"sql", "query.statement":"SELECT COUNT(*) FROM users;", "query.duration": "1s" }}

@cee: {"timestamp":"2023-04-10T14:00:0.000000", "level":"INFO", "message":"user registration", "error":null, "extra":{ "environment":"dev", "release":"v1.0.0", "user":{ "id":"user-123", "created_at":"2023-04-10T14:00:0.000000+00:00"}}}

Tracing

Import the samber/slog-otel library.

import (
	slogsyslog "github.com/samber/slog-syslog"
	slogotel "github.com/samber/slog-otel"
	"go.opentelemetry.io/otel/sdk/trace"
)

func main() {
	tp := trace.NewTracerProvider(
		trace.WithSampler(trace.AlwaysSample()),
	)
	tracer := tp.Tracer("hello/world")

	ctx, span := tracer.Start(context.Background(), "foo")
	defer span.End()

	span.AddEvent("bar")

	logger := slog.New(
		slogsyslog.Option{
			// ...
			AttrFromContext: []func(ctx context.Context) []slog.Attr{
				slogotel.ExtractOtelAttrFromContext([]string{"tracing"}, "trace_id", "span_id"),
			},
		}.NewSyslogHandler(),
	)

	logger.ErrorContext(ctx, "a message")
}

🤝 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

👤 Contributors

💫 Show your support

Give a ⭐️ if this project helped you!

📝 License

Copyright © 2023 Samuel Berthe.

This project is MIT licensed.