slog: Syslog handler

A Syslog Handler for slog Go library.

---

^{Sponsored by:}

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

---

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.