slog: Fluentd handler
A Fluentd Handler for slog Go library.
See also:
HTTP middlewares:
Loggers:
Log sinks:
🚀 Install
go get github.com/samber/slog-fluentd/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-fluentd/v2
Fluentd settings
<source>
@type forward
bind 0.0.0.0
port 24224
</source>
Handler options
type Option struct {
// log level (default: debug)
Level slog.Leveler
// connection to Fluentd
Client *fluentd.Fluentd
Tag string
// optional: customize json payload builder
Converter Converter
// 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.
Fluentd tag
can be inserted in logger options or in a record attribute of type string.
Other global parameters:
slogfluentd.SourceKey = "source"
slogfluentd.ContextKey = "extra"
slogfluentd.ErrorKeys = []string{"error", "err"}
Example
import (
"github.com/fluent/fluent-logger-golang/fluent"
slogfluentd "github.com/samber/slog-fluentd/v2"
"log/slog"
)
func main() {
// docker-compose up -d
client, err := fluent.New(fluent.Config{
FluentHost: "localhost",
FluentPort: 24224,
FluentNetwork: "tcp",
MarshalAsJSON: true,
Async: true,
})
if err != nil {
log.Fatal(err.Error())
}
logger := slog.New(
slogfluentd.Option{
Level: slog.LevelDebug,
Client: client,
Tag: "api",
}.NewFluentdHandler(),
)
logger = logger.
With("environment", "dev").
With("release", "v1.0.0")
// log error
logger.
With("tag", "api.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:
// tag: api.sql
{
"timestamp":"2023-04-10T14:00:0.000000+00:00",
"level":"ERROR",
"message":"caramba!",
"tag":"api.sql",
"error":{
"error":"could not count users",
"kind":"*errors.errorString",
"stack":null
},
"extra":{
"environment":"dev",
"release":"v1.0.0",
"query.statement":"SELECT COUNT(*) FROM users;",
"query.duration": "1s"
}
}
// tag: api
{
"timestamp":"2023-04-10T14:00:0.000000+00:00",
"level":"INFO",
"message":"user registration",
"tag":"api",
"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 (
slogfluentd "github.com/samber/slog-fluentd"
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(
slogfluentd.Option{
// ...
AttrFromContext: []func(ctx context.Context) []slog.Attr{
slogotel.ExtractOtelAttrFromContext([]string{"tracing"}, "trace_id", "span_id"),
},
}.NewFluentdHandler(),
)
logger.ErrorContext(ctx, "a message")
}
🤝 Contributing
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.