otelslog

README

OpenTelemetry handler

log/slog handler attaching OpenTelemetry trace details to logs.

Installation

go get github.com/go-slog/otelslog

Usage

Wrap an existing handler:

import(
    "log/slog"

    "github.com/go-slog/otelslog"
)

var handler slog.Handler

// Set up your handler
// handler = ...

// Wrap Handler
handler = otelslog.NewHandler(handler)

logger := slog.New(handler)

// Call logger with a context

logger.InfoContext(ctx, "hello world")

// Output: level=INFO msg="hello world" trace_id=74726163655f69645f74657374313233 span_id=7370616e5f696431

Use it as a middleware in slogmulti.Pipe:

import (
    "github.com/go-slog/otelslog"
    "github.com/samber/slog-multi"
)

handler = slogmulti.Pipe(otelslog.Middleware()).Handler(handler)

// Set p logger
// ...

Development

Run tests:

go test -race -v ./...

Run linter:

golangci-lint run

License

The project is licensed under the MIT License.

Documentation

Overview

Package otelslog provides an slog.Handler that attaches OpenTelemetry trace details to logs.

Package otelslog provides an slog.Handler that attaches OpenTelemetry trace details to logs.

Index

• func Middleware() func(slog.Handler) slog.Handler
• func NewHandler(handler slog.Handler) slog.Handler
• func ResourceMiddleware(res *resource.Resource) func(slog.Handler) slog.Handler
• func WithResource(handler slog.Handler, res *resource.Resource) slog.Handler
• type Handler
  • func (h Handler) Handle(ctx context.Context, record slog.Record) error
  • func (h Handler) WithAttrs(attrs []slog.Attr) slog.Handler
  • func (h Handler) WithGroup(name string) slog.Handler

Examples

• Handler
• WithResource

Functions

func Middleware

func Middleware() func(slog.Handler) slog.Handler

Middleware returns a Middleware for an slogmulti.Pipe handler.

func NewHandler

func NewHandler(handler slog.Handler) slog.Handler

NewHandler returns a new Handler.

func ResourceMiddleware

func ResourceMiddleware(res *resource.Resource) func(slog.Handler) slog.Handler

ResourceMiddleware returns a Middleware for an slogmulti.Pipe handler attaching resource attributes to an slog.Handler.

func WithResource

func WithResource(handler slog.Handler, res *resource.Resource) slog.Handler

WithResource returns an slog.Handler with all attributes attached from a resource.Resource.

Example

// Set up handler
handler := testHandler()

res, _ := resource.New(
	context.Background(),
	resource.WithAttributes(
		attribute.String("service.name", "my-service"),
		attribute.String("service.version", "1.0.0"),
		attribute.Bool("debug", false),
		attribute.Float64("sampling", 0.6),
	),
)

// Attach resource details to handler
handler = otelslog.WithResource(handler, res)

// Set up logger
logger := slog.New(handler)

// Call logger
logger.Info("hello world")

Output:

time=0001-01-01T00:00:00.000Z level=INFO msg="hello world" debug=false sampling=0.6 service.name=my-service service.version=1.0.0

Types

type Handler

type Handler struct {
	slog.Handler
}

Handler attaches details from an OpenTelemetry trace to each log record.

Example

package main

import (
	"context"
	"log/slog"
	"os"
	"time"

	"go.opentelemetry.io/otel/trace"

	"github.com/go-slog/otelslog"
)

func testHandler() slog.Handler {
	return slog.NewTextHandler(os.Stdout, &slog.HandlerOptions{
		AddSource: false,
		Level:     nil,
		ReplaceAttr: func(_ []string, a slog.Attr) slog.Attr {
			if a.Key == slog.TimeKey {
				a.Value = slog.TimeValue(time.Time{})
			}

			return a
		},
	})
}

func testContext() context.Context {
	ctx := context.Background()

	spanContext := trace.NewSpanContext(trace.SpanContextConfig{
		TraceID: [16]byte{116, 114, 97, 99, 101, 95, 105, 100, 95, 116, 101, 115, 116, 49, 50, 51},
		SpanID:  [8]byte{115, 112, 97, 110, 95, 105, 100, 49},
	})
	ctx = trace.ContextWithSpanContext(ctx, spanContext)

	return ctx
}

func main() {
	var handler slog.Handler

	// Set up handler
	handler = testHandler()

	// Wrap handler
	handler = otelslog.NewHandler(handler)

	// Set up logger
	logger := slog.New(handler)

	// later in some trace context (eg. http request)

	ctx := testContext()

	// Call logger with a context
	logger.InfoContext(ctx, "hello world")

}

Output:

time=0001-01-01T00:00:00.000Z level=INFO msg="hello world" trace_id=74726163655f69645f74657374313233 span_id=7370616e5f696431

func (Handler) Handle

func (h Handler) Handle(ctx context.Context, record slog.Record) error

Handle implements slog.Handler.

func (Handler) WithAttrs

func (h Handler) WithAttrs(attrs []slog.Attr) slog.Handler

WithAttrs implements slog.Handler.

func (Handler) WithGroup

func (h Handler) WithGroup(name string) slog.Handler

WithGroup implements slog.Handler.