logrus Transport

Wraps an existing *logrus.Logger. Map metadata flattens via Entry.WithFields; struct metadata lands under a configurable key.

go get go.loglayer.dev/transports/logrus

Basic Usage

import (
    "os"

    "github.com/sirupsen/logrus"

    "go.loglayer.dev"
    lllogrus "go.loglayer.dev/transports/logrus"
)

l := logrus.New()
l.Out = os.Stderr
l.Formatter = &logrus.JSONFormatter{}

log := loglayer.New(loglayer.Config{
    Transport: lllogrus.New(lllogrus.Config{Logger: l}),
})

log.Info("hello")
// {"level":"info","msg":"hello","time":"..."}

If you don't pass a Logger, the transport constructs one writing to Writer (default os.Stderr) at TraceLevel.

Config

type Config struct {
    transport.BaseConfig

    Logger            *logrus.Logger // wrap an existing logger
    Writer            io.Writer      // used only when Logger is nil
    MetadataFieldName string         // key for non-map metadata; default "metadata"
}

Fatal Behavior

logrus.Logger.Fatal and Logger.Log(FatalLevel, ...) call the logger's ExitFunc, which by default is os.Exit(1). To prevent logrus from exiting before the core's DisableFatalExit check can run, this transport always builds a fresh *logrus.Logger that copies the supplied logger's settings (Out, Hooks, Formatter, ReportCaller, Level, BufferPool) but with ExitFunc set to a no-op.

Two consequences:

• The user's original *logrus.Logger is never mutated; its ExitFunc is preserved.
• The wrapped copy returned by GetLoggerInstance is the no-op-ExitFunc version, not the original. For most operations this doesn't matter; configurations set on the original (formatter, hooks, etc.) are all preserved.

The core then decides whether os.Exit(1) is called after dispatch. See Fatal Exits the Process.

Metadata Handling

Map metadata → individual fields

log.WithMetadata(loglayer.Metadata{"requestId": "xyz", "n": 42}).Info("served")
// {"level":"info","msg":"served","n":42,"requestId":"xyz","time":"..."}

Each map entry becomes a key in logrus.Fields passed to WithFields.

Struct metadata → nested under MetadataFieldName

type User struct {
    ID   int    `json:"id"`
    Name string `json:"name"`
}

log.WithMetadata(User{ID: 7, Name: "Alice"}).Info("user")
// {"level":"info","metadata":{"id":7,"name":"Alice"},"msg":"user",...}

To use a different key per call, wrap in a map:

log.WithMetadata(loglayer.Metadata{"user": User{ID: 7, Name: "Alice"}}).Info("user")

Or globally via MetadataFieldName:

lllogrus.New(lllogrus.Config{
    Logger:            l,
    MetadataFieldName: "payload",
})

Reaching the Underlying Logger

GetLoggerInstance returns the wrapped (no-op-ExitFunc) *logrus.Logger:

l := log.GetLoggerInstance("logrus").(*logrus.Logger)
l.AddHook(myHook)

Level Mapping

LogLayer Level	logrus Level
LogLevelDebug	DebugLevel
LogLevelInfo	InfoLevel
LogLevelWarn	WarnLevel
LogLevelError	ErrorLevel
LogLevelFatal	FatalLevel