Logging

Contextual Logging

• Contextual Logging Design

package logger

import (
    "context"

    "go.uber.org/zap"
    "go.uber.org/zap/zapcore"
    "golang.org/x/exp/maps"
)

type filedsMapKey struct{}

var zConfig zap.Config

func init() {
    var l *zap.Logger
    zConfig = zap.NewProductionConfig()
    zConfig.EncoderConfig.TimeKey = "time"
    zConfig.DisableStacktrace = true
    l, _ = zConfig.Build()
    defer l.Sync()
    zap.ReplaceGlobals(l)
}

func SetLevel(level zapcore.Level) {
    zConfig.Level.SetLevel(level)
}

func Logger(ctx context.Context) *zap.Logger {
    fs := Fields(ctx)
    if fs == nil {
        return zap.L()
    }

    return zap.L().With(fs...)
}

func WithFields(ctx context.Context, fields ...zap.Field) context.Context {
    v := ctx.Value(filedsMapKey{})
    if v == nil {
        fm := make(map[string]zap.Field, len(fields))
        for _, f := range fields {
            fm[f.Key] = f
        }
        return context.WithValue(ctx, filedsMapKey{}, fm)
    }

    fm := v.(map[string]zap.Field)
    for _, f := range fields {
        fm[f.Key] = f
    }

    return ctx
}

func Fields(ctx context.Context) []zap.Field {
    v := ctx.Value(filedsMapKey{})
    if v == nil {
        return nil
    }

    return maps.Values(v.(map[string]zap.Field))
}