log using uber zap and lumberjack

logger.go

// 2021.7.2 UPDATE
// According to zap's doc, now we can use zapcore.AddSync to directly add lumberjack as a zap sync
// see https://github.com/uber-go/zap/blob/master/FAQ.md#does-zap-support-log-rotation

// thanks to:
// https://studygolang.com/articles/17394
// https://stackoverflow.com/questions/54395407/zap-logging-with-1-customized-config-and-2-lumberjack
package logger

import (
	"fmt"
	"net/url"

	"go.uber.org/zap"
	"go.uber.org/zap/zapcore"
	lumberjack "gopkg.in/natefinch/lumberjack.v2"
)

const (
	// DPanic, Panic and Fatal level can not be set by user
	DebugLevelStr   string = "debug"
	InfoLevelStr    string = "info"
	WarningLevelStr string = "warning"
	ErrorLevelStr   string = "error"
)

var (
	globalLogger *zap.Logger
	devMode      bool = false
)

type lumberjackSink struct {
	*lumberjack.Logger
}

func (lumberjackSink) Sync() error {
	return nil
}

func Init(logLevel string, logFile string, dev bool) error {
	devMode = dev
	var level zapcore.Level
	switch logLevel {
	case DebugLevelStr:
		level = zap.DebugLevel
	case InfoLevelStr:
		level = zap.InfoLevel
	case WarningLevelStr:
		level = zap.WarnLevel
	case ErrorLevelStr:
		level = zap.ErrorLevel
	default:
		return fmt.Errorf("unknown log level %s", logLevel)
	}
	encoderConfig := zapcore.EncoderConfig{
		TimeKey:        "ts",
		LevelKey:       "level",
		NameKey:        "logger",
		CallerKey:      "caller",
		MessageKey:     "msg",
		StacktraceKey:  "stacktrace",
		LineEnding:     zapcore.DefaultLineEnding,
		EncodeLevel:    zapcore.LowercaseLevelEncoder,
		EncodeTime:     zapcore.ISO8601TimeEncoder,
		EncodeDuration: zapcore.SecondsDurationEncoder,
		EncodeCaller:   zapcore.ShortCallerEncoder,
	}
	ll := lumberjack.Logger{
		Filename:   logFile,
		MaxSize:    1024, //MB
		MaxBackups: 30,
		MaxAge:     90, //days
		Compress:   true,
	}
	zap.RegisterSink("lumberjack", func(*url.URL) (zap.Sink, error) {
		return lumberjackSink{
			Logger: &ll,
		}, nil
	})
	loggerConfig := zap.Config{
		Level:         zap.NewAtomicLevelAt(level),
		Development:   dev,
		Encoding:      "console",
		EncoderConfig: encoderConfig,
		OutputPaths:   []string{fmt.Sprintf("lumberjack:%s", logFile)},
	}
	_globalLogger, err := loggerConfig.Build()
	if err != nil {
		panic(fmt.Sprintf("build zap logger from config error: %v", err))
	}
	zap.ReplaceGlobals(_globalLogger)
	globalLogger = _globalLogger
	return nil
}

func NewSugar(name string) *zap.SugaredLogger {
	return globalLogger.Named(name).Sugar()
}

• original post from
• refer comment about changed

Nice and cool script saved my time.👍

But globalLogger in line 87 will not be assigned as global variable globalLogger in line 28.

It just shadowing now, and cause panic at here, due to s.base is nil.

It sould be

func Init(logLevel string, logFile string, dev bool) error {
    // ...
    _globalLogger, err := loggerConfig.Build()
	if err != nil {
		panic(fmt.Sprintf("build zap logger from config error: %v", err))
	}
	zap.ReplaceGlobals(_globalLogger)
    globalLogger = _globalLogger
	return nil
}

Isn't it?