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zapとzerologをlumberjackと組み合わせてログローテーションする

Last updated at Posted at 2022-12-18

はじめに

今回の記事では、高速なロギングライブラリであるzap、zerologと豊富なログローテーション機能を持つlumberjackライブラリを組み合わせる方法を紹介しようと思います。

lumberjackの設定項目

lumberjackでは以下の項目でログローテーションを制御できます。

  • ログファイルのパス
  • ローテーションサイズ(メガバイト単位)
  • 最長保持期間(日単位)
  • 最大保持数
  • ログの日時情報にローカル時刻を利用するかUTCを利用するか
  • ローテーション後にgzipで圧縮するか

type Logger struct {
	// Filename is the file to write logs to.  Backup log files will be retained
	// in the same directory.  It uses <processname>-lumberjack.log in
	// os.TempDir() if empty.
	Filename string `json:"filename" yaml:"filename"`

	// MaxSize is the maximum size in megabytes of the log file before it gets
	// rotated. It defaults to 100 megabytes.
	MaxSize int `json:"maxsize" yaml:"maxsize"`

	// MaxAge is the maximum number of days to retain old log files based on the
	// timestamp encoded in their filename.  Note that a day is defined as 24
	// hours and may not exactly correspond to calendar days due to daylight
	// savings, leap seconds, etc. The default is not to remove old log files
	// based on age.
	MaxAge int `json:"maxage" yaml:"maxage"`

	// MaxBackups is the maximum number of old log files to retain.  The default
	// is to retain all old log files (though MaxAge may still cause them to get
	// deleted.)
	MaxBackups int `json:"maxbackups" yaml:"maxbackups"`

	// LocalTime determines if the time used for formatting the timestamps in
	// backup files is the computer's local time.  The default is to use UTC
	// time.
	LocalTime bool `json:"localtime" yaml:"localtime"`

	// Compress determines if the rotated log files should be compressed
	// using gzip. The default is not to perform compression.
	Compress bool `json:"compress" yaml:"compress"`
	// contains filtered or unexported fields
}

zap ✖️ lumberjack

zapとlumberjackを連携させるには、zapcore.WriteSyncerを利用します。

package main

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

func main() {
	sink := zapcore.AddSync(&lumberjack.Logger{
		Filename:   "logs/zap.log",
		MaxSize:    10,
		MaxBackups: 10,
		MaxAge:     10,
		Compress:   true,
	})
	core := zapcore.NewCore(
		zapcore.NewJSONEncoder(zap.NewProductionEncoderConfig()),
		sink,
		zap.InfoLevel,
	)
	logger := zap.New(core)
	logger.Info("hoge")
}

出力されるログファイルは以下になります。

{"level":"info","ts":1671340569.6598823,"msg":"hoge"}

zerolog ✖️ lumberjack

zapの場合はLogger生成時にlumberjackで作成したWriterを渡すだけなのでかなりシンプルです。

package main

import (
	"github.com/rs/zerolog"
	"github.com/rs/zerolog/log"
	"gopkg.in/natefinch/lumberjack.v2"
)

func main() {
	writer := &lumberjack.Logger{
		Filename:   "logs/zerolog.log",
		MaxSize:    10,
		MaxBackups: 10,
		MaxAge:     10,
		Compress:   true,
	}

	log.Logger = zerolog.New(writer).With().Timestamp().Logger()
	log.Info().Msg("hoge")
}

出力されるログファイルは以下になります。

{"level":"info","time":"2022-12-18T05:17:56Z","message":"hoge"}
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