golang自带日志框架功能比较简单，仅提供print、panic、fatal三个方法，对于常规的日志切割等功能并未提供支持。
这里推荐使用sirupsen/logrus日志库。

logrus feature

• 结构化、可插拔的日志模块
• 完全兼容官方log库接口
• Field机制
• 可扩展的HOOK机制
• TEXT与JSON两种可选格式

简单使用示例

std Logger

与官方log类似，logrus也提供了一个名为std的标准logger，对外导出的各类方法直接使用std记录日志，一般可按如下方式使用

package main

import log "github.com/sirupsen/logrus"

func main() {

    log.Info("hello, world.")
}

自建Logger实例

package main

import (
  "os"
  "github.com/sirupsen/logrus"
)

// Create a new instance of the logger. You can have any number of instances.
var log = logrus.New()

func main() {
  // The API for setting attributes is a little different than the package level
  // exported logger. See Godoc.
  log.Out = os.Stdout

  // You could set this to any `io.Writer` such as a file
  // file, err := os.OpenFile("logrus.log", os.O_CREATE|os.O_WRONLY, 0666)
  // if err == nil {
  //  log.Out = file
  // } else {
  //  log.Info("Failed to log to file, using default stderr")
  // }

  log.WithFields(logrus.Fields{
    "animal": "walrus",
    "size":   10,
  }).Info("A group of walrus emerges from the ocean")
}

输出到本地文件系统

下面示例代码，通过一个hook将日志输出到本地文件系统中，并提供日志切割功能

import (
    "github.com/lestrrat/go-file-rotatelogs"
    "github.com/rifflock/lfshook"
    log "github.com/sirupsen/logrus"
    "time"
    "os"
    "github.com/pkg/errors"
    "path"
)
// config logrus log to local filesystem, with file rotation
func ConfigLocalFilesystemLogger(logPath string, logFileName string, maxAge time.Duration, rotationTime time.Duration) {
    baseLogPaht := path.Join(logPath, logFileName)
    writer, err := rotatelogs.New(
        baseLogPaht+".%Y%m%d%H%M",
        rotatelogs.WithLinkName(baseLogPaht), // 生成软链，指向最新日志文件
        rotatelogs.WithMaxAge(maxAge), // 文件最大保存时间
        rotatelogs.WithRotationTime(rotationTime), // 日志切割时间间隔
    )
    if err != nil {
        log.Errorf("config local file system logger error. %+v", errors.WithStack(err))
    }
    lfHook := lfshook.NewHook(lfshook.WriterMap{
        log.DebugLevel: writer, // 为不同级别设置不同的输出目的
        log.InfoLevel:  writer,
        log.WarnLevel:  writer,
        log.ErrorLevel: writer,
        log.FatalLevel: writer,
        log.PanicLevel: writer,
    })
    log.AddHook(lfHook)
}

输出到MQ或ES

如下示例代码通过hook将日志输出到amqp消息队列，或者es中。

import (
    "github.com/vladoatanasov/logrus_amqp"
    "gopkg.in/olivere/elastic.v5"
    "gopkg.in/sohlich/elogrus.v2"
    log "github.com/sirupsen/logrus"
    "github.com/pkg/errors"
)

// config logrus log to amqp
func ConfigAmqpLogger(server, username, password, exchange, exchangeType, virtualHost, routingKey string) {
    hook := logrus_amqp.NewAMQPHookWithType(server, username, password, exchange, exchangeType, virtualHost, routingKey)
    log.AddHook(hook)
}

// config logrus log to es
func ConfigESLogger(esUrl string, esHOst string, index string) {
    client, err := elastic.NewClient(elastic.SetURL(esUrl))
    if err != nil {
        log.Errorf("config es logger error. %+v", errors.WithStack(err))
    }
    esHook, err := elogrus.NewElasticHook(client, esHOst, log.DebugLevel, index)
    if err != nil {
        log.Errorf("config es logger error. %+v", errors.WithStack(err))
    }
    log.AddHook(esHook)
}

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