package main

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

func main() {
 log.WithFields(log.Fields{
  "animal": "walrus",
 }).Info("A walrus appears")
}

time="2018-08-11T15:42:22+08:00" level=info msg="A walrus appears" animal=walrus

package main

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

func init() {
  // 设置日志格式为json格式
  log.SetFormatter(&log.JSONFormatter{})

  // 设置将日志输出到标准输出（默认的输出为stderr，标准错误）
  // 日志消息输出可以是任意的io.writer类型
  log.SetOutput(os.Stdout)

  // 设置日志级别为warn以上
  log.SetLevel(log.WarnLevel)
}

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

  log.WithFields(log.Fields{
    "omg":  true,
    "number": 122,
  }).Warn("The group's number increased tremendously!")

  log.WithFields(log.Fields{
    "omg":  true,
    "number": 100,
  }).Fatal("The ice breaks!")
}

package main

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

// logrus提供了New()函数来创建一个logrus的实例。
// 项目中，可以创建任意数量的logrus实例。
var log = logrus.New()

func main() {
  // 为当前logrus实例设置消息的输出，同样地，
  // 可以设置logrus实例的输出到任意io.writer
  log.Out = os.Stdout

  // 为当前logrus实例设置消息输出格式为json格式。
  // 同样地，也可以单独为某个logrus实例设置日志级别和hook，这里不详细叙述。
  log.Formatter = &logrus.JSONFormatter{}

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

log.Fatalf("Failed to send event %s to topic %s with key %d", event, topic, key)
````

在logrus中不太提倡，logrus鼓励使用以下方式替代之：





<div class="se-preview-section-delimiter"></div>

```go
log.WithFields(log.Fields{
 "event": event,
 "topic": topic,
 "key": key,
}).Fatal("Failed to send event")

requestLogger := log.WithFields(log.Fields{"request_id": request_id, "user_ip": user_ip})
requestLogger.Info("something happened on that request") # will log request_id and user_ip
requestLogger.Warn("something not great happened")

// logrus在记录Levels()返回的日志级别的消息时会触发HOOK，
// 按照Fire方法定义的内容修改logrus.Entry。
type Hook interface {
  Levels() []Level
  Fire(*Entry) error
}

type DefaultFieldHook struct {
}

func (hook *DefaultFieldHook) Fire(entry *log.Entry) error {
  entry.Data["appName"] = "MyAppName"
  return nil
}

func (hook *DefaultFieldHook) Levels() []log.Level {
  return log.AllLevels
}

import (
  "github.com/lestrrat-go/file-rotatelogs"
  "github.com/rifflock/lfshook"
  log "github.com/sirupsen/logrus"
  "time"
)

func newLfsHook(logLevel *string, maxRemainCnt uint) log.Hook {
  writer, err := rotatelogs.New(
    logName+".%Y%m%d%H",
    // WithLinkName为最新的日志建立软连接，以方便随着找到当前日志文件
    rotatelogs.WithLinkName(logName),

    // WithRotationTime设置日志分割的时间，这里设置为一小时分割一次
    rotatelogs.WithRotationTime(time.Hour),

    // WithMaxAge和WithRotationCount二者只能设置一个，
    // WithMaxAge设置文件清理前的最长保存时间，
    // WithRotationCount设置文件清理前最多保存的个数。
    //rotatelogs.WithMaxAge(time.Hour*24),
    rotatelogs.WithRotationCount(maxRemainCnt),
  )

  if err != nil {
    log.Errorf("config local file system for logger error: %v", err)
  }

  level, ok := logLevels[*logLevel]

  if ok {
    log.SetLevel(level)
  } else {
    log.SetLevel(log.WarnLevel)
  }

  lfsHook := lfshook.NewHook(lfshook.WriterMap{
    log.DebugLevel: writer,
    log.InfoLevel: writer,
    log.WarnLevel: writer,
    log.ErrorLevel: writer,
    log.FatalLevel: writer,
    log.PanicLevel: writer,
  }, &log.TextFormatter{DisableColors: true})

  return lfsHook
}

client, err := elastic.NewClient(elastic.SetURL("http://localhost:9200"))
  if err != nil {
    log.Panic(err)
  }

// Index a tweet (using JSON serialization)
tweet1 := Tweet{User: "olivere", Message: "Take Five", Retweets: 0}
put1, err := client.Index().
  Index("twitter").
  Type("tweet").
  Id("1").
  BodyJson(tweet1).
  Do(context.Background())

msg := struct {
  Host   string
  Timestamp string `json:"@timestamp"`
  Message  string
  Data   logrus.Fields
  Level   string
}

import (
  "github.com/olivere/elastic"
  "gopkg.in/sohlich/elogrus"
)

func initLog() {
  client, err := elastic.NewClient(elastic.SetURL("http://localhost:9200"))
  if err != nil {
    log.Panic(err)
  }
  hook, err := elogrus.NewElasticHook(client, "localhost", log.DebugLevel, "mylog")
  if err != nil {
    log.Panic(err)
  }
  log.AddHook(hook)
}

GET http://localhost:9200/mylog/_search

HTTP/1.1 200 OK
content-type: application/json; charset=UTF-8
transfer-encoding: chunked

{
 "took": 1,
 "timed_out": false,
 "_shards": {
  "total": 5,
  "successful": 5,
  "failed": 0
 },
 "hits": {
  "total": 2474,
  "max_score": 1.0,
  "hits": [
   {
    "_index": "mylog",
    "_type": "log",
    "_id": "AWUw13jWnMZReb-jHQup",
    "_score": 1.0,
    "_source": {
     "Host": "localhost",
     "@timestamp": "2018-08-13T01:12:32.212818666Z",
     "Message": "!!!msb info not found",
     "Data": {},
     "Level": "ERROR"
    }
   },
   {
    "_index": "mylog",
    "_type": "log",
    "_id": "AWUw13jgnMZReb-jHQuq",
    "_score": 1.0,
    "_source": {
     "Host": "localhost",
     "@timestamp": "2018-08-13T01:12:32.223103348Z",
     "Message": "get postgres instances info failed, scrape metrics failed, error:msb env not found",
     "Data": {
      "source": "collector/exporter.go:71:Scrape()"
     },
     "Level": "ERROR"
    }
   },
   //...
   {
    "_index": "mylog",
    "_type": "log",
    "_id": "AWUw2f1enMZReb-jHQu_",
    "_score": 1.0,
    "_source": {
     "Host": "localhost",
     "@timestamp": "2018-08-13T01:15:17.212546892Z",
     "Message": "!!!msb info not found",
     "Data": {
      "source": "collector/exporter.go:71:Scrape()"
     },
     "Level": "ERROR"
    }
   },
   {
    "_index": "mylog",
    "_type": "log",
    "_id": "AWUw2NhmnMZReb-jHQu1",
    "_score": 1.0,
    "_source": {
     "Host": "localhost",
     "@timestamp": "2018-08-13T01:14:02.21276903Z",
     "Message": "!!!msb info not found",
     "Data": {},
     "Level": "ERROR"
    }
   }
  ]
 }
}