它是一个结构化、插件化的日志记录库。完全兼容 golang 标准库中的日志模块。它还内置了 2 种日志输出格式 JSONFormatter 和 TextFormatter，来定义输出的日志格式。
github地址：https://github.com/sirupsen/logrus
logrus 使用使用的版本：logrus v1.8.1
1. 开始使用 package main import ( log "github.com/sirupsen/logrus" ) func main() { log.WithFields(log.Fields{ "animal": "walrus", }).Info("a walrus appears") }运行输出：
time="2021-11-11T17:41:48+08:00" level=info msg="a walrus appears" animal=walrus 2. 设置日志格式,日志级别,输出方式 设置日志格式1）内置日志格式
，logrus内置的formatter有 2 种，logrus.TextFormatter 和 logrus.JSONFormatter
logrus.JSONFormatter{}， 设置为 json 格式，所有设置选项在
log.SetFormatter(&log.JSONFormatter{ TimestampFormat: "2006-01-02 15:04:05", // 设置json里的日期输出格式 }) log.SetFormatter(&log.JSONFormatter{}) // 设置为json格式
logrus.TextFormatter{}，设置为文本格式，所有的设置选项在
log.SetFormatter(&log.TextFormatter{ TimestampFormat: "2006-01-02 15:04:05", ForceColors: true, EnvironmentOverrideColors: true, // FullTimestamp:true, // DisableLevelTruncation:true, })2）自定义日志格式
可以根据 接口自定义日志格式，里面有一个 Format 方法，这个 Format 方法里有一个struct类型数据 ， Entry.Data 是所有字段集合， 类型为 map[string]interface{}。
比如：entry.Data["msg"]，entry.Data["time"]`. The timestamp
package main import ( "fmt" jsoniter "github.com/json-iterator/go" log "github.com/sirupsen/logrus" ) type MyJSONFormatter struct { JSONPrefix string Otherdata string } func (my *MyJSONFormatter) Format(entry *log.Entry) ([]byte, error) { // fmt.Println(entry.Data["msg"]) entry.Data["msg"] = fmt.Sprintf("%s%s", my.JSONPrefix, my.Otherdata) json, err := jsoniter.Marshal(&entry.Data) if err != nil { return nil, fmt.Errorf("failed to marshal fields to JSON , %w", err) } return append(json, '\n'), nil } func main() { formatter := &MyJSONFormatter{ JSONPrefix: "jsonprefix-", Otherdata: ":otherdata:", } log.SetFormatter(formatter) log.Info("this is customered formatter") }3）第三方自定义formatter设置日志格式
FluentdFormatter. Formats entries that can be parsed by Kubernetes and Google Container Engine.
logstash. Logs fields as Logstash Events.
caption-json-formatter. logrus's message json formatter with human-readable caption added.
powerful-logrus-formatter. get fileName, log's line number and the latest function's name when print log; Sava log to files.
等等
设置日志级别logrus日志一共7级别, 从高到低: panic, fatal, error, warn, info, debug, trace.
log.SetLevel(log.WarnLevel) // 设置输出警告级别
设置日志输出方式log.SetOutput(os.Stdout) // 输入到 Stdout，默认输出到 Stderr
logfile, _ := os.OpenFile("./logrus.log", os.O_CREATE|os.O_RDWR|os.O_APPEND, 0644)
logrus.SetOutput(logfile) // 输出到文件里
例子：
package main import ( log "github.com/sirupsen/logrus" "os" ) func init() { log.SetFormatter(&log.JSONFormatter{}) // 设置 format json log.SetLevel(log.WarnLevel) // 设置输出警告级别 // Output to stdout instead of the default stderr log.SetOutput(os.Stdout) } func main() { log.WithFields(log.Fields{ "animal": "dog", "size": 10, }).Info("a group of dog emerges from the zoon") log.WithFields(log.Fields{ "omg": true, "number": 12, }).Warn("the group's number increased") log.WithFields(log.Fields{ "omg": true, "number": 100, }).Fatal("th ice breaks") // the logrus.Entry returned from WithFields() contextLogger := log.WithFields(log.Fields{ "common": "this is a common filed", "other": "i also should be logged always", }) // 共同字段输出 contextLogger.Info("I'll be logged with common and other field") contextLogger.Info("Me too") }运行输出：
{"level":"warning","msg":"the group's number increased","number":12,"omg":true,"time":"2021-11-11T18:00:55+08:00"} {"level":"fatal","msg":"th ice breaks","number":100,"omg":true,"time":"2021-11-11T18:00:55+08:00"}从输出的结果看出，Info 级别的日志信息都没有输出出来。
屏蔽设置日志级别的代码
func init() { log.SetFormatter(&log.JSONFormatter{}) // 设置 format json // log.SetLevel(log.WarnLevel) // 设置输出警告级别 }在运行输出：
{"animal":"dog","level":"info","msg":"a group of dog emerges from the zoon","size":10,"time":"2021-11-11T18:26:45+08:00"} {"level":"warning","msg":"the group's number increased","number":12,"omg":true,"time":"2021-11-11T18:26:45+08:00"} {"level":"fatal","msg":"th ice breaks","number":100,"omg":true,"time":"2021-11-11T18:26:45+08:00"} exit status 1从输出的日志信息来看，并没有输出 contextLogger 的日志info信息，日志信息没有输出，为啥没有输出日志？
把上面的 Fatal 输出日志屏蔽掉：
// log.WithFields(log.Fields{ // "omg": true, // "number": 100, // }).Fatal("th ice breaks")