glog基本用法

package main

import (
    "flag"
    "github.com/golang/glog"
)

func main() {
    flag.Parse()

    defer glog.Flush()
    glog.Info("This is a Info log")
    glog.Warning("This is a Warning log")
    glog.Error("This is a Error log")

    glog.V(1).Infoln("level 1")
    glog.V(2).Infoln("level 2")
}

这里log产生后会暂存在内存的buffer，只有调用glog.Flush()才会写入文件，glog的package的init函数启动了一个flushDaemon的goroutine来定时Flush，时间为30s，在程序退出之前需要defer来方式这种问题的发生

直接通过指定日志路径的方式运行

go run main.go -log_dir="./"

会生成不同级别的日志文件

lrwxr-xr-x  1 mrwhy  staff   52  4 10 23:42 main.ERROR -> main.whydomain.mrwhy.log.ERROR.20210410-234226.86055
lrwxr-xr-x  1 mrwhy  staff   51  4 10 23:42 main.INFO -> main.whydomain.mrwhy.log.INFO.20210410-234226.86055
lrwxr-xr-x  1 mrwhy  staff   54  4 10 23:42 main.WARNING -> main.whydomain.mrwhy.log.WARNING.20210410-234226.86055
-rw-r--r--  1 mrwhy  staff  271  4 10 23:41 main.go
-rw-r--r--  1 mrwhy  staff  250  4 10 23:42 main.whydomain.mrwhy.log.ERROR.20210410-234226.86055
-rw-r--r--  1 mrwhy  staff  375  4 10 23:42 main.whydomain.mrwhy.log.INFO.20210410-234226.86055
-rw-r--r--  1 mrwhy  staff  314  4 10 23:42 main.whydomain.mrwhy.log.WARNING.20210410-234226.86055

Info日志内容

Log file created at: 2021/04/10 23:42:26
Running on machine: whydomain
Binary: Built with gc go1.13.15 for darwin/amd64
Log line format: [IWEF]mmdd hh:mm:ss.uuuuuu threadid file:line] msg
I0410 23:42:26.076030   86055 main.go:11] This is a Info log
W0410 23:42:26.076561   86055 main.go:12] This is a Warning log
E0410 23:42:26.076832   86055 main.go:13] This is a Error log

可以看到是没有level1和level2的输出的，需要在启动的时候通过-v来指定，小于这个级别的才会进行输出，默认为0

相当于

if glog.V(1) {
    Info()
}

执行

go run main.go -log_dir="./" -v=1

就看到只有level1的日志输出了

启动参数

  -alsologtostderr
        log to standard error as well as files
  -log_backtrace_at value
        when logging hits line file:N, emit a stack trace
  -log_dir string
        If non-empty, write log files in this directory
  -logtostderr
        log to standard error instead of files
  -stderrthreshold value
        logs at or above this threshold go to stderr
  -v value
        log level for V logs
  -vmodule value
        comma-separated list of pattern=N settings for file-filtered logging

常用的还有

• alsologtostderr：日志写入文件的同时，输出到stderr
• vmodule：可以为不同文件的日志打印配置不同的-v值
• log_backtrace_at：运行到指定位置打印堆栈信息

alsologtostderr

同级添加go文件

package main

import "github.com/golang/glog"

func bar() {
    glog.V(1).Info("level 1 in bar")
    glog.V(2).Info("level 2 in bar")
}

main.go引用bar方法

package main

import (
    "flag"
    "github.com/golang/glog"
)

func main() {
    flag.Parse()

    defer glog.Flush()
    glog.Info("This is a Info log")
    glog.Warning("This is a Warning log")
    glog.Error("This is a Error log")

    glog.V(1).Infoln("level 1")
    glog.V(2).Infoln("level 2")

    bar()
}

执行

go run ./ -log_dir="./" -v 1 -vmodule=bar=2

只有vmoudule大于v才生效

I0411 00:09:13.347980   88302 main.go:16] level 1
I0411 00:09:13.347995   88302 bar.go:6] level 1 in bar
I0411 00:09:13.348000   88302 bar.go:7] level 2 in bar