Go的日志模块glog调研笔记

亦凉 2022-01-26 07:07 600阅读 0赞

**glog简介**  
glog是著名的google开源C++日志库glog([https://github.com/google/glog][https_github.com_google_glog])的golang版本，glog是一个轻量级的日志库，上手简单不需要配置文件并且稳定高效，可以自定义控制的内容比较少。   
glog主要有以下几个特点：   
1. glog有四种日志等级INFO < WARING < ERROR < FATAL，不同等级的日志是打印到不同文件的，低等级的日志文件中（INFO）会包含高等级的日志信息（ERROR）   
2. 通过命令行传递参数 –log\_dir指定日志文件的存放目录，目录如果不存在，需要事先创建，默认为os.TempDir() ，也就是默认目录是/tmp  
3. 可以根据文件大小切割日志文件，但是不能根据日期切割日志文件   
4. 日志输出格式是固定的(Lmmdd hh:mm:ss.uuuuuu threadid file:line\] msg…)不可以自定义   
5. 在程序开始时需要调用flag.Parse()解析命令行参数，在程序退出时需要调用glog.Flush() 确保将缓存区中的内容输出到文件中  
6. glog.V(1).Infoln("level 1")这行代码表示设置的-v参数大于V()里面的参数才执行后面的Infoln。如果不加-v参数，默认等级为0

**glob的参数**

// By default, all log statements write to files in a temporary directory.
    // This package provides several flags that modify this behavior.
    // As a result, flag.Parse must be called before any logging is done.
    //
    //  -logtostderr=false
    //      Logs are written to standard error instead of to files.
    //  -alsologtostderr=false
    //      Logs are written to standard error as well as to files.
    //  -stderrthreshold=ERROR
    //      Log events at or above this severity are logged to standard
    //      error as well as to files.
    //  -log_dir=""
    //      Log files will be written to this directory instead of the
    //      default temporary directory.
    //
    //  Other flags provide aids to debugging.
    //
    //  -log_backtrace_at=""
    //      When set to a file and line number holding a logging statement,
    //      such as
    //          -log_backtrace_at=gopherflakes.go:234
    //      a stack trace will be written to the Info log whenever execution
    //      hits that statement. (Unlike with -vmodule, the ".go" must be
    //      present.)
    //  -v=0
    //      Enable V-leveled logging at the specified level.
    //  -vmodule=""
    //      The syntax of the argument is a comma-separated list of pattern=N,
    //      where pattern is a literal file name (minus the ".go" suffix) or
    //      "glob" pattern and N is a V level. For instance,
    //          -vmodule=gopher*=3
    //      sets the V level to 3 in all Go files whose names begin "gopher".

**简单示例**  
下面是一个简单的例子, 假设该例子文件名为glob\_demo.go

//description: 演示Go的日志库glob的用法
    //note: 需要先安装该日志库，同时如果指定目录的话，需要先创建该目录,如果不指定目录，默认存放在/tmp下面
    //run: go get; go build glob_demo.go; ./glob_demo --log_dir="./"
    //date: 2019-05-28
    
    package main
    
    import (
    	"flag"
    	"github.com/golang/glog"
    )
    
    func main() {
    	//初始化命令行参数
    	flag.Parse()
    
    	//退出时调用，确保日志写入磁盘文件中
    	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.Info("info %d", 1)
    	glog.Warning("warning %d", 2)
    	glog.Error("error %d", 3)
    
    	//需要开启-v=xx参数之后才会打印出来
    	glog.V(1).Infoln("level 1")
    	glog.V(2).Infoln("level 2")
    }

首先安装glob日志库  
go get -v "github.com/golang/glob"  
然后编译运行  
go build glob\_demo.go  
./glob\_demo --log\_dir="./"  
./glob\_demo -v=3  
然后在当前目录或是tmp目录下面，可以看到各种日志文件，我们只需要查看符号链接文件即可，因为每次运行都会产生当前级别的日志文件，多次运行会有很多这种日志文件，而符号链接文件会始终指向最新的日志文件上

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**参考文献**

\[1\].[https://github.com/golang/glog][https_github.com_golang_glog]

[https_github.com_google_glog]: https://github.com/google/glog
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[https_github.com_golang_glog]: https://github.com/golang/glog