logging - 我应该在 Go 中关闭日志文件吗？

Question

我在 utils 包的 init() 方法中创建了一个全局 Logger。

```

 package utils

 var Logger *log.Logger

 func init() {

  logFile, _ := config.Configure.String("log_file")
  if len(logFile) == 0 {
     appRoot, _ := os.Getwd()
     logFile = filepath.Join(appRoot, "app_runtime.log")
  }

  f, err := os.OpenFile(logFile, os.O_WRONLY|os.O_CREATE|os.O_APPEND, 0666)
  //Look HERE!!! 

  if err != nil {
     panic(err)
  }
  Logger = log.New()

  //Log as JSON
  Logger.Formatter = &log.JSONFormatter{}

  //Output to stdout
  //When production, use file
  Logger.Out = f

  // Only log the debug severity or above.
  Logger.Level = log.DebugLevel
}

```

所以，我可以这样使用它:

utils.Logger.Info("这是调试信息")

我的问题是:我应该关闭日志文件吗？怎么办？

Answer 1

默认情况下，os.File将在应用程序退出时由垃圾收集器 (GC) 完成。来自 SetFinalizer文档

The finalizer for obj is scheduled to run at some arbitrary time after obj becomes unreachable. There is no guarantee that finalizers will run before a program exits, so typically they are useful only for releasing non-memory resources associated with an object during a long-running program. For example, an os.File object could use a finalizer to close the associated operating system file descriptor when a program discards an os.File without calling Close, but it would be a mistake to depend on a finalizer to flush an in-memory I/O buffer such as a bufio.Writer, because the buffer would not be flushed at program exit.

如果不想依赖GC，可以在main函数中手动关闭，如下:

func main() {
    //Close log writer when exit
    defer func(){
        if file, ok := Logger.Out.(*os.File); ok {
            file.Sync()
            file.Close()
        } else if handler, ok := Logger.Out.(io.Closer); ok {
            handler.Close()
        }
    }()

    //Your original codes
    //...
}

在上面的代码中，我们使用defer 语句来确保handler 在应用程序退出时关闭。由于 Logger.Out 可能被定义为 io.Writer，我们需要测试 Logger.Out 是否也实现了 io.Closer ，如果是，则关闭。如果 Logger.Out 是一个 os.File，我们还调用 Sync() 以确保所有内容都写入磁盘。

编辑
引用文档并添加 file.Sync() 以确保将文件内容写入磁盘。