How to re-create log file automatically in logrus/lumberjack on macOS

Question

I use logrus and lumberjack for log file on macOS.

logger := &lumberjack.Logger{
    // Log path
    Filename: filepath.Join(logFolder, "xxx.log"),
    // Log size MB
    MaxSize: 10,
    // Backup count
    MaxBackups: 3,
    // expire days
    // MaxAge: 28,
    // gzip compress
    Compress: false,
}
logrus.SetOutput(logger)

When I start my application, It will create log file as expected.
However, when my app is running, I manually delete log file, as my app is continuing to run, I expect it will re-create log file, however, the log file is not created.
But if I restart my app, the log file will be created again.
So what should I do to make my app (keep running) to re-create and write log file when log file is deleted.

Thanks in advance.

Answer 1

Here is another way to monitor the log file using fsnotify lib. fsnotify monitors the directory where xxx.log is located, tell lumberjack to Rotate() when xxx.log deleted.

import (
    "fmt"
    "log"
    "path/filepath"
    "time"

    "github.com/fsnotify/fsnotify"
    "gopkg.in/natefinch/lumberjack.v2"
)

func main() {
    logPath := "./xxx.log"
    logName := filepath.Base(logPath)

    logger := &lumberjack.Logger{
        // Log path
        Filename: logPath,
        // Log size MB
        MaxSize: 10,
        // Backup count
        MaxBackups: 3,
        // expire days
        // MaxAge: 28,
        // gzip compress
        Compress: false,
    }

    watcher, err := fsnotify.NewWatcher()
    if err != nil {
        log.Fatal(err)
    }
    defer watcher.Close()

    go func() {
        for event := range watcher.Events {
            if event.Op&fsnotify.Remove == fsnotify.Remove &&
                event.Name == logName {
                log.Println("rotate log", event.Name)
                logger.Rotate()
            }
        }
    }()

    err = watcher.Add(filepath.Dir(logPath))
    if err != nil {
        log.Fatal(err)
    }

    for {
        logger.Write([]byte(fmt.Sprintf("current time:%v\n", time.Now())))
        time.Sleep(3 * time.Second)
    }
}