go监视文件改动

当修改/etc/kubernetes/下的配置时，配置会自动生效。其原理就是所有kubernetes服务会watch默认配置文件，当文件发生改动时，加载配置。

watch文件改动所使用的库是: github.com/fsnotify/fs…

code

监控/tmp/foo文件路径的改动，并打印出事件类型

package main

import (
	"log"

	"github.com/fsnotify/fsnotify"
)

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

	done := make(chan bool)
	go func() {
		for {
			select {
			case event, ok := <-watcher.Events:
				if !ok {
					return
				}
				log.Println("event:", event)
				if event.Op&fsnotify.Write == fsnotify.Write {
					log.Println("modified file:", event.Name)
				}
			case err, ok := <-watcher.Errors:
				if !ok {
					return
				}
				log.Println("error:", err)
			}
		}
	}()
        // watch file path /tmp/foo
	err = watcher.Add("/tmp/foo")
	if err != nil {
		log.Fatal(err)
	}
	<-done
}

test

改动/tmp/foo文件内容，观察输出:

2022/06/16 09:42:16 event: "/tmp/foo": WRITE
2022/06/16 09:42:16 modified file: /tmp/foo
2022/06/16 09:42:26 event: "/tmp/foo": REMOVE
^Csignal: interrupt