Testing file notification latency

test-fsnotify.go

package main

import (
	"fmt"
	"io/ioutil"
	"log"
	"os"
	"time"

	"github.com/fsnotify/fsnotify"
)

func main() {
	timeChannel := make(chan time.Time, 1)

	go func() {
		currentTime := time.Now()
		err := ioutil.WriteFile("sample.txt", []byte(currentTime.String()), 0644)
		if err != nil {
			log.Fatalf("Failed to write to file: %v", err)
		}
		fmt.Printf("Written to file at: %v\n", currentTime.UnixNano())
		timeChannel <- currentTime
	}()

	go func() {
		watcher, err := fsnotify.NewWatcher()
		if err != nil {
			log.Fatalf("Failed to create file watcher: %v", err)
		}
		defer watcher.Close()

		err = watcher.Add("./sample.txt")
		if err != nil {
			log.Fatalf("Failed to add file to watcher: %v", err)
		}

		for {
			select {
			case event, ok := <-watcher.Events:
				if !ok {
					return
				}
				if event.Op&fsnotify.Write == fsnotify.Write {
					notificationTime := time.Now()
					writeTime := <-timeChannel
					timeDiff := notificationTime.Sub(writeTime)
					fmt.Printf("File change notification at: %v, time taken: %v ns\n", notificationTime.UnixNano(), timeDiff.Nanoseconds())
					os.Exit(0)
				}
			case err, ok := <-watcher.Errors:
				if !ok {
					return
				}
				fmt.Printf("Error watching file: %v\n", err)
			}
		}
	}()

	select {}
}