Go 用文件实现一个跨进程的 Mutex

[binderclip]

需求：

1. 进程内部可以实现 Mutex
2. 跨进程也可以实现 Mutex

可参考的：

• lockedfile package - cmd/go/internal/lockedfile - pkg.go.dev
  • 是一个内部 pkg，目前也没还开放 proposal: make the internal lockedfile package public · Issue #33974 · golang/go
  • 可以先用这个 lockedfile package - github.com/rogpeppe/go-internal/lockedfile - pkg.go.dev
• alexflint/go-filemutex: Like sync.Mutex, but works across processes

package lockedfile_sp

import (
	"fmt"
	"sync"
	"testing"
	"time"

	"github.com/rogpeppe/go-internal/lockedfile"
)

func TestLockedfileMutex(t *testing.T) {
	begin := time.Now()
	fmt.Println("start")
	mutex := lockedfile.MutexAt("/tmp/hello")

	wg := sync.WaitGroup{}

	wg.Add(2)
	go func() {
		defer wg.Done()
		unlock, err := mutex.Lock()
		if err != nil {
			panic(err)
		}
		defer unlock()

		fmt.Println("a", time.Since(begin))
		time.Sleep(time.Second * 3)
	}()

	go func() {
		defer wg.Done()
		unlock, err := mutex.Lock()
		if err != nil {
			panic(err)
		}
		defer unlock()

		fmt.Println("b", time.Since(begin))
		time.Sleep(time.Second * 3)
	}()

	wg.Wait()
	fmt.Println("end", time.Since(begin))
}

单进程执行：

start
a 267.708µs
b 3.001576625s
end 6.002901375s

多进程执行：

start
b 79.042µs
a 3.001326792s
end 6.002688917s

start
b 5.688241458s
a 8.689420375s
end 11.690721417s