85 lines
2.2 KiB
Go
85 lines
2.2 KiB
Go
//go:build linux
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package processlock
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import (
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"errors"
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"fmt"
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"os"
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"path/filepath"
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"sync"
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"golang.org/x/sys/unix"
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)
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// Lock 持有与文件描述符绑定的 Linux advisory flock。
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// 锁文件可以永久存在；只有内核锁状态表示当前所有权。
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type Lock struct {
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mu sync.Mutex
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file *os.File
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}
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// Acquire 以非阻塞方式获取排他锁，并把当前 PID 写入文件用于诊断。
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func Acquire(path string) (*Lock, error) {
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if path == "" {
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return nil, errors.New("process lock path is required")
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}
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absPath, err := filepath.Abs(path)
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if err != nil {
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return nil, fmt.Errorf("resolve process lock path: %w", err)
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}
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if err := os.MkdirAll(filepath.Dir(absPath), 0o750); err != nil {
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return nil, fmt.Errorf("create process lock directory: %w", err)
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}
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file, err := os.OpenFile(absPath, os.O_CREATE|os.O_RDWR, 0o640)
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if err != nil {
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return nil, fmt.Errorf("open process lock: %w", err)
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}
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if err := unix.Flock(int(file.Fd()), unix.LOCK_EX|unix.LOCK_NB); err != nil {
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_ = file.Close()
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if errors.Is(err, unix.EWOULDBLOCK) || errors.Is(err, unix.EAGAIN) {
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return nil, ErrAlreadyLocked
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}
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return nil, fmt.Errorf("acquire process lock: %w", err)
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}
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if err := writeOwnerPID(file); err != nil {
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_ = unix.Flock(int(file.Fd()), unix.LOCK_UN)
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_ = file.Close()
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return nil, err
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}
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return &Lock{file: file}, nil
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}
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func writeOwnerPID(file *os.File) error {
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if err := file.Truncate(0); err != nil {
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return fmt.Errorf("truncate process lock metadata: %w", err)
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}
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if _, err := file.Seek(0, 0); err != nil {
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return fmt.Errorf("seek process lock metadata: %w", err)
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}
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if _, err := fmt.Fprintf(file, "%d\n", os.Getpid()); err != nil {
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return fmt.Errorf("write process lock metadata: %w", err)
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}
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if err := file.Sync(); err != nil {
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return fmt.Errorf("flush process lock metadata: %w", err)
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}
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return nil
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}
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// Close 释放内核锁并关闭文件描述符，不删除锁文件。
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func (l *Lock) Close() error {
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if l == nil {
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return nil
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}
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l.mu.Lock()
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defer l.mu.Unlock()
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if l.file == nil {
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return nil
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}
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file := l.file
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l.file = nil
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unlockErr := unix.Flock(int(file.Fd()), unix.LOCK_UN)
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closeErr := file.Close()
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return errors.Join(unlockErr, closeErr)
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}
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