78 lines
2 KiB
Go
78 lines
2 KiB
Go
// Package lock provides file-based locking for VM operations.
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package lock
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import (
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"fmt"
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"os"
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"path/filepath"
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"syscall"
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"time"
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"github.com/samber/mo"
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"qvm/internal/config"
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)
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// Lock represents an exclusive file lock on VM operations.
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type Lock struct {
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file *os.File
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}
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var lockPath = filepath.Join(config.StateDir, "vm.lock")
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// Acquire obtains an exclusive lock on VM operations.
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// Blocks until the lock is available or timeout is reached.
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func Acquire(timeout time.Duration) mo.Result[*Lock] {
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if err := os.MkdirAll(config.StateDir, 0755); err != nil {
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return mo.Err[*Lock](fmt.Errorf("failed to create state directory: %w", err))
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}
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file, err := os.OpenFile(lockPath, os.O_CREATE|os.O_RDWR, 0644)
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if err != nil {
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return mo.Err[*Lock](fmt.Errorf("failed to open lock file: %w", err))
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}
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deadline := time.Now().Add(timeout)
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for {
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err := syscall.Flock(int(file.Fd()), syscall.LOCK_EX|syscall.LOCK_NB)
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if err == nil {
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return mo.Ok(&Lock{file: file})
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}
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if time.Now().After(deadline) {
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file.Close()
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return mo.Err[*Lock](fmt.Errorf("timeout waiting for VM lock after %v", timeout))
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}
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time.Sleep(100 * time.Millisecond)
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}
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}
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// TryAcquire attempts to obtain an exclusive lock without blocking.
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// Returns error if lock is held by another process.
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func TryAcquire() mo.Result[*Lock] {
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if err := os.MkdirAll(config.StateDir, 0755); err != nil {
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return mo.Err[*Lock](fmt.Errorf("failed to create state directory: %w", err))
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}
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file, err := os.OpenFile(lockPath, os.O_CREATE|os.O_RDWR, 0644)
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if err != nil {
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return mo.Err[*Lock](fmt.Errorf("failed to open lock file: %w", err))
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}
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err = syscall.Flock(int(file.Fd()), syscall.LOCK_EX|syscall.LOCK_NB)
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if err != nil {
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file.Close()
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return mo.Err[*Lock](fmt.Errorf("VM operation in progress by another process"))
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}
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return mo.Ok(&Lock{file: file})
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}
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// Release releases the lock.
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func (l *Lock) Release() error {
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if l.file == nil {
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return nil
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}
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syscall.Flock(int(l.file.Fd()), syscall.LOCK_UN)
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return l.file.Close()
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}
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