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gitea/modules/globallock/locker.go

38 lines
1.6 KiB

// Copyright 2024 The Gitea Authors. All rights reserved.
// SPDX-License-Identifier: MIT
package globallock
import (
"context"
)
type Locker interface {
// Lock tries to acquire a lock for the given key, it blocks until the lock is acquired or the context is canceled.
//
// Lock returns a ReleaseFunc to release the lock, it cannot be nil.
// It's always safe to call this function even if it fails to acquire the lock, and it will do nothing in that case.
// And it's also safe to call it multiple times, but it will only release the lock once.
// That's why it's called ReleaseFunc, not UnlockFunc.
// But be aware that it's not safe to not call it at all; it could lead to a memory leak.
// So a recommended pattern is to use defer to call it:
// release, err := locker.Lock(ctx, "key")
// if err != nil {
// return err
// }
// defer release()
//
// Lock returns an error if failed to acquire the lock.
// Be aware that even the context is not canceled, it's still possible to fail to acquire the lock.
// For example, redis is down, or it reached the maximum number of tries.
Lock(ctx context.Context, key string) (ReleaseFunc, error)
// TryLock tries to acquire a lock for the given key, it returns immediately.
// It follows the same pattern as Lock, but it doesn't block.
// And if it fails to acquire the lock because it's already locked, not other reasons like redis is down,
// it will return false without any error.
TryLock(ctx context.Context, key string) (bool, ReleaseFunc, error)
}
// ReleaseFunc is a function that releases a lock.
type ReleaseFunc func()