tusd/memorylocker/memorylocker.go

73 lines
2.1 KiB
Go

// Package memorylocker provides an in-memory locking mechanism.
//
// When multiple processes are attempting to access an upload, whether it be
// by reading or writing, a synchronization mechanism is required to prevent
// data corruption, especially to ensure correct offset values and the proper
// order of chunks inside a single upload.
//
// MemoryLocker persists locks using memory and therefore allowing a simple and
// cheap mechanism. Locks will only exist as long as this object is kept in
// reference and will be erased if the program exits.
package memorylocker
import (
"sync"
"github.com/tus/tusd"
)
// MemoryLocker persists locks using memory and therefore allowing a simple and
// cheap mechanism. Locks will only exist as long as this object is kept in
// reference and will be erased if the program exits.
type MemoryLocker struct {
locks map[string]bool
mutex *sync.Mutex
}
// NewMemoryLocker creates a new in-memory locker. The DataStore parameter
// is only presented for back-wards compatibility and is ignored. Please
// use the New() function instead.
func NewMemoryLocker(_ tusd.DataStore) *MemoryLocker {
return New()
}
// New creates a new in-memory locker.
func New() *MemoryLocker {
return &MemoryLocker{
locks: make(map[string]bool),
mutex: new(sync.Mutex),
}
}
// UseIn adds this locker to the passed composer.
func (locker *MemoryLocker) UseIn(composer *tusd.StoreComposer) {
composer.UseLocker(locker)
}
// LockUpload tries to obtain the exclusive lock.
func (locker *MemoryLocker) LockUpload(id string) error {
locker.mutex.Lock()
defer locker.mutex.Unlock()
// Ensure file is not locked
if _, ok := locker.locks[id]; ok {
return tusd.ErrFileLocked
}
locker.locks[id] = true
return nil
}
// UnlockUpload releases a lock. If no such lock exists, no error will be returned.
func (locker *MemoryLocker) UnlockUpload(id string) error {
locker.mutex.Lock()
defer locker.mutex.Unlock()
// Deleting a non-existing key does not end in unexpected errors or panic
// since this operation results in a no-op
delete(locker.locks, id)
return nil
}