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<?php |
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declare(strict_types=1); |
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namespace Yiisoft\Mutex\File; |
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use Yiisoft\Files\FileHelper; |
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use Yiisoft\Mutex\Mutex; |
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use function chmod; |
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use function clearstatcache; |
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use function fclose; |
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use function fileinode; |
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use function flock; |
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use function fopen; |
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use function fstat; |
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use function md5; |
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use function unlink; |
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/** |
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* FileMutex implements mutex "lock" mechanism via local file system files. |
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* |
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* This component relies on PHP {@see flock()} function. |
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* |
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* > Note: this component can maintain the locks only for the single web server, |
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* > it probably will not suffice in case you are using cloud server solution. |
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* |
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* > Warning: due to {@see flock()} function nature this component is unreliable when |
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* > using a multithreaded server API like ISAPI. |
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*/ |
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final class FileMutex extends Mutex |
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{ |
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private string $lockFilePath; |
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private ?int $fileMode; |
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/** |
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* @var closed-resource|resource|null Stores opened lock file resource. |
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*/ |
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private $lockResource = null; |
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/** |
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* @param string $name Mutex name. |
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* @param string $mutexPath The directory to store mutex files. |
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* @param int $directoryMode The permission to be set for newly created directories. |
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* This value will be used by PHP {@see chmod()} function. No umask will be applied. Defaults to 0775, |
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* meaning the directory is read-writable by owner and group, but read-only for other users. |
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* @param int|null $fileMode The permission to be set for newly created mutex files. |
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* This value will be used by PHP {@see chmod()} function. No umask will be applied. |
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*/ |
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public function __construct(string $name, string $mutexPath, int $directoryMode = 0775, int $fileMode = null) |
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{ |
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FileHelper::ensureDirectory($mutexPath, $directoryMode); |
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$this->lockFilePath = $mutexPath . DIRECTORY_SEPARATOR . md5($name) . '.lock'; |
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$this->fileMode = $fileMode; |
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parent::__construct(self::class, $name); |
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} |
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protected function acquireLock(int $timeout = 0): bool |
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{ |
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$resource = fopen($this->lockFilePath, 'wb+'); |
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if ($resource === false) { |
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return false; |
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} |
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if ($this->fileMode !== null) { |
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@chmod($this->lockFilePath, $this->fileMode); |
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} |
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if (!flock($resource, LOCK_EX | LOCK_NB)) { |
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fclose($resource); |
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return false; |
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} |
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// Under unix, we delete the lock file before releasing the related handle. Thus, it's possible that we've |
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// acquired a lock on a non-existing file here (race condition). We must compare the inode of the lock file |
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// handle with the inode of the actual lock file. |
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// If they do not match we simply continue the loop since we can assume the inodes will be equal on the |
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// next try. |
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// Example of race condition without inode-comparison: |
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// Script A: locks file |
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// Script B: opens file |
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// Script A: unlinks and unlocks file |
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// Script B: locks handle of *unlinked* file |
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// Script C: opens and locks *new* file |
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// In this case we would have acquired two locks for the same file path. |
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if (DIRECTORY_SEPARATOR !== '\\' && fstat($resource)['ino'] !== @fileinode($this->lockFilePath)) { |
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clearstatcache(true, $this->lockFilePath); |
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flock($resource, LOCK_UN); |
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fclose($resource); |
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return false; |
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} |
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$this->lockResource = $resource; |
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return true; |
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} |
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protected function releaseLock(): bool |
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{ |
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if (!is_resource($this->lockResource)) { |
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return false; |
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} |
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if (DIRECTORY_SEPARATOR === '\\') { |
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// Under windows, it's not possible to delete a file opened via fopen (either by own or other process). |
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// That's why we must first unlock and close the handle and then *try* to delete the lock file. |
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flock($this->lockResource, LOCK_UN); |
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fclose($this->lockResource); |
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@unlink($this->lockFilePath); |
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} else { |
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// Under unix, it's possible to delete a file opened via fopen (either by own or other process). |
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// That's why we must unlink (the currently locked) lock file first and then unlock and close the handle. |
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@unlink($this->lockFilePath); |
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flock($this->lockResource, LOCK_UN); |
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fclose($this->lockResource); |
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} |
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$this->lockResource = null; |
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return true; |
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} |
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} |
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yiisoft /
mutex-file
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