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<?php |
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namespace RemiSan\Lock\Locker; |
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use Psr\Log\LoggerAwareInterface; |
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use Psr\Log\LoggerAwareTrait; |
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use Psr\Log\NullLogger; |
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use RemiSan\Lock\Exceptions\LockingException; |
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use RemiSan\Lock\Exceptions\UnlockingException; |
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use RemiSan\Lock\Lock; |
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use RemiSan\Lock\Locker; |
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use RemiSan\Lock\LockStore; |
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use RemiSan\Lock\TokenGenerator; |
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use Symfony\Component\Stopwatch\Stopwatch; |
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final class SingleStoreLocker implements Locker, LoggerAwareInterface |
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{ |
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use LoggerAwareTrait; |
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/** @var LockStore */ |
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private $store; |
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/** @var TokenGenerator */ |
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private $tokenGenerator; |
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/** @var Stopwatch */ |
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private $stopwatch; |
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/** |
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* SingleStoreLocker constructor. |
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* |
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* @param LockStore $store The persisting store for the locks |
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* @param TokenGenerator $tokenGenerator The token generator |
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* @param Stopwatch $stopwatch A way to measure time passed |
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*/ |
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public function __construct( |
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$store, |
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TokenGenerator $tokenGenerator, |
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Stopwatch $stopwatch |
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) { |
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$this->store = $store; |
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$this->tokenGenerator = $tokenGenerator; |
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$this->stopwatch = $stopwatch; |
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$this->logger = new NullLogger(); |
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} |
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/** |
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* {@inheritdoc} |
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*/ |
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public function lock($resource, $ttl = null, $retryDelay = 0, $retryCount = 0) |
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{ |
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$lock = new Lock((string) $resource, $this->tokenGenerator->generateToken()); |
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$tried = 0; |
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while (true) { |
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try { |
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return $this->lockAndCheckQuorumAndTtl($lock, $ttl); |
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} catch (LockingException $e) { |
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$this->logger->notice($e->getMessage(), ['resource' => $lock->getResource()]); |
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} |
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if ($tried++ === $retryCount) { |
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break; |
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} |
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$this->waitBeforeRetrying($retryDelay); |
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} |
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throw new LockingException('Failed locking the resource.'); |
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} |
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/** |
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* {@inheritdoc} |
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*/ |
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public function isLocked($resource) |
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{ |
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return $this->store->exists((string) $resource); |
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} |
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/** |
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* {@inheritdoc} |
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*/ |
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public function unlock(Lock $lock) |
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{ |
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if (!$this->store->delete($lock)) { |
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if ($this->store->exists($lock->getResource())) { |
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// Only throw an exception if the lock is still present |
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throw new UnlockingException('Failed releasing the lock.'); |
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} |
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} |
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} |
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/** |
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* Try locking resource on store. |
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* |
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* Measure the time to do it and reject if time to lock on store have exceeded the ttl. |
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* |
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* @param Lock $lock The lock instance |
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* @param int $ttl Time to live in milliseconds |
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* |
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* @throws LockingException |
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* |
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* @return Lock |
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*/ |
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private function lockAndCheckQuorumAndTtl(Lock $lock, $ttl) |
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{ |
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$timeMeasure = $this->stopwatch->start($lock->getToken()); |
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$this->store->set($lock, $ttl); |
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$timeMeasure->stop(); |
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if ($ttl) { |
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$this->checkTtl($timeMeasure->getDuration(), $ttl); |
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$lock->setValidityEndTime($timeMeasure->getOrigin() + $ttl); |
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} |
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return $lock; |
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} |
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/** |
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* Make the script wait before retrying to lock. |
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* |
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* @param int $retryDelay The retry delay in milliseconds |
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*/ |
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private function waitBeforeRetrying($retryDelay) |
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{ |
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usleep($retryDelay * 1000); |
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} |
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/** |
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* Checks if the elapsed time is inferior to the ttl. |
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* |
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* To the elapsed time is added a drift time to have a margin of error. |
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* If this adjusted time is greater than the ttl, it will throw a LockingException. |
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* |
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* @param int $elapsedTime The time elapsed in milliseconds |
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* @param int $ttl The time to live in milliseconds |
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* |
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* @throws LockingException |
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*/ |
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private function checkTtl($elapsedTime, $ttl) |
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{ |
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$adjustedElapsedTime = $elapsedTime + $this->store->getDrift($ttl); |
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if ($adjustedElapsedTime >= $ttl) { |
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throw new LockingException('Time to lock the resource has exceeded the ttl.'); |
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} |
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} |
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} |
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remi-san /
lock
