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<?php |
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declare(strict_types=1); |
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/** |
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* @copyright Copyright (c) 2016, ownCloud, Inc. |
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* |
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* @author Christoph Wurst <[email protected]> |
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* @author Robin Appelman <[email protected]> |
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* @author Roeland Jago Douma <[email protected]> |
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* |
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* @license AGPL-3.0 |
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* |
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* This code is free software: you can redistribute it and/or modify |
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* it under the terms of the GNU Affero General Public License, version 3, |
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* as published by the Free Software Foundation. |
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* |
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* This program is distributed in the hope that it will be useful, |
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* but WITHOUT ANY WARRANTY; without even the implied warranty of |
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
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* GNU Affero General Public License for more details. |
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* |
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* You should have received a copy of the GNU Affero General Public License, version 3, |
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* along with this program. If not, see <http://www.gnu.org/licenses/> |
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* |
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*/ |
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namespace OC\Lock; |
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use OCP\IMemcache; |
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use OCP\IMemcacheTTL; |
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use OCP\Lock\LockedException; |
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class MemcacheLockingProvider extends AbstractLockingProvider { |
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/** |
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* @var \OCP\IMemcache |
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*/ |
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private $memcache; |
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/** |
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* @param \OCP\IMemcache $memcache |
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* @param int $ttl |
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*/ |
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public function __construct(IMemcache $memcache, int $ttl = 3600) { |
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$this->memcache = $memcache; |
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$this->ttl = $ttl; |
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} |
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private function setTTL(string $path) { |
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if ($this->memcache instanceof IMemcacheTTL) { |
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$this->memcache->setTTL($path, $this->ttl); |
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} |
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} |
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/** |
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* @param string $path |
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* @param int $type self::LOCK_SHARED or self::LOCK_EXCLUSIVE |
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* @return bool |
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*/ |
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public function isLocked(string $path, int $type): bool { |
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$lockValue = $this->memcache->get($path); |
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if ($type === self::LOCK_SHARED) { |
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return $lockValue > 0; |
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} elseif ($type === self::LOCK_EXCLUSIVE) { |
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return $lockValue === 'exclusive'; |
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} else { |
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return false; |
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} |
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} |
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/** |
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* @param string $path |
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* @param int $type self::LOCK_SHARED or self::LOCK_EXCLUSIVE |
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* @param string $readablePath human readable path to use in error messages |
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* @throws \OCP\Lock\LockedException |
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*/ |
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public function acquireLock(string $path, int $type, string $readablePath = null) { |
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if ($type === self::LOCK_SHARED) { |
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if (!$this->memcache->inc($path)) { |
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throw new LockedException($path, null, $this->getExistingLockForException($path), $readablePath); |
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} |
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} else { |
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$this->memcache->add($path, 0); |
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if (!$this->memcache->cas($path, 0, 'exclusive')) { |
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throw new LockedException($path, null, $this->getExistingLockForException($path), $readablePath); |
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} |
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} |
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$this->setTTL($path); |
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$this->markAcquire($path, $type); |
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} |
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/** |
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* @param string $path |
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* @param int $type self::LOCK_SHARED or self::LOCK_EXCLUSIVE |
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*/ |
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public function releaseLock(string $path, int $type) { |
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if ($type === self::LOCK_SHARED) { |
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$ownSharedLockCount = $this->getOwnSharedLockCount($path); |
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$newValue = 0; |
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if ($ownSharedLockCount === 0) { // if we are not holding the lock, don't try to release it |
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return; |
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} |
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if ($ownSharedLockCount === 1) { |
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$removed = $this->memcache->cad($path, 1); // if we're the only one having a shared lock we can remove it in one go |
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if (!$removed) { //someone else also has a shared lock, decrease only |
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$newValue = $this->memcache->dec($path); |
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} |
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} else { |
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// if we own more than one lock ourselves just decrease |
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$newValue = $this->memcache->dec($path); |
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} |
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// if we somehow release more locks then exists, reset the lock |
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if ($newValue < 0) { |
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$this->memcache->cad($path, $newValue); |
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} |
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} elseif ($type === self::LOCK_EXCLUSIVE) { |
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$this->memcache->cad($path, 'exclusive'); |
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} |
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$this->markRelease($path, $type); |
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} |
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/** |
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* Change the type of an existing lock |
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* |
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* @param string $path |
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* @param int $targetType self::LOCK_SHARED or self::LOCK_EXCLUSIVE |
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* @throws \OCP\Lock\LockedException |
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*/ |
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public function changeLock(string $path, int $targetType) { |
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if ($targetType === self::LOCK_SHARED) { |
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if (!$this->memcache->cas($path, 'exclusive', 1)) { |
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throw new LockedException($path, null, $this->getExistingLockForException($path)); |
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} |
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} elseif ($targetType === self::LOCK_EXCLUSIVE) { |
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// we can only change a shared lock to an exclusive if there's only a single owner of the shared lock |
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if (!$this->memcache->cas($path, 1, 'exclusive')) { |
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throw new LockedException($path, null, $this->getExistingLockForException($path)); |
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} |
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} |
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$this->setTTL($path); |
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$this->markChange($path, $targetType); |
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} |
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private function getExistingLockForException($path) { |
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$existing = $this->memcache->get($path); |
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if (!$existing) { |
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return 'none'; |
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} elseif ($existing === 'exclusive') { |
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return $existing; |
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} else { |
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return $existing . ' shared locks'; |
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} |
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} |
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} |
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nextcloud /
server
