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156 lines
4.7 KiB
156 lines
4.7 KiB
<?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 <christoph@winzerhof-wurst.at>
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* @author Jaakko Salo <jaakkos@gmail.com>
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* @author Robin Appelman <robin@icewind.nl>
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* @author Roeland Jago Douma <roeland@famdouma.nl>
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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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