Merge pull request #16821 from owncloud/compare-and-delete-locking-watch

Compare and delete locking watch

lib/private/lock/memcachelockingprovider.php

@@ -91,9 +91,10 @@ class MemcacheLockingProvider implements ILockingProvider {
 			if (isset($this->acquiredLocks['shared'][$path]) and $this->acquiredLocks['shared'][$path] > 0) {
 				$this->memcache->dec($path);
 				$this->acquiredLocks['shared'][$path]--;
+				$this->memcache->cad($path, 0);
 			}
 		} else if ($type === self::LOCK_EXCLUSIVE) {
-			$this->memcache->cas($path, 'exclusive', 0);
+			$this->memcache->cad($path, 'exclusive');
 			unset($this->acquiredLocks['exclusive'][$path]);
 		}
 	}

lib/private/memcache/apc.php

@@ -31,6 +31,8 @@ class APC extends Cache implements IMemcache {
 		cas as casEmulated;
 	}
 
+	use CADTrait;
+
 	public function get($key) {
 		$result = apc_fetch($this->getPrefix() . $key, $success);
 		if (!$success) {

lib/private/memcache/arraycache.php

@@ -28,6 +28,8 @@ class ArrayCache extends Cache implements IMemcache {
 	/** @var array Array with the cached data */
 	protected $cachedData = array();
 
+	use CADTrait;
+
 	/**
 	 * {@inheritDoc}
 	 */

lib/private/memcache/cadtrait.php

@@ -0,0 +1,53 @@
+<?php
+/**
+ * @author Robin Appelman <icewind@owncloud.com>
+ *
+ * @copyright Copyright (c) 2015, ownCloud, Inc.
+ * @license AGPL-3.0
+ *
+ * This code is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License, version 3,
+ * as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License, version 3,
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>
+ *
+ */
+
+namespace OC\Memcache;
+
+trait CADTrait {
+	abstract public function get($key);
+
+	abstract public function remove($key);
+
+	abstract public function add($key, $value, $ttl = 0);
+
+	/**
+	 * Compare and delete
+	 *
+	 * @param string $key
+	 * @param mixed $old
+	 * @return bool
+	 */
+	public function cad($key, $old) {
+		//no native cas, emulate with locking
+		if ($this->add($key . '_lock', true)) {
+			if ($this->get($key) === $old) {
+				$this->remove($key);
+				$this->remove($key . '_lock');
+				return true;
+			} else {
+				$this->remove($key . '_lock');
+				return false;
+			}
+		} else {
+			return false;
+		}
+	}
+}

lib/private/memcache/memcached.php

@@ -34,6 +34,8 @@ class Memcached extends Cache implements IMemcache {
 	 */
 	private static $cache = null;
 
+	use CADTrait;
+
 	public function __construct($prefix = '') {
 		parent::__construct($prefix);
 		if (is_null(self::$cache)) {

lib/private/memcache/nullcache.php

@@ -55,6 +55,10 @@ class NullCache extends Cache implements \OCP\IMemcache {
 		return true;
 	}
 
+	public function cad($key, $old) {
+		return true;
+	}
+
 	public function clear($prefix = '') {
 		return true;
 	}

lib/private/memcache/redis.php

@@ -26,8 +26,6 @@ namespace OC\Memcache;
 use OCP\IMemcache;
 
 class Redis extends Cache implements IMemcache {
-	use CASTrait;
-
 	/**
 	 * @var \Redis $cache
 	 */
@@ -150,6 +148,48 @@ class Redis extends Cache implements IMemcache {
 		return self::$cache->decrBy($this->getNamespace() . $key, $step);
 	}
 
+	/**
+	 * Compare and set
+	 *
+	 * @param string $key
+	 * @param mixed $old
+	 * @param mixed $new
+	 * @return bool
+	 */
+	public function cas($key, $old, $new) {
+		if (!is_int($new)) {
+			$new = json_encode($new);
+		}
+		self::$cache->watch($this->getNamespace() . $key);
+		if ($this->get($key) === $old) {
+			$result = self::$cache->multi()
+				->set($this->getNamespace() . $key, $new)
+				->exec();
+			return ($result === false) ? false : true;
+		}
+		self::$cache->unwatch();
+		return false;
+	}
+
+	/**
+	 * Compare and delete
+	 *
+	 * @param string $key
+	 * @param mixed $old
+	 * @return bool
+	 */
+	public function cad($key, $old) {
+		self::$cache->watch($this->getNamespace() . $key);
+		if ($this->get($key) === $old) {
+			$result = self::$cache->multi()
+				->del($this->getNamespace() . $key)
+				->exec();
+			return ($result === false) ? false : true;
+		}
+		self::$cache->unwatch();
+		return false;
+	}
+
 	static public function isAvailable() {
 		return extension_loaded('redis')
 		&& version_compare(phpversion('redis'), '2.2.5', '>=');

lib/private/memcache/xcache.php

@@ -34,6 +34,8 @@ use OCP\IMemcache;
 class XCache extends Cache implements IMemcache {
 	use CASTrait;
 
+	use CADTrait;
+
 	/**
 	 * entries in XCache gets namespaced to prevent collisions between ownCloud instances and users
 	 */

lib/public/imemcache.php

@@ -76,4 +76,14 @@ interface IMemcache extends ICache {
 	 * @since 8.1.0
 	 */
 	public function cas($key, $old, $new);
+
+	/**
+	 * Compare and delete
+	 *
+	 * @param string $key
+	 * @param mixed $old
+	 * @return bool
+	 * @since 8.1.0
+	 */
+	public function cad($key, $old);
 }

tests/lib/memcache/cache.php

@@ -103,6 +103,18 @@ abstract class Cache extends \Test_Cache {
 		$this->assertEquals('bar1', $this->instance->get('foo'));
 	}
 
+	public function testCadNotChanged() {
+		$this->instance->set('foo', 'bar');
+		$this->assertTrue($this->instance->cad('foo', 'bar'));
+		$this->assertFalse($this->instance->hasKey('foo'));
+	}
+
+	public function testCadChanged() {
+		$this->instance->set('foo', 'bar1');
+		$this->assertFalse($this->instance->cad('foo', 'bar'));
+		$this->assertTrue($this->instance->hasKey('foo'));
+	}
+
 
 	protected function tearDown() {
 		if ($this->instance) {