004d58fdb8
If a cache entry is dependent on the code that's running, upgrading (or enabling/disabling plugins) can generate hard-to-track inconsistencies. This change adds a close-to-unique fingerprint of the running code to some cache keys, so that if the fingerprint changes, the old values are ignored and new values are used. If the automated uniqueness fails, an administrator can add an extra config value, $config['site']['build'], that's thrown into the key also.
271 lines
7.6 KiB
PHP
271 lines
7.6 KiB
PHP
<?php
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/**
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* StatusNet, the distributed open-source microblogging tool
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*
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* Cache interface plus default in-memory cache implementation
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*
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* PHP version 5
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*
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* LICENCE: This program 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 as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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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
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*
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* @category Cache
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* @package StatusNet
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* @author Evan Prodromou <evan@status.net>
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* @copyright 2009 StatusNet, Inc.
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* @license http://www.fsf.org/licensing/licenses/agpl-3.0.html GNU Affero General Public License version 3.0
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* @link http://status.net/
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*/
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/**
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* Interface for caching
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*
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* An abstract interface for caching. Because we originally used the
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* Memcache plugin directly, the interface uses a small subset of the
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* Memcache interface.
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*
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* @category Cache
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* @package StatusNet
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* @author Evan Prodromou <evan@status.net>
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* @copyright 2009 StatusNet, Inc.
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* @license http://www.fsf.org/licensing/licenses/agpl-3.0.html AGPL 3.0
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* @link http://status.net/
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*/
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class Cache
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{
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var $_items = array();
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static $_inst = null;
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const COMPRESSED = 1;
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/**
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* Singleton constructor
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*
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* Use this to get the singleton instance of Cache.
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*
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* @return Cache cache object
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*/
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static function instance()
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{
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if (is_null(self::$_inst)) {
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self::$_inst = new Cache();
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}
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return self::$_inst;
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}
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/**
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* Create a cache key from input text
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*
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* Builds a cache key from input text. Helps to namespace
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* the cache area (if shared with other applications or sites)
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* and prevent conflicts.
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*
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* @param string $extra the real part of the key
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*
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* @return string full key
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*/
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static function key($extra)
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{
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$base_key = common_config('cache', 'base');
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if (empty($base_key)) {
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$base_key = common_keyize(common_config('site', 'name'));
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}
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return 'statusnet:' . $base_key . ':' . $extra;
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}
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/**
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* Create a cache key for data dependent on code
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*
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* For cache elements that are dependent on changes in code, this creates
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* a more-or-less fingerprint of the current running code and adds it to
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* the cache key. In the case of an upgrade of core, or addition or
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* removal of plugins, a new unique fingerprint is generated and used.
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*
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* There can still be problems with a) differences in versions of the
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* plugins and b) people running code between official versions. This is
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* usually a problem only for experienced users like developers, who know
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* how to clear their cache.
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*
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* For sites that run code between versions (like the status.net cloud),
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* there's an additional build number configuration setting.
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*
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* @param string $extra the real part of the key
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*
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* @return string full key
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*/
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static function codeKey($extra)
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{
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static $prefix = null;
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if (empty($prefix)) {
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$plugins = StatusNet::getActivePlugins();
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$names = array();
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foreach ($plugins as $plugin) {
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$names[] = $plugin[0];
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}
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$names = array_unique($names);
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asort($names);
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// Unique enough.
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$uniq = crc32(implode(',', $names));
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$build = common_config('site', 'build');
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$prefix = STATUSNET_VERSION.':'.$build.':'.$uniq;
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}
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return Cache::key($prefix.':'.$extra);
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}
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/**
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* Make a string suitable for use as a key
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*
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* Useful for turning primary keys of tables into cache keys.
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*
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* @param string $str string to turn into a key
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*
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* @return string keyized string
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*/
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static function keyize($str)
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{
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$str = strtolower($str);
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$str = preg_replace('/\s/', '_', $str);
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return $str;
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}
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/**
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* Get a value associated with a key
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*
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* The value should have been set previously.
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*
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* @param string $key Lookup key
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*
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* @return string retrieved value or null if unfound
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*/
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function get($key)
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{
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$value = false;
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if (Event::handle('StartCacheGet', array(&$key, &$value))) {
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if (array_key_exists($key, $this->_items)) {
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$value = unserialize($this->_items[$key]);
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}
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Event::handle('EndCacheGet', array($key, &$value));
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}
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return $value;
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}
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/**
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* Set the value associated with a key
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*
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* @param string $key The key to use for lookups
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* @param string $value The value to store
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* @param integer $flag Flags to use, may include Cache::COMPRESSED
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* @param integer $expiry Expiry value, mostly ignored
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*
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* @return boolean success flag
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*/
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function set($key, $value, $flag=null, $expiry=null)
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{
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$success = false;
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if (Event::handle('StartCacheSet', array(&$key, &$value, &$flag,
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&$expiry, &$success))) {
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$this->_items[$key] = serialize($value);
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$success = true;
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Event::handle('EndCacheSet', array($key, $value, $flag,
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$expiry));
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}
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return $success;
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}
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/**
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* Atomically increment an existing numeric value.
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* Existing expiration time should remain unchanged, if any.
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*
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* @param string $key The key to use for lookups
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* @param int $step Amount to increment (default 1)
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*
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* @return mixed incremented value, or false if not set.
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*/
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function increment($key, $step=1)
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{
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$value = false;
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if (Event::handle('StartCacheIncrement', array(&$key, &$step, &$value))) {
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// Fallback is not guaranteed to be atomic,
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// and may original expiry value.
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$value = $this->get($key);
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if ($value !== false) {
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$value += $step;
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$ok = $this->set($key, $value);
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$got = $this->get($key);
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}
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Event::handle('EndCacheIncrement', array($key, $step, $value));
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}
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return $value;
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}
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/**
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* Delete the value associated with a key
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*
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* @param string $key Key to delete
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*
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* @return boolean success flag
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*/
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function delete($key)
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{
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$success = false;
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if (Event::handle('StartCacheDelete', array(&$key, &$success))) {
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if (array_key_exists($key, $this->_items)) {
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unset($this->_items[$key]);
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}
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$success = true;
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Event::handle('EndCacheDelete', array($key));
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}
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return $success;
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}
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/**
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* Close or reconnect any remote connections, such as to give
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* daemon processes a chance to reconnect on a fresh socket.
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*
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* @return boolean success flag
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*/
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function reconnect()
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{
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$success = false;
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if (Event::handle('StartCacheReconnect', array(&$success))) {
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$success = true;
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Event::handle('EndCacheReconnect', array());
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}
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return $success;
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}
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}
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