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[mediawiki.git] / includes / objectcache / MultiWriteBagOStuff.php

<?php
/**
 * Wrapper for object caching in different caches.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 * http://www.gnu.org/copyleft/gpl.html
 *
 * @file
 * @ingroup Cache
 */

/**
 * A cache class that replicates all writes to multiple child caches. Reads
 * are implemented by reading from the caches in the order they are given in
 * the configuration until a cache gives a positive result.
 *
 * @ingroup Cache
 */
class MultiWriteBagOStuff extends BagOStuff {
        /** @var array BagOStuff[] */
        protected $caches;

        /**
         * Constructor. Parameters are:
         *
         *   - caches:   This should have a numbered array of cache parameter
         *               structures, in the style required by $wgObjectCaches. See
         *               the documentation of $wgObjectCaches for more detail.
         *
         * @param array $params
         * @throws MWException
         */
        public function __construct( $params ) {
                if ( !isset( $params['caches'] ) ) {
                        throw new MWException( __METHOD__ . ': the caches parameter is required' );
                }

                $this->caches = array();
                foreach ( $params['caches'] as $cacheInfo ) {
                        $this->caches[] = ObjectCache::newFromParams( $cacheInfo );
                }
        }

        /**
         * @param bool $debug
         */
        public function setDebug( $debug ) {
                $this->doWrite( 'setDebug', $debug );
        }

        /**
         * @param string $key
         * @param mixed $casToken [optional]
         * @return bool|mixed
         */
        public function get( $key, &$casToken = null ) {
                foreach ( $this->caches as $cache ) {
                        $value = $cache->get( $key );
                        if ( $value !== false ) {
                                return $value;
                        }
                }
                return false;
        }

        /**
         * @param mixed $casToken
         * @param string $key
         * @param mixed $value
         * @param mixed $exptime
         * @return bool
         */
        public function cas( $casToken, $key, $value, $exptime = 0 ) {
                throw new MWException( "CAS is not implemented in " . __CLASS__ );
        }

        /**
         * @param string $key
         * @param mixed $value
         * @param int $exptime
         * @return bool
         */
        public function set( $key, $value, $exptime = 0 ) {
                return $this->doWrite( 'set', $key, $value, $exptime );
        }

        /**
         * @param string $key
         * @param int $time
         * @return bool
         */
        public function delete( $key, $time = 0 ) {
                return $this->doWrite( 'delete', $key, $time );
        }

        /**
         * @param string $key
         * @param mixed $value
         * @param int $exptime
         * @return bool
         */
        public function add( $key, $value, $exptime = 0 ) {
                return $this->doWrite( 'add', $key, $value, $exptime );
        }

        /**
         * @param string $key
         * @param int $value
         * @return bool|null
         */
        public function incr( $key, $value = 1 ) {
                return $this->doWrite( 'incr', $key, $value );
        }

        /**
         * @param string $key
         * @param int $value
         * @return bool
         */
        public function decr( $key, $value = 1 ) {
                return $this->doWrite( 'decr', $key, $value );
        }

        /**
         * @param string $key
         * @param int $timeout
         * @return bool
         */
        public function lock( $key, $timeout = 0 ) {
                // Lock only the first cache, to avoid deadlocks
                if ( isset( $this->caches[0] ) ) {
                        return $this->caches[0]->lock( $key, $timeout );
                } else {
                        return true;
                }
        }

        /**
         * @param string $key
         * @return bool
         */
        public function unlock( $key ) {
                if ( isset( $this->caches[0] ) ) {
                        return $this->caches[0]->unlock( $key );
                } else {
                        return true;
                }
        }

        /**
         * @param string $key
         * @param Closure $callback Callback method to be executed
         * @param int $exptime Either an interval in seconds or a unix timestamp for expiry
         * @param int $attempts The amount of times to attempt a merge in case of failure
         * @return bool Success
         */
        public function merge( $key, Closure $callback, $exptime = 0, $attempts = 10 ) {
                return $this->doWrite( 'merge', $key, $callback, $exptime );
        }

        public function getLastError() {
                return isset( $this->caches[0] ) ? $this->caches[0]->getLastError() : self::ERR_NONE;
        }

        public function clearLastError() {
                if ( isset( $this->caches[0] ) ) {
                        $this->caches[0]->clearLastError();
                }
        }

        /**
         * @param string $method
         * @return bool
         */
        protected function doWrite( $method /*, ... */ ) {
                $ret = true;
                $args = func_get_args();
                array_shift( $args );

                foreach ( $this->caches as $cache ) {
                        if ( !call_user_func_array( array( $cache, $method ), $args ) ) {
                                $ret = false;
                        }
                }
                return $ret;
        }

        /**
         * Delete objects expiring before a certain date.
         *
         * Succeed if any of the child caches succeed.
         * @param string $date
         * @param bool|callable $progressCallback
         * @return bool
         */
        public function deleteObjectsExpiringBefore( $date, $progressCallback = false ) {
                $ret = false;
                foreach ( $this->caches as $cache ) {
                        if ( $cache->deleteObjectsExpiringBefore( $date, $progressCallback ) ) {
                                $ret = true;
                        }
                }
                return $ret;
        }
}