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[mediawiki.git] / includes / BagOStuff.php

<?php
#
# Copyright (C) 2003-2004 Brion Vibber <brion@pobox.com>
# http://www.mediawiki.org/
#
# 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

/**
 * @defgroup Cache Cache
 *
 * @file
 * @ingroup Cache
 */

/**
 * interface is intended to be more or less compatible with
 * the PHP memcached client.
 *
 * backends for local hash array and SQL table included:
 * <code>
 *   $bag = new HashBagOStuff();
 *   $bag = new MediaWikiBagOStuff($tablename); # connect to db first
 * </code>
 *
 * @ingroup Cache
 */
abstract class BagOStuff {
        var $debugMode = false;

        public function set_debug( $bool ) {
                $this->debugMode = $bool;
        }

        /* *** THE GUTS OF THE OPERATION *** */
        /* Override these with functional things in subclasses */

        /**
         * Get an item with the given key. Returns false if it does not exist.
         * @param $key string
         */
        abstract public function get( $key );

        /**
         * Set an item. 
         * @param $key string
         * @param $value mixed
         * @param $exptime int Either an interval in seconds or a unix timestamp for expiry
         */
        abstract public function set( $key, $value, $exptime = 0 );

        /*
         * Delete an item.
         * @param $key string
         * @param $time int Amount of time to delay the operation (mostly memcached-specific)
         */
        abstract public function delete( $key, $time = 0 );

        public function lock( $key, $timeout = 0 ) {
                /* stub */
                return true;
        }

        public function unlock( $key ) {
                /* stub */
                return true;
        }

        public function keys() {
                /* stub */
                return array();
        }

        /* *** Emulated functions *** */
        /* Better performance can likely be got with custom written versions */
        public function get_multi( $keys ) {
                $out = array();
                foreach ( $keys as $key ) {
                        $out[$key] = $this->get( $key );
                }
                return $out;
        }

        public function set_multi( $hash, $exptime = 0 ) {
                foreach ( $hash as $key => $value ) {
                        $this->set( $key, $value, $exptime );
                }
        }

        public function add( $key, $value, $exptime = 0 ) {
                if ( $this->get( $key ) == false ) {
                        $this->set( $key, $value, $exptime );
                        return true;
                }
        }

        public function add_multi( $hash, $exptime = 0 ) {
                foreach ( $hash as $key => $value ) {
                        $this->add( $key, $value, $exptime );
                }
        }

        public function delete_multi( $keys, $time = 0 ) {
                foreach ( $keys as $key ) {
                        $this->delete( $key, $time );
                }
        }

        public function replace( $key, $value, $exptime = 0 ) {
                if ( $this->get( $key ) !== false ) {
                        $this->set( $key, $value, $exptime );
                }
        }

        public function incr( $key, $value = 1 ) {
                if ( !$this->lock( $key ) ) {
                        return false;
                }
                $value = intval( $value );

                $n = false;
                if ( ( $n = $this->get( $key ) ) !== false ) {
                        $n += $value;
                        $this->set( $key, $n ); // exptime?
                }
                $this->unlock( $key );
                return $n;
        }

        public function decr( $key, $value = 1 ) {
                return $this->incr( $key, -$value );
        }

        public function debug( $text ) {
                if ( $this->debugMode )
                        wfDebug( "BagOStuff debug: $text\n" );
        }

        /**
         * Convert an optionally relative time to an absolute time
         */
        protected function convertExpiry( $exptime ) {
                if ( ( $exptime != 0 ) && ( $exptime < 3600 * 24 * 30 ) ) {
                        return time() + $exptime;
                } else {
                        return $exptime;
                }
        }
}


/**
 * Functional versions!
 * This is a test of the interface, mainly. It stores things in an associative
 * array, which is not going to persist between program runs.
 *
 * @ingroup Cache
 */
class HashBagOStuff extends BagOStuff {
        var $bag;

        function __construct() {
                $this->bag = array();
        }

        protected function expire( $key ) {
                $et = $this->bag[$key][1];
                if ( ( $et == 0 ) || ( $et > time() ) ) {
                        return false;
                }
                $this->delete( $key );
                return true;
        }

        function get( $key ) {
                if ( !isset( $this->bag[$key] ) ) {
                        return false;
                }
                if ( $this->expire( $key ) ) {
                        return false;
                }
                return $this->bag[$key][0];
        }

        function set( $key, $value, $exptime = 0 ) {
                $this->bag[$key] = array( $value, $this->convertExpiry( $exptime ) );
        }

        function delete( $key, $time = 0 ) {
                if ( !isset( $this->bag[$key] ) ) {
                        return false;
                }
                unset( $this->bag[$key] );
                return true;
        }

        function keys() {
                return array_keys( $this->bag );
        }
}

/**
 * Class to store objects in the database
 *
 * @ingroup Cache
 */
class SqlBagOStuff extends BagOStuff {
        var $lb, $db;
        var $lastExpireAll = 0;

        protected function getDB() {
                if ( !isset( $this->lb ) ) {
                        $this->lb = wfGetLBFactory()->newMainLB();
                        $this->db = $this->lb->getConnection( DB_MASTER );
                        $this->db->clearFlag( DBO_TRX );
                }
                return $this->db;
        }

        public function get( $key ) {
                # expire old entries if any
                $this->garbageCollect();
                $db = $this->getDB();
                $row = $db->selectRow( 'objectcache', array( 'value', 'exptime' ),
                        array( 'keyname' => $key ), __METHOD__ );
                if ( !$row ) {
                        $this->debug( 'get: no matching rows' );
                        return false;
                }

                $this->debug( "get: retrieved data; expiry time is " . $row->exptime );
                if ( $this->isExpired( $row->exptime ) ) {
                        $this->debug( "get: key has expired, deleting" );
                        try {
                                $db->begin();
                                # Put the expiry time in the WHERE condition to avoid deleting a 
                                # newly-inserted value
                                $db->delete( 'objectcache', 
                                        array( 
                                                'keyname' => $key,
                                                'exptime' => $row->exptime
                                        ), __METHOD__ );
                                $db->commit();
                        } catch ( DBQueryError $e ) {
                                $this->handleWriteError( $e );
                        }
                        return false;
                }
                return $this->unserialize( $db->decodeBlob( $row->value ) );
        }

        public function set( $key, $value, $exptime = 0 ) {
                $db = $this->getDB();
                $exptime = intval( $exptime );
                if ( $exptime < 0 ) $exptime = 0;
                if ( $exptime == 0 ) {
                        $encExpiry = $this->getMaxDateTime();
                } else {
                        if ( $exptime < 3.16e8 ) # ~10 years
                                $exptime += time();
                        $encExpiry = $db->timestamp( $exptime );
                }
                try {
                        $db->begin();
                        $db->delete( 'objectcache', array( 'keyname' => $key ), __METHOD__ );
                        $db->insert( 'objectcache', 
                                array( 
                                        'keyname' => $key,
                                        'value' => $db->encodeBlob( $this->serialize( $value ) ),
                                        'exptime' => $encExpiry
                                ), __METHOD__ );
                        $db->commit();
                } catch ( DBQueryError $e ) {
                        $this->handleWriteError( $e );
                        return false;
                }
                return true;
        }

        public function delete( $key, $time = 0 ) {
                $db = $this->getDB();
                try {
                        $db->begin();
                        $db->delete( 'objectcache', array( 'keyname' => $key ), __METHOD__ );
                        $db->commit();
                } catch ( DBQueryError $e ) {
                        $this->handleWriteError( $e );
                        return false;
                }
                return true;
        }

        public function incr( $key, $step = 1 ) {
                $db = $this->getDB();
                $step = intval( $step );

                try {
                        $db->begin();
                        $row = $db->selectRow( 'objectcache', array( 'value', 'exptime' ),
                                array( 'keyname' => $key ), __METHOD__, array( 'FOR UPDATE' ) );
                        if ( $row === false ) {
                                // Missing
                                $db->commit();
                                return false;
                        }
                        $db->delete( 'objectcache', array( 'keyname' => $key ), __METHOD__ );
                        if ( $this->isExpired( $row->exptime ) ) {
                                // Expired, do not reinsert
                                $db->commit();
                                return false;
                        }

                        $oldValue = intval( $this->unserialize( $db->decodeBlob( $row->value ) ) );
                        $newValue = $oldValue + $step;
                        $db->insert( 'objectcache',
                                array(
                                        'keyname' => $key,
                                        'value' => $db->encodeBlob( $this->serialize( $newValue ) ),
                                        'exptime' => $row->exptime
                                ), __METHOD__ );
                        $db->commit();
                } catch ( DBQueryError $e ) {
                        $this->handleWriteError( $e );
                        return false;
                }
                return $newValue;
        }

        public function keys() {
                $db = $this->getDB();
                $res = $db->select( 'objectcache', array( 'keyname' ), false, __METHOD__ );     
                $result = array();
                foreach ( $res as $row ) {
                        $result[] = $row->keyname;
                }
                return $result;
        }

        protected function isExpired( $exptime ) {
                return $exptime != $this->getMaxDateTime() && wfTimestamp( TS_UNIX, $exptime ) < time();
        }

        protected function getMaxDateTime() {
                if ( time() > 0x7fffffff ) {
                        return $this->getDB()->timestamp( 1 << 62 );
                } else {
                        return $this->getDB()->timestamp( 0x7fffffff );
                }
        }

        protected function garbageCollect() {
                /* Ignore 99% of requests */
                if ( !mt_rand( 0, 100 ) ) {
                        $now = time();
                        /* Avoid repeating the delete within a few seconds */
                        if ( $now > ( $this->lastExpireAll + 1 ) ) {
                                $this->lastExpireAll = $now;
                                $this->expireAll();
                        }
                }
        }

        public function expireAll() {
                $db = $this->getDB();
                $now = $db->timestamp();
                try {
                        $db->begin();
                        $db->delete( 'objectcache', array( 'exptime < ' . $db->addQuotes( $now ) ), __METHOD__ );
                        $db->commit();
                } catch ( DBQueryError $e ) {
                        $this->handleWriteError( $e );
                }
        }

        public function deleteAll() {
                $db = $this->getDB();
                try {
                        $db->begin();
                        $db->delete( 'objectcache', '*', __METHOD__ );
                        $db->commit();
                } catch ( DBQueryError $e ) {
                        $this->handleWriteError( $e );
                }
        }

        /**
         * Serialize an object and, if possible, compress the representation.
         * On typical message and page data, this can provide a 3X decrease
         * in storage requirements.
         *
         * @param $data mixed
         * @return string
         */
        protected function serialize( &$data ) {
                $serial = serialize( $data );
                if ( function_exists( 'gzdeflate' ) ) {
                        return gzdeflate( $serial );
                } else {
                        return $serial;
                }
        }

        /**
         * Unserialize and, if necessary, decompress an object.
         * @param $serial string
         * @return mixed
         */
        protected function unserialize( $serial ) {
                if ( function_exists( 'gzinflate' ) ) {
                        $decomp = @gzinflate( $serial );
                        if ( false !== $decomp ) {
                                $serial = $decomp;
                        }
                }
                $ret = unserialize( $serial );
                return $ret;
        }

        /**
         * Handle a DBQueryError which occurred during a write operation.
         * Ignore errors which are due to a read-only database, rethrow others.
         */
        protected function handleWriteError( $exception ) {
                $db = $this->getDB();
                if ( !$db->wasReadOnlyError() ) {
                        throw $exception;
                }
                try {
                        $db->rollback();
                } catch ( DBQueryError $e ) {
                }
                wfDebug( __METHOD__ . ": ignoring query error\n" );
                $db->ignoreErrors( false );
        }
}

/**
 * Backwards compatibility alias
 */
class MediaWikiBagOStuff extends SqlBagOStuff {}

/**
 * This is a wrapper for Turck MMCache's shared memory functions.
 *
 * You can store objects with mmcache_put() and mmcache_get(), but Turck seems
 * to use a weird custom serializer that randomly segfaults. So we wrap calls
 * with serialize()/unserialize().
 *
 * The thing I noticed about the Turck serialized data was that unlike ordinary
 * serialize(), it contained the names of methods, and judging by the amount of
 * binary data, perhaps even the bytecode of the methods themselves. It may be
 * that Turck's serializer is faster, so a possible future extension would be
 * to use it for arrays but not for objects.
 *
 * @ingroup Cache
 */
class TurckBagOStuff extends BagOStuff {
        public function get( $key ) {
                $val = mmcache_get( $key );
                if ( is_string( $val ) ) {
                        $val = unserialize( $val );
                }
                return $val;
        }

        public function set( $key, $value, $exptime = 0 ) {
                mmcache_put( $key, serialize( $value ), $exptime );
                return true;
        }

        public function delete( $key, $time = 0 ) {
                mmcache_rm( $key );
                return true;
        }

        public function lock( $key, $waitTimeout = 0 ) {
                mmcache_lock( $key );
                return true;
        }

        public function unlock( $key ) {
                mmcache_unlock( $key );
                return true;
        }
}

/**
 * This is a wrapper for APC's shared memory functions
 *
 * @ingroup Cache
 */
class APCBagOStuff extends BagOStuff {
        public function get( $key ) {
                $val = apc_fetch( $key );
                if ( is_string( $val ) ) {
                        $val = unserialize( $val );
                }
                return $val;
        }

        public function set( $key, $value, $exptime = 0 ) {
                apc_store( $key, serialize( $value ), $exptime );
                return true;
        }

        public function delete( $key, $time = 0 ) {
                apc_delete( $key );
                return true;
        }
}


/**
 * This is a wrapper for eAccelerator's shared memory functions.
 *
 * This is basically identical to the Turck MMCache version,
 * mostly because eAccelerator is based on Turck MMCache.
 *
 * @ingroup Cache
 */
class eAccelBagOStuff extends BagOStuff {
        public function get( $key ) {
                $val = eaccelerator_get( $key );
                if ( is_string( $val ) ) {
                        $val = unserialize( $val );
                }
                return $val;
        }

        public function set( $key, $value, $exptime = 0 ) {
                eaccelerator_put( $key, serialize( $value ), $exptime );
                return true;
        }

        public function delete( $key, $time = 0 ) {
                eaccelerator_rm( $key );
                return true;
        }

        public function lock( $key, $waitTimeout = 0 ) {
                eaccelerator_lock( $key );
                return true;
        }

        public function unlock( $key ) {
                eaccelerator_unlock( $key );
                return true;
        }
}

/**
 * Wrapper for XCache object caching functions; identical interface
 * to the APC wrapper
 *
 * @ingroup Cache
 */
class XCacheBagOStuff extends BagOStuff {

        /**
         * Get a value from the XCache object cache
         *
         * @param $key String: cache key
         * @return mixed
         */
        public function get( $key ) {
                $val = xcache_get( $key );
                if ( is_string( $val ) )
                        $val = unserialize( $val );
                return $val;
        }

        /**
         * Store a value in the XCache object cache
         *
         * @param $key String: cache key
         * @param $value Mixed: object to store
         * @param $expire Int: expiration time
         * @return bool
         */
        public function set( $key, $value, $expire = 0 ) {
                xcache_set( $key, serialize( $value ), $expire );
                return true;
        }

        /**
         * Remove a value from the XCache object cache
         *
         * @param $key String: cache key
         * @param $time Int: not used in this implementation
         * @return bool
         */
        public function delete( $key, $time = 0 ) {
                xcache_unset( $key );
                return true;
        }

}

/**
 * Cache that uses DBA as a backend. 
 * Slow due to the need to constantly open and close the file to avoid holding 
 * writer locks. Intended for development use only,  as a memcached workalike 
 * for systems that don't have it.
 *
 * @ingroup Cache
 */
class DBABagOStuff extends BagOStuff {
        var $mHandler, $mFile, $mReader, $mWriter, $mDisabled;

        public function __construct( $handler = 'db3', $dir = false ) {
                if ( $dir === false ) {
                        global $wgTmpDirectory;
                        $dir = $wgTmpDirectory;
                }
                $this->mFile = "$dir/mw-cache-" . wfWikiID();
                $this->mFile .= '.db';
                wfDebug( __CLASS__ . ": using cache file {$this->mFile}\n" );
                $this->mHandler = $handler;
        }

        /**
         * Encode value and expiry for storage
         */
        function encode( $value, $expiry ) {
                # Convert to absolute time
                $expiry = $this->convertExpiry( $expiry );
                return sprintf( '%010u', intval( $expiry ) ) . ' ' . serialize( $value );
        }

        /**
         * @return list containing value first and expiry second
         */
        function decode( $blob ) {
                if ( !is_string( $blob ) ) {
                        return array( null, 0 );
                } else {
                        return array(
                                unserialize( substr( $blob, 11 ) ),
                                intval( substr( $blob, 0, 10 ) )
                        );
                }
        }

        function getReader() {
                if ( file_exists( $this->mFile ) ) {
                        $handle = dba_open( $this->mFile, 'rl', $this->mHandler );
                } else {
                        $handle = $this->getWriter();
                }
                if ( !$handle ) {
                        wfDebug( "Unable to open DBA cache file {$this->mFile}\n" );
                }
                return $handle;
        }

        function getWriter() {
                $handle = dba_open( $this->mFile, 'cl', $this->mHandler );
                if ( !$handle ) {
                        wfDebug( "Unable to open DBA cache file {$this->mFile}\n" );
                }
                return $handle;
        }

        function get( $key ) {
                wfProfileIn( __METHOD__ );
                wfDebug( __METHOD__ . "($key)\n" );
                $handle = $this->getReader();
                if ( !$handle ) {
                        return null;
                }
                $val = dba_fetch( $key, $handle );
                list( $val, $expiry ) = $this->decode( $val );
                # Must close ASAP because locks are held
                dba_close( $handle );

                if ( !is_null( $val ) && $expiry && $expiry < time() ) {
                        # Key is expired, delete it
                        $handle = $this->getWriter();
                        dba_delete( $key, $handle );
                        dba_close( $handle );
                        wfDebug( __METHOD__ . ": $key expired\n" );
                        $val = null;
                }
                wfProfileOut( __METHOD__ );
                return $val;
        }

        function set( $key, $value, $exptime = 0 ) {
                wfProfileIn( __METHOD__ );
                wfDebug( __METHOD__ . "($key)\n" );
                $blob = $this->encode( $value, $exptime );
                $handle = $this->getWriter();
                if ( !$handle ) {
                        return false;
                }
                $ret = dba_replace( $key, $blob, $handle );
                dba_close( $handle );
                wfProfileOut( __METHOD__ );
                return $ret;
        }

        function delete( $key, $time = 0 ) {
                wfProfileIn( __METHOD__ );
                wfDebug( __METHOD__ . "($key)\n" );
                $handle = $this->getWriter();
                if ( !$handle ) {
                        return false;
                }
                $ret = dba_delete( $key, $handle );
                dba_close( $handle );
                wfProfileOut( __METHOD__ );
                return $ret;
        }

        function add( $key, $value, $exptime = 0 ) {
                wfProfileIn( __METHOD__ );
                $blob = $this->encode( $value, $exptime );
                $handle = $this->getWriter();
                if ( !$handle ) {
                        return false;
                }
                $ret = dba_insert( $key, $blob, $handle );
                # Insert failed, check to see if it failed due to an expired key
                if ( !$ret ) {
                        list( $value, $expiry ) = $this->decode( dba_fetch( $key, $handle ) );
                        if ( $expiry < time() ) {
                                # Yes expired, delete and try again
                                dba_delete( $key, $handle );
                                $ret = dba_insert( $key, $blob, $handle );
                                # This time if it failed then it will be handled by the caller like any other race
                        }
                }

                dba_close( $handle );
                wfProfileOut( __METHOD__ );
                return $ret;
        }

        function keys() {
                $reader = $this->getReader();
                $k1 = dba_firstkey( $reader );
                if ( !$k1 ) {
                        return array();
                }
                $result[] = $k1;
                while ( $key = dba_nextkey( $reader ) ) {
                        $result[] = $key;
                }
                return $result;
        }
}