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Diffstat (limited to 'includes/externalstore/ExternalStoreDB.php')
| -rw-r--r-- | includes/externalstore/ExternalStoreDB.php | 181 |
1 files changed, 181 insertions, 0 deletions
diff --git a/includes/externalstore/ExternalStoreDB.php b/includes/externalstore/ExternalStoreDB.php new file mode 100644 index 00000000..196e7f2c --- /dev/null +++ b/includes/externalstore/ExternalStoreDB.php @@ -0,0 +1,181 @@ +<?php +/** + * External storage in SQL database. + * + * 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 + */ + +/** + * DB accessable external objects. + * + * In this system, each store "location" maps to a database "cluster". + * The clusters must be defined in the normal LBFactory configuration. + * + * @ingroup ExternalStorage + */ +class ExternalStoreDB extends ExternalStoreMedium { + /** + * The URL returned is of the form of the form DB://cluster/id + * or DB://cluster/id/itemid for concatened storage. + * + * @see ExternalStoreMedium::fetchFromURL() + */ + public function fetchFromURL( $url ) { + $path = explode( '/', $url ); + $cluster = $path[2]; + $id = $path[3]; + if ( isset( $path[4] ) ) { + $itemID = $path[4]; + } else { + $itemID = false; + } + + $ret =& $this->fetchBlob( $cluster, $id, $itemID ); + + if ( $itemID !== false && $ret !== false ) { + return $ret->getItem( $itemID ); + } + return $ret; + } + + /** + * @see ExternalStoreMedium::store() + */ + public function store( $cluster, $data ) { + $dbw = $this->getMaster( $cluster ); + $id = $dbw->nextSequenceValue( 'blob_blob_id_seq' ); + $dbw->insert( $this->getTable( $dbw ), + array( 'blob_id' => $id, 'blob_text' => $data ), + __METHOD__ ); + $id = $dbw->insertId(); + if ( !$id ) { + throw new MWException( __METHOD__.': no insert ID' ); + } + if ( $dbw->getFlag( DBO_TRX ) ) { + $dbw->commit( __METHOD__ ); + } + return "DB://$cluster/$id"; + } + + /** + * Get a LoadBalancer for the specified cluster + * + * @param string $cluster cluster name + * @return LoadBalancer object + */ + function &getLoadBalancer( $cluster ) { + $wiki = isset( $this->params['wiki'] ) ? $this->params['wiki'] : false; + + return wfGetLBFactory()->getExternalLB( $cluster, $wiki ); + } + + /** + * Get a slave database connection for the specified cluster + * + * @param string $cluster cluster name + * @return DatabaseBase object + */ + function &getSlave( $cluster ) { + global $wgDefaultExternalStore; + + $wiki = isset( $this->params['wiki'] ) ? $this->params['wiki'] : false; + $lb =& $this->getLoadBalancer( $cluster ); + + if ( !in_array( "DB://" . $cluster, (array)$wgDefaultExternalStore ) ) { + wfDebug( "read only external store" ); + $lb->allowLagged( true ); + } else { + wfDebug( "writable external store" ); + } + + return $lb->getConnection( DB_SLAVE, array(), $wiki ); + } + + /** + * Get a master database connection for the specified cluster + * + * @param string $cluster cluster name + * @return DatabaseBase object + */ + function &getMaster( $cluster ) { + $wiki = isset( $this->params['wiki'] ) ? $this->params['wiki'] : false; + $lb =& $this->getLoadBalancer( $cluster ); + return $lb->getConnection( DB_MASTER, array(), $wiki ); + } + + /** + * Get the 'blobs' table name for this database + * + * @param $db DatabaseBase + * @return String: table name ('blobs' by default) + */ + function getTable( &$db ) { + $table = $db->getLBInfo( 'blobs table' ); + if ( is_null( $table ) ) { + $table = 'blobs'; + } + return $table; + } + + /** + * Fetch a blob item out of the database; a cache of the last-loaded + * blob will be kept so that multiple loads out of a multi-item blob + * can avoid redundant database access and decompression. + * @param $cluster + * @param $id + * @param $itemID + * @return mixed + * @private + */ + function &fetchBlob( $cluster, $id, $itemID ) { + /** + * One-step cache variable to hold base blobs; operations that + * pull multiple revisions may often pull multiple times from + * the same blob. By keeping the last-used one open, we avoid + * redundant unserialization and decompression overhead. + */ + static $externalBlobCache = array(); + + $cacheID = ( $itemID === false ) ? "$cluster/$id" : "$cluster/$id/"; + if( isset( $externalBlobCache[$cacheID] ) ) { + wfDebugLog( 'ExternalStoreDB-cache', "ExternalStoreDB::fetchBlob cache hit on $cacheID\n" ); + return $externalBlobCache[$cacheID]; + } + + wfDebugLog( 'ExternalStoreDB-cache', "ExternalStoreDB::fetchBlob cache miss on $cacheID\n" ); + + $dbr =& $this->getSlave( $cluster ); + $ret = $dbr->selectField( $this->getTable( $dbr ), 'blob_text', array( 'blob_id' => $id ), __METHOD__ ); + if ( $ret === false ) { + wfDebugLog( 'ExternalStoreDB', "ExternalStoreDB::fetchBlob master fallback on $cacheID\n" ); + // Try the master + $dbw =& $this->getMaster( $cluster ); + $ret = $dbw->selectField( $this->getTable( $dbw ), 'blob_text', array( 'blob_id' => $id ), __METHOD__ ); + if( $ret === false) { + wfDebugLog( 'ExternalStoreDB', "ExternalStoreDB::fetchBlob master failed to find $cacheID\n" ); + } + } + if( $itemID !== false && $ret !== false ) { + // Unserialise object; caller extracts item + $ret = unserialize( $ret ); + } + + $externalBlobCache = array( $cacheID => &$ret ); + return $ret; + } +} |