--- /dev/null
+<?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
+ */
+
+use Wikimedia\Rdbms\LoadBalancer;
+use Wikimedia\Rdbms\IDatabase;
+use Wikimedia\Rdbms\DBConnRef;
+use Wikimedia\Rdbms\MaintainableDBConnRef;
+
+/**
+ * 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 provided URL is in the form of DB://cluster/id
+ * or DB://cluster/id/itemid for concatened storage.
+ *
+ * @param string $url
+ * @return string|bool False if missing
+ * @see ExternalStoreMedium::fetchFromURL()
+ */
+ public function fetchFromURL( $url ) {
+ list( $cluster, $id, $itemID ) = $this->parseURL( $url );
+ $ret = $this->fetchBlob( $cluster, $id, $itemID );
+
+ if ( $itemID !== false && $ret !== false ) {
+ return $ret->getItem( $itemID );
+ }
+
+ return $ret;
+ }
+
+ /**
+ * Fetch data from given external store URLs.
+ * The provided URLs are in the form of DB://cluster/id
+ * or DB://cluster/id/itemid for concatened storage.
+ *
+ * @param array $urls An array of external store URLs
+ * @return array A map from url to stored content. Failed results
+ * are not represented.
+ */
+ public function batchFetchFromURLs( array $urls ) {
+ $batched = $inverseUrlMap = [];
+ foreach ( $urls as $url ) {
+ list( $cluster, $id, $itemID ) = $this->parseURL( $url );
+ $batched[$cluster][$id][] = $itemID;
+ // false $itemID gets cast to int, but should be ok
+ // since we do === from the $itemID in $batched
+ $inverseUrlMap[$cluster][$id][$itemID] = $url;
+ }
+ $ret = [];
+ foreach ( $batched as $cluster => $batchByCluster ) {
+ $res = $this->batchFetchBlobs( $cluster, $batchByCluster );
+ /** @var HistoryBlob $blob */
+ foreach ( $res as $id => $blob ) {
+ foreach ( $batchByCluster[$id] as $itemID ) {
+ $url = $inverseUrlMap[$cluster][$id][$itemID];
+ if ( $itemID === false ) {
+ $ret[$url] = $blob;
+ } else {
+ $ret[$url] = $blob->getItem( $itemID );
+ }
+ }
+ }
+ }
+
+ return $ret;
+ }
+
+ public function store( $location, $data ) {
+ $dbw = $this->getMaster( $location );
+ $dbw->insert( $this->getTable( $dbw ),
+ [ 'blob_text' => $data ],
+ __METHOD__ );
+ $id = $dbw->insertId();
+ if ( !$id ) {
+ throw new MWException( __METHOD__ . ': no insert ID' );
+ }
+
+ return "DB://$location/$id";
+ }
+
+ /**
+ * Get a LoadBalancer for the specified cluster
+ *
+ * @param string $cluster Cluster name
+ * @return LoadBalancer
+ */
+ private function getLoadBalancer( $cluster ) {
+ return wfGetLBFactory()->getExternalLB( $cluster );
+ }
+
+ /**
+ * Get a replica DB connection for the specified cluster
+ *
+ * @param string $cluster Cluster name
+ * @return DBConnRef
+ */
+ public 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\n" );
+ $lb->allowLagged( true );
+ } else {
+ wfDebug( "writable external store\n" );
+ }
+
+ $db = $lb->getConnectionRef( DB_REPLICA, [], $wiki );
+ $db->clearFlag( DBO_TRX ); // sanity
+
+ return $db;
+ }
+
+ /**
+ * Get a master database connection for the specified cluster
+ *
+ * @param string $cluster Cluster name
+ * @return MaintainableDBConnRef
+ */
+ public function getMaster( $cluster ) {
+ $wiki = isset( $this->params['wiki'] ) ? $this->params['wiki'] : false;
+ $lb = $this->getLoadBalancer( $cluster );
+
+ $db = $lb->getMaintenanceConnectionRef( DB_MASTER, [], $wiki );
+ $db->clearFlag( DBO_TRX ); // sanity
+
+ return $db;
+ }
+
+ /**
+ * Get the 'blobs' table name for this database
+ *
+ * @param IDatabase $db
+ * @return string Table name ('blobs' by default)
+ */
+ public 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 string $cluster
+ * @param string $id
+ * @param string $itemID
+ * @return HistoryBlob|bool Returns false if missing
+ */
+ 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 = [];
+
+ $cacheID = ( $itemID === false ) ? "$cluster/$id" : "$cluster/$id/";
+ if ( isset( $externalBlobCache[$cacheID] ) ) {
+ wfDebugLog( 'ExternalStoreDB-cache',
+ "ExternalStoreDB::fetchBlob cache hit on $cacheID" );
+
+ return $externalBlobCache[$cacheID];
+ }
+
+ wfDebugLog( 'ExternalStoreDB-cache',
+ "ExternalStoreDB::fetchBlob cache miss on $cacheID" );
+
+ $dbr = $this->getSlave( $cluster );
+ $ret = $dbr->selectField( $this->getTable( $dbr ),
+ 'blob_text', [ 'blob_id' => $id ], __METHOD__ );
+ if ( $ret === false ) {
+ wfDebugLog( 'ExternalStoreDB',
+ "ExternalStoreDB::fetchBlob master fallback on $cacheID" );
+ // Try the master
+ $dbw = $this->getMaster( $cluster );
+ $ret = $dbw->selectField( $this->getTable( $dbw ),
+ 'blob_text', [ 'blob_id' => $id ], __METHOD__ );
+ if ( $ret === false ) {
+ wfDebugLog( 'ExternalStoreDB',
+ "ExternalStoreDB::fetchBlob master failed to find $cacheID" );
+ }
+ }
+ if ( $itemID !== false && $ret !== false ) {
+ // Unserialise object; caller extracts item
+ $ret = unserialize( $ret );
+ }
+
+ $externalBlobCache = [ $cacheID => $ret ];
+
+ return $ret;
+ }
+
+ /**
+ * Fetch multiple blob items out of the database
+ *
+ * @param string $cluster A cluster name valid for use with LBFactory
+ * @param array $ids A map from the blob_id's to look for to the requested itemIDs in the blobs
+ * @return array A map from the blob_id's requested to their content.
+ * Unlocated ids are not represented
+ */
+ private function batchFetchBlobs( $cluster, array $ids ) {
+ $dbr = $this->getSlave( $cluster );
+ $res = $dbr->select( $this->getTable( $dbr ),
+ [ 'blob_id', 'blob_text' ], [ 'blob_id' => array_keys( $ids ) ], __METHOD__ );
+ $ret = [];
+ if ( $res !== false ) {
+ $this->mergeBatchResult( $ret, $ids, $res );
+ }
+ if ( $ids ) {
+ wfDebugLog( __CLASS__, __METHOD__ .
+ " master fallback on '$cluster' for: " .
+ implode( ',', array_keys( $ids ) ) );
+ // Try the master
+ $dbw = $this->getMaster( $cluster );
+ $res = $dbw->select( $this->getTable( $dbr ),
+ [ 'blob_id', 'blob_text' ],
+ [ 'blob_id' => array_keys( $ids ) ],
+ __METHOD__ );
+ if ( $res === false ) {
+ wfDebugLog( __CLASS__, __METHOD__ . " master failed on '$cluster'" );
+ } else {
+ $this->mergeBatchResult( $ret, $ids, $res );
+ }
+ }
+ if ( $ids ) {
+ wfDebugLog( __CLASS__, __METHOD__ .
+ " master on '$cluster' failed locating items: " .
+ implode( ',', array_keys( $ids ) ) );
+ }
+
+ return $ret;
+ }
+
+ /**
+ * Helper function for self::batchFetchBlobs for merging master/replica DB results
+ * @param array &$ret Current self::batchFetchBlobs return value
+ * @param array &$ids Map from blob_id to requested itemIDs
+ * @param mixed $res DB result from Database::select
+ */
+ private function mergeBatchResult( array &$ret, array &$ids, $res ) {
+ foreach ( $res as $row ) {
+ $id = $row->blob_id;
+ $itemIDs = $ids[$id];
+ unset( $ids[$id] ); // to track if everything is found
+ if ( count( $itemIDs ) === 1 && reset( $itemIDs ) === false ) {
+ // single result stored per blob
+ $ret[$id] = $row->blob_text;
+ } else {
+ // multi result stored per blob
+ $ret[$id] = unserialize( $row->blob_text );
+ }
+ }
+ }
+
+ /**
+ * @param string $url
+ * @return array
+ */
+ protected function parseURL( $url ) {
+ $path = explode( '/', $url );
+
+ return [
+ $path[2], // cluster
+ $path[3], // id
+ isset( $path[4] ) ? $path[4] : false // itemID
+ ];
+ }
+}
scripts.mit.edu / autoinstallsdev / mediawiki.git / blobdiff