141 lines
3.8 KiB
PHP
141 lines
3.8 KiB
PHP
<?php
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/**
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*
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*
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* DB accessable external objects
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*
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*/
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/**
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* External database storage will use one (or more) separate connection pools
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* from what the main wiki uses. If we load many revisions, such as when doing
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* bulk backups or maintenance, we want to keep them around over the lifetime
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* of the script.
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*
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* Associative array of LoadBalancer objects, indexed by cluster name.
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*/
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global $wgExternalLoadBalancers;
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$wgExternalLoadBalancers = array();
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/**
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* One-step cache variable to hold base blobs; operations that
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* pull multiple revisions may often pull multiple times from
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* the same blob. By keeping the last-used one open, we avoid
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* redundant unserialization and decompression overhead.
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*/
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global $wgExternalBlobCache;
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$wgExternalBlobCache = array();
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class ExternalStoreDB {
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/** @todo Document.*/
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function &getLoadBalancer( $cluster ) {
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return wfGetLBFactory()->getExternalLB( $cluster );
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}
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/** @todo Document.*/
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function &getSlave( $cluster ) {
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$lb =& $this->getLoadBalancer( $cluster );
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return $lb->getConnection( DB_SLAVE );
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}
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/** @todo Document.*/
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function &getMaster( $cluster ) {
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$lb =& $this->getLoadBalancer( $cluster );
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return $lb->getConnection( DB_MASTER );
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}
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/** @todo Document.*/
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function getTable( &$db ) {
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$table = $db->getLBInfo( 'blobs table' );
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if ( is_null( $table ) ) {
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$table = 'blobs';
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}
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return $table;
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}
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/**
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* Fetch data from given URL
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* @param string $url An url of the form DB://cluster/id or DB://cluster/id/itemid for concatened storage.
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*/
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function fetchFromURL($url) {
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$path = explode( '/', $url );
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$cluster = $path[2];
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$id = $path[3];
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if ( isset( $path[4] ) ) {
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$itemID = $path[4];
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} else {
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$itemID = false;
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}
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$ret =& $this->fetchBlob( $cluster, $id, $itemID );
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if ( $itemID !== false && $ret !== false ) {
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return $ret->getItem( $itemID );
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}
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return $ret;
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}
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/**
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* Fetch a blob item out of the database; a cache of the last-loaded
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* blob will be kept so that multiple loads out of a multi-item blob
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* can avoid redundant database access and decompression.
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* @param $cluster
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* @param $id
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* @param $itemID
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* @return mixed
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* @private
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*/
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function &fetchBlob( $cluster, $id, $itemID ) {
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global $wgExternalBlobCache;
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$cacheID = ( $itemID === false ) ? "$cluster/$id" : "$cluster/$id/";
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if( isset( $wgExternalBlobCache[$cacheID] ) ) {
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wfDebug( "ExternalStoreDB::fetchBlob cache hit on $cacheID\n" );
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return $wgExternalBlobCache[$cacheID];
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}
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wfDebug( "ExternalStoreDB::fetchBlob cache miss on $cacheID\n" );
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$dbr =& $this->getSlave( $cluster );
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$ret = $dbr->selectField( $this->getTable( $dbr ), 'blob_text', array( 'blob_id' => $id ) );
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if ( $ret === false ) {
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wfDebugLog( 'ExternalStoreDB', "ExternalStoreDB::fetchBlob master fallback on $cacheID\n" );
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// Try the master
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$dbw =& $this->getMaster( $cluster );
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$ret = $dbw->selectField( $this->getTable( $dbw ), 'blob_text', array( 'blob_id' => $id ) );
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if( $ret === false) {
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wfDebugLog( 'ExternalStoreDB', "ExternalStoreDB::fetchBlob master failed to find $cacheID\n" );
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}
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}
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if( $itemID !== false && $ret !== false ) {
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// Unserialise object; caller extracts item
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$ret = unserialize( $ret );
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}
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$wgExternalBlobCache = array( $cacheID => &$ret );
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return $ret;
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}
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/**
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* Insert a data item into a given cluster
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*
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* @param $cluster String: the cluster name
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* @param $data String: the data item
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* @return string URL
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*/
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function store( $cluster, $data ) {
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$fname = 'ExternalStoreDB::store';
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$dbw =& $this->getMaster( $cluster );
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$id = $dbw->nextSequenceValue( 'blob_blob_id_seq' );
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$dbw->insert( $this->getTable( $dbw ), array( 'blob_id' => $id, 'blob_text' => $data ), $fname );
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$id = $dbw->insertId();
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if ( $dbw->getFlag( DBO_TRX ) ) {
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$dbw->immediateCommit();
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}
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return "DB://$cluster/$id";
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}
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}
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