* Changed password hash format, see wikitech-l

[lhc/web/wiklou.git] / includes / ExternalStoreDB.php

diff --git a/includes/ExternalStoreDB.php b/includes/ExternalStoreDB.php
index 9d12dc6..549412d 100644 (file)
--- a/includes/ExternalStoreDB.php
+++ b/includes/ExternalStoreDB.php
@@ -1,37 +1,137 @@
 <?php
+
 /**
- * 
- * @package MediaWiki
+ * External database storage will use one (or more) separate connection pools
+ * from what the main wiki uses. If we load many revisions, such as when doing
+ * bulk backups or maintenance, we want to keep them around over the lifetime
+ * of the script.
  *
+ * Associative array of LoadBalancer objects, indexed by cluster name.
+ */
+global $wgExternalLoadBalancers;
+$wgExternalLoadBalancers = array();
+
+/**
+ * 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.
+ */
+global $wgExternalBlobCache;
+$wgExternalBlobCache = array();
+
+/**
  * DB accessable external objects
- *
+ * @ingroup ExternalStorage
  */
-require_once( 'LoadBalancer.php' ); 
+class ExternalStoreDB {
 
+       /** @todo Document.*/
+       function &getLoadBalancer( $cluster ) {
+               return wfGetLBFactory()->getExternalLB( $cluster );
+       }
 
+       /** @todo Document.*/
+       function &getSlave( $cluster ) {
+               $lb =& $this->getLoadBalancer( $cluster );
+               return $lb->getConnection( DB_SLAVE );
+       }
 
-class ExternalStoreDB {
-       /* Fetch data from given URL */
+       /** @todo Document.*/
+       function &getMaster( $cluster ) {
+               $lb =& $this->getLoadBalancer( $cluster );
+               return $lb->getConnection( DB_MASTER );
+       }
+
+       /** @todo Document.*/
+       function getTable( &$db ) {
+               $table = $db->getLBInfo( 'blobs table' );
+               if ( is_null( $table ) ) {
+                       $table = 'blobs';
+               }
+               return $table;
+       }
+
+       /**
+        * Fetch data from given URL
+        * @param string $url An url of the form DB://cluster/id or DB://cluster/id/itemid for concatened storage.
+        */
        function fetchFromURL($url) {
-               global $wgExternalServers;
-               #
-               # URLs have the form DB://cluster/id, e.g.
-               # DB://cluster1/3298247
-               #
                $path = explode( '/', $url );
                $cluster  = $path[2];
                $id       = $path[3];
+               if ( isset( $path[4] ) ) {
+                       $itemID = $path[4];
+               } else {
+                       $itemID = false;
+               }
 
-               $lb = LoadBalancer::NewFromParams( $wgExternalServers[$cluster] );
-               $db = $lb->getConnection( DB_SLAVE );
+               $ret =& $this->fetchBlob( $cluster, $id, $itemID );
 
-               $ret = $db->selectField( 'blobs', 'blob_text', array( 'blob_id' => $id ) ); 
-               
+               if ( $itemID !== false && $ret !== false ) {
+                       return $ret->getItem( $itemID );
+               }
                return $ret;
        }
 
-       /* XXX: may require other methods, for store, delete, 
-        * whatever, for initial ext storage  
+       /**
+        * 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 ) {
+               global $wgExternalBlobCache;
+               $cacheID = ( $itemID === false ) ? "$cluster/$id" : "$cluster/$id/";
+               if( isset( $wgExternalBlobCache[$cacheID] ) ) {
+                       wfDebug( "ExternalStoreDB::fetchBlob cache hit on $cacheID\n" );
+                       return $wgExternalBlobCache[$cacheID];
+               }
+
+               wfDebug( "ExternalStoreDB::fetchBlob cache miss on $cacheID\n" );
+
+               $dbr =& $this->getSlave( $cluster );
+               $ret = $dbr->selectField( $this->getTable( $dbr ), 'blob_text', array( 'blob_id' => $id ) );
+               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 ) );
+                       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 );
+               }
+
+               $wgExternalBlobCache = array( $cacheID => &$ret );
+               return $ret;
+       }
+
+       /**
+        * Insert a data item into a given cluster
+        *
+        * @param $cluster String: the cluster name
+        * @param $data String: the data item
+        * @return string URL
+        */
+       function store( $cluster, $data ) {
+               $fname = 'ExternalStoreDB::store';
+
+               $dbw =& $this->getMaster( $cluster );
+
+               $id = $dbw->nextSequenceValue( 'blob_blob_id_seq' );
+               $dbw->insert( $this->getTable( $dbw ), array( 'blob_id' => $id, 'blob_text' => $data ), $fname );
+               $id = $dbw->insertId();
+               if ( $dbw->getFlag( DBO_TRX ) ) {
+                       $dbw->immediateCommit();
+               }
+               return "DB://$cluster/$id";
+       }
 }
-?>