<?php
-/**
- *
- * @package MediaWiki
- *
- * DB accessable external objects
- *
- */
-require_once( 'LoadBalancer.php' );
-
-
-/** @package MediaWiki */
/**
* External database storage will use one (or more) separate connection pools
global $wgExternalBlobCache;
$wgExternalBlobCache = array();
+/**
+ * DB accessable external objects
+ * @ingroup ExternalStorage
+ */
class ExternalStoreDB {
- /**
- * Fetch data from given URL
- * @param string $url An url
- */
+ /** @todo Document.*/
function &getLoadBalancer( $cluster ) {
- global $wgExternalServers, $wgExternalLoadBalancers;
- if ( !array_key_exists( $cluster, $wgExternalLoadBalancers ) ) {
- $wgExternalLoadBalancers[$cluster] = LoadBalancer::newFromParams( $wgExternalServers[$cluster] );
- }
- return $wgExternalLoadBalancers[$cluster];
+ return wfGetLBFactory()->getExternalLB( $cluster );
}
-
+
+ /** @todo Document.*/
function &getSlave( $cluster ) {
$lb =& $this->getLoadBalancer( $cluster );
- return $lb->getConnection( DB_SLAVE );
+ // Make only two connection attempts, since we still have the master to try
+ return $lb->getConnection( DB_SLAVE, array(), false, 2 );
}
- function &getMaster( $cluster ) {
+ /** @todo Document.*/
+ function &getMaster( $cluster, $retry = true ) {
$lb =& $this->getLoadBalancer( $cluster );
- return $lb->getConnection( DB_MASTER );
- }
+ // Make only two connection attempts if there are other clusters to try
+ $attempts = $retry ? false : 2;
+ return $lb->getConnection( DB_MASTER, array(), false, $attempts, LoadBalancer::GRACEFUL );
+ }
+ /** @todo Document.*/
function getTable( &$db ) {
$table = $db->getLBInfo( 'blobs table' );
if ( is_null( $table ) ) {
}
return $table;
}
-
- function fetchFromURL($url) {
- global $wgExternalServers;
- #
- # URLs have the form DB://cluster/id or DB://cluster/id/itemid for concatenated storage
- #
+
+ /**
+ * 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 ) {
$path = explode( '/', $url );
$cluster = $path[2];
$id = $path[3];
$ret =& $this->fetchBlob( $cluster, $id, $itemID );
- if ( $itemID !== false ) {
+ if ( $itemID !== false && $ret !== false ) {
return $ret->getItem( $itemID );
}
return $ret;
}
-
+
/**
* 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
- * @access private
+ * @private
*/
function &fetchBlob( $cluster, $id, $itemID ) {
global $wgExternalBlobCache;
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( $itemID !== false ) {
+ 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 string $cluster The cluster name
- * @param string $data The data item
+ * @param $cluster String: the cluster name
+ * @param $data String: the data item
+ * @param $retry bool: allows an extra DB connection retry after 1 second
* @return string URL
*/
- function store( $cluster, $data ) {
- global $wgExternalServers;
- $fname = 'ExternalStoreDB::store';
-
- $dbw =& $this->getMaster( $cluster );
-
+ function store( $cluster, $data, $retry = true ) {
+ if( !$dbw = $this->getMaster( $cluster, $retry ) ) {
+ return false; // failed, maybe another cluster is up...
+ }
$id = $dbw->nextSequenceValue( 'blob_blob_id_seq' );
- $dbw->insert( $this->getTable( $dbw ), array( 'blob_id' => $id, 'blob_text' => $data ), $fname );
- return "DB://$cluster/" . $dbw->insertId();
+ $dbw->insert( $this->getTable( $dbw ),
+ array( 'blob_id' => $id, 'blob_text' => $data ),
+ __METHOD__ );
+ $id = $dbw->insertId();
+ if ( $dbw->getFlag( DBO_TRX ) ) {
+ $dbw->immediateCommit();
+ }
+ return "DB://$cluster/$id";
}
}
-?>