5 files changed, 534 insertions, 0 deletions
diff --git a/includes/externalstore/ExternalStore.php b/includes/externalstore/ExternalStore.php
new file mode 100644
index 00000000..4ca193d4
--- /dev/null
+++ b/includes/externalstore/ExternalStore.php
@@ -0,0 +1,178 @@
+<?php
+/**
+ * @defgroup ExternalStorage ExternalStorage
+ */
+
+/**
+ * Interface for data storage in external repositories.
+ *
+ * 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
+ */
+
+/**
+ * Constructor class for key/value blob data kept in external repositories.
+ *
+ * Objects in external stores are defined by a special URL. The URL is of
+ * the form "<store protocol>://<location>/<object name>". The protocol is used
+ * to determine what ExternalStoreMedium class is used. The location identifies
+ * particular storage instances or database clusters for store class to use.
+ *
+ * When an object is inserted into a store, the calling code uses a partial URL of
+ * the form "<store protocol>://<location>" and receives the full object URL on success.
+ * This is useful since object names can be sequential IDs, UUIDs, or hashes.
+ * Callers are not responsible for unique name generation.
+ *
+ * External repositories might be populated by maintenance/async
+ * scripts, thus partial moving of data may be possible, as well
+ * as the possibility to have any storage format (i.e. for archives).
+ *
+ * @ingroup ExternalStorage
+ */
+class ExternalStore {
+	/**
+	 * Get an external store object of the given type, with the given parameters
+	 *
+	 * @param string $proto Type of external storage, should be a value in $wgExternalStores
+	 * @param array $params Associative array of ExternalStoreMedium parameters
+	 * @return ExternalStoreMedium|bool The store class or false on error
+	 */
+	public static function getStoreObject( $proto, array $params = array() ) {
+		global $wgExternalStores;
+
+		if ( !$wgExternalStores || !in_array( $proto, $wgExternalStores ) ) {
+			return false; // protocol not enabled
+		}
+
+		$class = 'ExternalStore' . ucfirst( $proto );
+		// Any custom modules should be added to $wgAutoLoadClasses for on-demand loading
+		return MWInit::classExists( $class ) ? new $class( $params ) : false;
+	}
+
+	/**
+	 * Fetch data from given URL
+	 *
+	 * @param string $url The URL of the text to get
+	 * @param array $params Associative array of ExternalStoreMedium parameters
+	 * @return string|bool The text stored or false on error
+	 * @throws MWException
+	 */
+	public static function fetchFromURL( $url, array $params = array() ) {
+		$parts = explode( '://', $url, 2 );
+		if ( count( $parts ) != 2 ) {
+			return false; // invalid URL
+		}
+
+		list( $proto, $path ) = $parts;
+		if ( $path == '' ) { // bad URL
+			return false;
+		}
+
+		$store = self::getStoreObject( $proto, $params );
+		if ( $store === false ) {
+			return false;
+		}
+
+		return $store->fetchFromURL( $url );
+	}
+
+	/**
+	 * Store a data item to an external store, identified by a partial URL
+	 * The protocol part is used to identify the class, the rest is passed to the
+	 * class itself as a parameter.
+	 *
+	 * @param string $url A partial external store URL ("<store type>://<location>")
+	 * @param $data string
+	 * @param array $params Associative array of ExternalStoreMedium parameters
+	 * @return string|bool The URL of the stored data item, or false on error
+	 * @throws MWException
+	 */
+	public static function insert( $url, $data, array $params = array() ) {
+		$parts = explode( '://', $url, 2 );
+		if ( count( $parts ) != 2 ) {
+			return false; // invalid URL
+		}
+
+		list( $proto, $path ) = $parts;
+		if ( $path == '' ) { // bad URL
+			return false;
+		}
+
+		$store = self::getStoreObject( $proto, $params );
+		if ( $store === false ) {
+			return false;
+		} else {
+			return $store->store( $path, $data );
+		}
+	}
+
+	/**
+	 * Like insert() above, but does more of the work for us.
+	 * This function does not need a url param, it builds it by
+	 * itself. It also fails-over to the next possible clusters.
+	 *
+	 * @param $data string
+	 * @param array $params Associative array of ExternalStoreMedium parameters
+	 * @return string|bool The URL of the stored data item, or false on error
+	 * @throws MWException
+	 */
+	public static function insertToDefault( $data, array $params = array() ) {
+		global $wgDefaultExternalStore;
+
+		$error = false;
+		$tryStores = (array)$wgDefaultExternalStore;
+		while ( count( $tryStores ) > 0 ) {
+			$index = mt_rand( 0, count( $tryStores ) - 1 );
+			$storeUrl = $tryStores[$index];
+			wfDebug( __METHOD__ . ": trying $storeUrl\n" );
+			list( $proto, $path ) = explode( '://', $storeUrl, 2 );
+			$store = self::getStoreObject( $proto, $params );
+			if ( $store === false ) {
+				throw new MWException( "Invalid external storage protocol - $storeUrl" );
+			}
+			try {
+				$url = $store->store( $path, $data ); // Try to save the object
+			} catch ( MWException $error ) {
+				$url = false;
+			}
+			if ( strlen( $url ) ) {
+				return $url; // Done!
+			} else {
+				unset( $tryStores[$index] ); // Don't try this one again!
+				$tryStores = array_values( $tryStores ); // Must have consecutive keys
+				wfDebugLog( 'ExternalStorage',
+					"Unable to store text to external storage $storeUrl" );
+			}
+		}
+		// All stores failed
+		if ( $error ) {
+			throw $error; // rethrow the last error
+		} else {
+			throw new MWException( "Unable to store text to external storage" );
+		}
+	}
+
+	/**
+	 * @param $data string
+	 * @param $wiki string
+	 * @return string|bool The URL of the stored data item, or false on error
+	 * @throws MWException
+	 */
+	public static function insertToForeignDefault( $data, $wiki ) {
+		return self::insertToDefault( $data, array( 'wiki' => $wiki ) );
+	}
+}
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;
+	}
+}
diff --git a/includes/externalstore/ExternalStoreHttp.php b/includes/externalstore/ExternalStoreHttp.php
new file mode 100644
index 00000000..345c17be
--- /dev/null
+++ b/includes/externalstore/ExternalStoreHttp.php
@@ -0,0 +1,43 @@
+<?php
+/**
+ * External storage using HTTP requests.
+ *
+ * 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
+ */
+
+/**
+ * Example class for HTTP accessable external objects.
+ * Only supports reading, not storing.
+ *
+ * @ingroup ExternalStorage
+ */
+class ExternalStoreHttp extends ExternalStoreMedium {
+	/**
+	 * @see ExternalStoreMedium::fetchFromURL()
+	 */
+	public function fetchFromURL( $url ) {
+		return Http::get( $url );
+	}
+
+	/**
+	 * @see ExternalStoreMedium::store()
+	 */
+	public function store( $cluster, $data ) {
+		throw new MWException( "ExternalStoreHttp is read-only and does not support store()." );
+	}
+}
diff --git a/includes/externalstore/ExternalStoreMedium.php b/includes/externalstore/ExternalStoreMedium.php
new file mode 100644
index 00000000..41af7d87
--- /dev/null
+++ b/includes/externalstore/ExternalStoreMedium.php
@@ -0,0 +1,60 @@
+<?php
+/**
+ * External storage in some particular medium.
+ *
+ * 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
+ * @ingroup ExternalStorage
+ * @author Aaron Schulz
+ */
+
+/**
+ * Accessable external objects in a particular storage medium
+ *
+ * @ingroup ExternalStorage
+ * @since 1.21
+ */
+abstract class ExternalStoreMedium {
+	/** @var Array */
+	protected $params = array();
+
+	/**
+	 * @param array $params Options
+	 */
+	public function __construct( array $params = array() ) {
+		$this->params = $params;
+	}
+
+	/**
+	 * Fetch data from given external store URL
+	 *
+	 * @param string $url An external store URL
+	 * @return string|bool The text stored or false on error
+	 * @throws MWException
+	 */
+	abstract public function fetchFromURL( $url );
+
+	/**
+	 * Insert a data item into a given location
+	 *
+	 * @param string $location the location name
+	 * @param string $data the data item
+	 * @return string|bool The URL of the stored data item, or false on error
+	 * @throws MWException
+	 */
+	abstract public function store( $location, $data );
+}
diff --git a/includes/externalstore/ExternalStoreMwstore.php b/includes/externalstore/ExternalStoreMwstore.php
new file mode 100644
index 00000000..0911cca1
--- /dev/null
+++ b/includes/externalstore/ExternalStoreMwstore.php
@@ -0,0 +1,72 @@
+<?php
+/**
+ * External storage in a file backend.
+ *
+ * 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
+ */
+
+/**
+ * File backend accessable external objects.
+ *
+ * In this system, each store "location" maps to the name of a file backend.
+ * The file backends must be defined in $wgFileBackends and must be global
+ * and fully qualified with a global "wikiId" prefix in the configuration.
+ *
+ * @ingroup ExternalStorage
+ * @since 1.21
+ */
+class ExternalStoreMwstore extends ExternalStoreMedium {
+	/**
+	 * The URL returned is of the form of the form mwstore://backend/container/wiki/id
+	 *
+	 * @see ExternalStoreMedium::fetchFromURL()
+	 */
+	public function fetchFromURL( $url ) {
+		$be = FileBackendGroup::singleton()->backendFromPath( $url );
+		if ( $be instanceof FileBackend ) {
+			// We don't need "latest" since objects are immutable and
+			// backends should at least have "read-after-create" consistency.
+			return $be->getFileContents( array( 'src' => $url ) );
+		}
+		return false;
+	}
+
+	/**
+	 * @see ExternalStoreMedium::store()
+	 */
+	public function store( $backend, $data ) {
+		$be = FileBackendGroup::singleton()->get( $backend );
+		if ( $be instanceof FileBackend ) {
+			// Get three random base 36 characters to act as shard directories
+			$rand = wfBaseConvert( mt_rand( 0, 46655 ), 10, 36, 3 );
+			// Make sure ID is roughly lexicographically increasing for performance
+			$id = str_pad( UIDGenerator::newTimestampedUID128( 32 ), 26, '0', STR_PAD_LEFT );
+			// Segregate items by wiki ID for the sake of bookkeeping
+			$wiki = isset( $this->params['wiki'] ) ? $this->params['wiki'] : wfWikiID();
+
+			$url = $be->getContainerStoragePath( 'data' ) . '/' .
+				rawurlencode( $wiki ) . "/{$rand[0]}/{$rand[1]}/{$rand[2]}/{$id}";
+
+			$be->prepare( array( 'dir' => dirname( $url ), 'noAccess' => 1, 'noListing' => 1 ) );
+			if ( $be->create( array( 'dst' => $url, 'content' => $data ) )->isOK() ) {
+				return $url;
+			}
+		}
+		return false;
+	}
+}