1 files changed, 124 insertions, 0 deletions
diff --git a/includes/DataUpdate.php b/includes/DataUpdate.php
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+<?php
+/**
+ * Base code for update jobs that do something with some secondary
+ * data extracted from article.
+ *
+ * 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
+ */
+
+/**
+ * Abstract base class for update jobs that do something with some secondary
+ * data extracted from article.
+ *
+ * @note: subclasses should NOT start or commit transactions in their doUpdate() method,
+ *        a transaction will automatically be wrapped around the update. If need be,
+ *        subclasses can override the beginTransaction() and commitTransaction() methods.
+ */
+abstract class DataUpdate implements DeferrableUpdate {
+
+	/**
+	 * Constructor
+	 */
+	public function __construct( ) {
+		# noop
+	}
+
+	/**
+	 * Begin an appropriate transaction, if any.
+	 * This default implementation does nothing.
+	 */
+	public function beginTransaction() {
+		//noop
+	}
+
+	/**
+	 * Commit the transaction started via beginTransaction, if any.
+	 * This default implementation does nothing.
+	 */
+	public function commitTransaction() {
+		//noop
+	}
+
+	/**
+	 * Abort / roll back the transaction started via beginTransaction, if any.
+	 * This default implementation does nothing.
+	 */
+	public function rollbackTransaction() {
+		//noop
+	}
+
+	/**
+	 * Convenience method, calls doUpdate() on every DataUpdate in the array.
+	 *
+	 * This methods supports transactions logic by first calling beginTransaction()
+	 * on all updates in the array, then calling doUpdate() on each, and, if all goes well,
+	 * then calling commitTransaction() on each update. If an error occurrs,
+	 * rollbackTransaction() will be called on any update object that had beginTranscation()
+	 * called but not yet commitTransaction().
+	 *
+	 * This allows for limited transactional logic across multiple backends for storing
+	 * secondary data.
+	 *
+	 * @static
+	 * @param $updates array a list of DataUpdate instances
+	 */
+	public static function runUpdates( $updates ) {
+		if ( empty( $updates ) ) return; # nothing to do
+
+		$open_transactions = array();
+		$exception = null;
+
+		/**
+		 * @var $update DataUpdate
+		 * @var $trans DataUpdate
+		 */
+
+		try {
+			// begin transactions
+			foreach ( $updates as $update ) {
+				$update->beginTransaction();
+				$open_transactions[] = $update;
+			}
+
+			// do work
+			foreach ( $updates as $update ) {
+				$update->doUpdate();
+			}
+
+			// commit transactions
+			while ( count( $open_transactions ) > 0 ) {
+				$trans = array_pop( $open_transactions );
+				$trans->commitTransaction();
+			}
+		} catch ( Exception $ex ) {
+			$exception = $ex;
+			wfDebug( "Caught exception, will rethrow after rollback: " . $ex->getMessage() );
+		}
+
+		// rollback remaining transactions
+		while ( count( $open_transactions ) > 0 ) {
+			$trans = array_pop( $open_transactions );
+			$trans->rollbackTransaction();
+		}
+
+		if ( $exception ) {
+			throw $exception; // rethrow after cleanup
+		}
+	}
+
+}