From 25a44aa3e4fa511d326b373af71762eb7375db7a Mon Sep 17 00:00:00 2001
From: Aaron Schulz <aschulz@wikimedia.org>
Date: Tue, 22 Sep 2015 11:43:33 -0700
Subject: [PATCH] Added support for enqueueable DataUpdates

* Updates can now declare themselves as having enqueueUpdate()
  as an alternative to doUpdate(). This lets more expensive
  or slave lag producing updates use the job queue if desired.
* Added a $mode flag to DataUpdate::runUpdates() to prefer
  pushing jobs over calling doUpdate().
* Made page deletions defer deletion updates when possible.

Bug: T95501
Change-Id: Ic6f50f92768089ba0fbc223b8d178f5a91512959
---
 autoload.php                     |  1 +
 includes/deferred/DataUpdate.php | 56 ++++++++++++++++++++++++--------
 includes/page/WikiPage.php       |  2 +-
 3 files changed, 45 insertions(+), 14 deletions(-)

diff --git a/autoload.php b/autoload.php
index 4bed0141bf..0c0324371a 100644
--- a/autoload.php
+++ b/autoload.php
@@ -384,6 +384,7 @@ $wgAutoloadLocalClasses = array(
 	'EnhancedChangesList' => __DIR__ . '/includes/changes/EnhancedChangesList.php',
 	'EnotifNotifyJob' => __DIR__ . '/includes/jobqueue/jobs/EnotifNotifyJob.php',
 	'EnqueueJob' => __DIR__ . '/includes/jobqueue/jobs/EnqueueJob.php',
+	'EnqueueableDataUpdate' => __DIR__ . '/includes/deferred/DataUpdate.php',
 	'EraseArchivedFile' => __DIR__ . '/maintenance/eraseArchivedFile.php',
 	'ErrorPageError' => __DIR__ . '/includes/exception/ErrorPageError.php',
 	'EventRelayer' => __DIR__ . '/includes/libs/eventrelayer/EventRelayer.php',
diff --git a/includes/deferred/DataUpdate.php b/includes/deferred/DataUpdate.php
index ed12c6012e..f5d6845deb 100644
--- a/includes/deferred/DataUpdate.php
+++ b/includes/deferred/DataUpdate.php
@@ -30,11 +30,8 @@
  *       subclasses can override the beginTransaction() and commitTransaction() methods.
  */
 abstract class DataUpdate implements DeferrableUpdate {
-	/**
-	 * Constructor
-	 */
 	public function __construct() {
-		# noop
+		//noop
 	}
 
 	/**
@@ -73,22 +70,23 @@ abstract class DataUpdate implements DeferrableUpdate {
 	 * This allows for limited transactional logic across multiple backends for storing
 	 * secondary data.
 	 *
-	 * @param array $updates A list of DataUpdate instances
+	 * @param DataUpdate[] $updates A list of DataUpdate instances
+	 * @param string $mode Use "enqueue" to use the job queue when possible [Default: run]
 	 * @throws Exception|null
 	 */
-	public static function runUpdates( $updates ) {
-		if ( empty( $updates ) ) {
-			return; # nothing to do
+	public static function runUpdates( array $updates, $mode = 'run' ) {
+		if ( $mode === 'enqueue' ) {
+			// When possible, push updates as jobs instead of calling doUpdate()
+			$updates = self::enqueueUpdates( $updates );
+		}
+
+		if ( !count( $updates ) ) {
+			return; // nothing to do
 		}
 
 		$open_transactions = array();
 		$exception = null;
 
-		/**
-		 * @var $update DataUpdate
-		 * @var $trans DataUpdate
-		 */
-
 		try {
 			// begin transactions
 			foreach ( $updates as $update ) {
@@ -122,4 +120,36 @@ abstract class DataUpdate implements DeferrableUpdate {
 			throw $exception; // rethrow after cleanup
 		}
 	}
+
+	/**
+	 * Enqueue jobs for every DataUpdate that support enqueueUpdate()
+	 * and return the remaining DataUpdate objects (those that do not)
+	 *
+	 * @param DataUpdate[] $updates A list of DataUpdate instances
+	 * @return DataUpdate[]
+	 * @since 1.26
+	 */
+	protected static function enqueueUpdates( array $updates ) {
+		$remaining = array();
+
+		foreach ( $updates as $update ) {
+			if ( $update instanceof EnqueueableDataUpdate ) {
+				$update->enqueueUpdate();
+			} else {
+				$remaining[] = $update;
+			}
+		}
+
+		return $remaining;
+	}
 }
+
+/**
+ * @since 1.26
+ */
+interface EnqueueableDataUpdate {
+	/**
+	 * Push the update into the job queue
+	 */
+	public function enqueueUpdate();
+}
\ No newline at end of file
diff --git a/includes/page/WikiPage.php b/includes/page/WikiPage.php
index d1cec60b9a..c99928a1c7 100644
--- a/includes/page/WikiPage.php
+++ b/includes/page/WikiPage.php
@@ -2916,7 +2916,7 @@ class WikiPage implements Page, IDBAccessObject {
 
 		// remove secondary indexes, etc
 		$updates = $this->getDeletionUpdates( $content );
-		DataUpdate::runUpdates( $updates );
+		DataUpdate::runUpdates( $updates, 'enqueue' );
 
 		// Reparse any pages transcluding this page
 		LinksUpdate::queueRecursiveJobsForTable( $this->mTitle, 'templatelinks' );
-- 
2.20.1