From 9ae936b197eab3c65103abf55255cd9e918f0a9b Mon Sep 17 00:00:00 2001
From: Aaron Schulz <aschulz@wikimedia.org>
Date: Thu, 14 Sep 2017 10:07:38 +0200
Subject: [PATCH] Prefer that enqueueable post-send updates are run immediately

If the user is not waiting at this point, so there is not much
reason to enqueue a job over just doing the work now. Running
the update now gives more immediate results however.

This has the effect of  making LinksUpdate run post-send for
forward link updates, since the addUpdate() call in WikiPage uses
the default POSTSEND mode. These updates used to be synchronous
in the past, before proper post-send update support. With post-send
updates, there is not much benefit to using the job queue here.

If post-send updates are not supported, this will continue to
use the job queue.

If a caller needs such updates to enqueue post-send to avoid DB
updates on HTTP GET or if the update is too big to run outside of
JobRunner, it can always just use JobQueueGroup::lazyPush() with
a direct job object or JobSpecification.

Change-Id: Ibc4b1e17538cc8b1fba7d13759e1ebb83abed869
---
 includes/MediaWiki.php | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/includes/MediaWiki.php b/includes/MediaWiki.php
index 7b59ee93dc..0f40c19201 100644
--- a/includes/MediaWiki.php
+++ b/includes/MediaWiki.php
@@ -712,10 +712,11 @@ class MediaWiki {
 			MWExceptionHandler::rollbackMasterChangesAndLog( $e );
 		}
 
+		$blocksHttpClient = true;
 		// Defer everything else if possible...
-		$callback = function () use ( $mode ) {
+		$callback = function () use ( $mode, &$blocksHttpClient ) {
 			try {
-				$this->restInPeace( $mode );
+				$this->restInPeace( $mode, $blocksHttpClient );
 			} catch ( Exception $e ) {
 				// If this is post-send, then displaying errors can cause broken HTML
 				MWExceptionHandler::rollbackMasterChangesAndLog( $e );
@@ -725,9 +726,11 @@ class MediaWiki {
 		if ( function_exists( 'register_postsend_function' ) ) {
 			// https://github.com/facebook/hhvm/issues/1230
 			register_postsend_function( $callback );
+			$blocksHttpClient = false;
 		} else {
 			if ( function_exists( 'fastcgi_finish_request' ) ) {
 				fastcgi_finish_request();
+				$blocksHttpClient = false;
 			} else {
 				// Either all DB and deferred updates should happen or none.
 				// The latter should not be cancelled due to client disconnect.
@@ -870,8 +873,9 @@ class MediaWiki {
 	/**
 	 * Ends this task peacefully
 	 * @param string $mode Use 'fast' to always skip job running
+	 * @param bool $blocksHttpClient Whether this blocks an HTTP response to a client
 	 */
-	public function restInPeace( $mode = 'fast' ) {
+	public function restInPeace( $mode = 'fast', $blocksHttpClient = true ) {
 		$lbFactory = MediaWikiServices::getInstance()->getDBLoadBalancerFactory();
 		// Assure deferred updates are not in the main transaction
 		$lbFactory->commitMasterChanges( __METHOD__ );
@@ -887,8 +891,8 @@ class MediaWiki {
 		// Important: this must be the last deferred update added (T100085, T154425)
 		DeferredUpdates::addCallableUpdate( [ JobQueueGroup::class, 'pushLazyJobs' ] );
 
-		// Do any deferred jobs
-		DeferredUpdates::doUpdates( 'enqueue' );
+		// Do any deferred jobs; preferring to run them now if a client will not wait on them
+		DeferredUpdates::doUpdates( $blocksHttpClient ? 'enqueue' : 'run' );
 
 		// Now that everything specific to this request is done,
 		// try to occasionally run jobs (if enabled) from the queues
-- 
2.20.1