From 1171cc00cd533ae9b497feeafe1218ac05453c93 Mon Sep 17 00:00:00 2001
From: Aaron Schulz <aschulz@wikimedia.org>
Date: Fri, 9 Oct 2015 01:01:28 -0700
Subject: [PATCH] Inject MultiWriteBagOStuff addCallableUpdate() dependency

Inject the DeferredUpdates::addCallableUpdate method via the
ObjectCache. This brings it closer to being able to move to /libs.

Change-Id: Ifa0d893002c3d709a4dc7346c263a92162274bd7
---
 includes/objectcache/MultiWriteBagOStuff.php  | 47 ++++++++++++-------
 includes/objectcache/ObjectCache.php          |  3 ++
 .../objectcache/MultiWriteBagOStuffTest.php   |  3 +-
 3 files changed, 34 insertions(+), 19 deletions(-)

diff --git a/includes/objectcache/MultiWriteBagOStuff.php b/includes/objectcache/MultiWriteBagOStuff.php
index a9304c1d9a..50dd215146 100644
--- a/includes/objectcache/MultiWriteBagOStuff.php
+++ b/includes/objectcache/MultiWriteBagOStuff.php
@@ -33,6 +33,8 @@ class MultiWriteBagOStuff extends BagOStuff {
 	protected $caches;
 	/** @var bool Use async secondary writes */
 	protected $asyncWrites = false;
+	/** @var callback|null */
+	protected $asyncHandler;
 
 	/** Idiom for "write to all backends" */
 	const ALL = INF;
@@ -41,22 +43,23 @@ class MultiWriteBagOStuff extends BagOStuff {
 
 	/**
 	 * $params include:
-	 *   - caches:      A numbered array of either ObjectFactory::getObjectFromSpec
-	 *                  arrays yeilding BagOStuff objects or direct BagOStuff objects.
-	 *                  If using the former, the 'args' field *must* be set.
-	 *                  The first cache is the primary one, being the first to
-	 *                  be read in the fallback chain. Writes happen to all stores
-	 *                  in the order they are defined. However, lock()/unlock() calls
-	 *                  only use the primary store.
-	 *   - replication: Either 'sync' or 'async'. This controls whether writes to
-	 *                  secondary stores are deferred when possible. Async writes
-	 *                  require the HHVM register_postsend_function() function.
-	 *                  Async writes can increase the chance of some race conditions
-	 *                  or cause keys to expire seconds later than expected. It is
-	 *                  safe to use for modules when cached values: are immutable,
-	 *                  invalidation uses logical TTLs, invalidation uses etag/timestamp
-	 *                  validation against the DB, or merge() is used to handle races.
-	 *
+	 *   - caches: A numbered array of either ObjectFactory::getObjectFromSpec
+	 *      arrays yeilding BagOStuff objects or direct BagOStuff objects.
+	 *      If using the former, the 'args' field *must* be set.
+	 *      The first cache is the primary one, being the first to
+	 *      be read in the fallback chain. Writes happen to all stores
+	 *      in the order they are defined. However, lock()/unlock() calls
+	 *      only use the primary store.
+	 *   - replication: Either 'sync' or 'async'. This controls whether writes
+	 *      to secondary stores are deferred when possible. Async writes
+	 *      require setting 'asyncCallback'. HHVM register_postsend_function() function.
+	 *      Async writes can increase the chance of some race conditions
+	 *      or cause keys to expire seconds later than expected. It is
+	 *      safe to use for modules when cached values: are immutable,
+	 *      invalidation uses logical TTLs, invalidation uses etag/timestamp
+	 *      validation against the DB, or merge() is used to handle races.
+	 *   - asyncHandler: callable that takes a callback and runs it after the
+	 *      current web request ends. In CLI mode, it should run it immediately.
 	 * @param array $params
 	 * @throws InvalidArgumentException
 	 */
@@ -85,7 +88,14 @@ class MultiWriteBagOStuff extends BagOStuff {
 			}
 		}
 
-		$this->asyncWrites = isset( $params['replication'] ) && $params['replication'] === 'async';
+		$this->asyncHandler = isset( $params['asyncHandler'] )
+			? $params['asyncHandler']
+			: null;
+		$this->asyncWrites = (
+			isset( $params['replication'] ) &&
+			$params['replication'] === 'async' &&
+			is_callable( $this->asyncHandler )
+		);
 	}
 
 	/**
@@ -226,7 +236,8 @@ class MultiWriteBagOStuff extends BagOStuff {
 			} else {
 				// Secondary write in async mode: do not block this HTTP request
 				$logger = $this->logger;
-				DeferredUpdates::addCallableUpdate(
+				call_user_func(
+					$this->asyncHandler,
 					function () use ( $cache, $method, $args, $logger ) {
 						if ( !call_user_func_array( array( $cache, $method ), $args ) ) {
 							$logger->warning( "Async $method op failed" );
diff --git a/includes/objectcache/ObjectCache.php b/includes/objectcache/ObjectCache.php
index 3665c11681..151bb065f9 100644
--- a/includes/objectcache/ObjectCache.php
+++ b/includes/objectcache/ObjectCache.php
@@ -178,6 +178,9 @@ class ObjectCache {
 			return call_user_func( $params['factory'], $params );
 		} elseif ( isset( $params['class'] ) ) {
 			$class = $params['class'];
+			if ( $class === 'MultiWriteBagOStuff' && !isset( $params['asyncHandler'] ) ) {
+				$params['asyncHandler'] = 'DeferredUpdates::addCallableUpdate';
+			}
 			return new $class( $params );
 		} else {
 			throw new MWException( "The definition of cache type \""
diff --git a/tests/phpunit/includes/objectcache/MultiWriteBagOStuffTest.php b/tests/phpunit/includes/objectcache/MultiWriteBagOStuffTest.php
index 2b66181c9f..ac52e1256f 100644
--- a/tests/phpunit/includes/objectcache/MultiWriteBagOStuffTest.php
+++ b/tests/phpunit/includes/objectcache/MultiWriteBagOStuffTest.php
@@ -18,7 +18,8 @@ class MultiWriteBagOStuffTest extends MediaWikiTestCase {
 		$this->cache2 = new HashBagOStuff();
 		$this->cache = new MultiWriteBagOStuff( array(
 			'caches' => array( $this->cache1, $this->cache2 ),
-			'replication' => 'async'
+			'replication' => 'async',
+			'asyncHandler' => 'DeferredUpdates::addCallableUpdate'
 		) );
 	}
 
-- 
2.20.1