From 6b2f8639b681bdaec318d5423a202e46ea796846 Mon Sep 17 00:00:00 2001
From: Timo Tijhof <krinklemail@gmail.com>
Date: Thu, 12 Oct 2017 21:19:56 +0100
Subject: [PATCH] deferred: Introduce TransactionRoundDefiningUpdate

This allows scheduling of updates that need to start their own
transaction round. Specifically for cases where the ability to
commit early is not enough (which is already possible via LBFactory
getEmptyTransactionTicket and commitAndWaitForReplication).

Change-Id: I0910587b61c8ddf825f91e92c2f93582cc7ebd80
---
 autoload.php                                  |  1 +
 includes/deferred/DeferredUpdates.php         |  2 +
 .../TransactionRoundDefiningUpdate.php        | 31 +++++++++++++
 .../includes/deferred/DeferredUpdatesTest.php | 44 +++++++++++++++++++
 .../TransactionRoundDefiningUpdateTest.php    | 17 +++++++
 5 files changed, 95 insertions(+)
 create mode 100644 includes/deferred/TransactionRoundDefiningUpdate.php
 create mode 100644 tests/phpunit/includes/deferred/TransactionRoundDefiningUpdateTest.php

diff --git a/autoload.php b/autoload.php
index 0a2ecf01c5..ede520f9dc 100644
--- a/autoload.php
+++ b/autoload.php
@@ -1498,6 +1498,7 @@ $wgAutoloadLocalClasses = [
 	'TrackBlobs' => __DIR__ . '/maintenance/storage/trackBlobs.php',
 	'TrackingCategories' => __DIR__ . '/includes/TrackingCategories.php',
 	'TraditionalImageGallery' => __DIR__ . '/includes/gallery/TraditionalImageGallery.php',
+	'TransactionRoundDefiningUpdate' => __DIR__ . '/includes/deferred/TransactionRoundDefiningUpdate.php',
 	'TransformParameterError' => __DIR__ . '/includes/media/MediaTransformOutput.php',
 	'TransformTooBigImageAreaError' => __DIR__ . '/includes/media/MediaTransformOutput.php',
 	'TransformationalImageHandler' => __DIR__ . '/includes/media/TransformationalImageHandler.php',
diff --git a/includes/deferred/DeferredUpdates.php b/includes/deferred/DeferredUpdates.php
index e8e250b551..3c4833c7f0 100644
--- a/includes/deferred/DeferredUpdates.php
+++ b/includes/deferred/DeferredUpdates.php
@@ -250,6 +250,8 @@ class DeferredUpdates {
 				// Run only the job enqueue logic to complete the update later
 				$spec = $update->getAsJobSpecification();
 				JobQueueGroup::singleton( $spec['wiki'] )->push( $spec['job'] );
+			} elseif ( $update instanceof TransactionRoundDefiningUpdate ) {
+				$update->doUpdate();
 			} else {
 				// Run the bulk of the update now
 				$fnameTrxOwner = get_class( $update ) . '::doUpdate';
diff --git a/includes/deferred/TransactionRoundDefiningUpdate.php b/includes/deferred/TransactionRoundDefiningUpdate.php
new file mode 100644
index 0000000000..65baec5d51
--- /dev/null
+++ b/includes/deferred/TransactionRoundDefiningUpdate.php
@@ -0,0 +1,31 @@
+<?php
+
+/**
+ * Deferrable update for closure/callback updates that need LBFactory and Database
+ * to be outside any active transaction round.
+ *
+ * @since 1.31
+ */
+class TransactionRoundDefiningUpdate implements DeferrableUpdate, DeferrableCallback {
+	/** @var callable|null */
+	private $callback;
+	/** @var string */
+	private $fname;
+
+	/**
+	 * @param callable $callback
+	 * @param string $fname Calling method
+	 */
+	public function __construct( callable $callback, $fname = 'unknown' ) {
+		$this->callback = $callback;
+		$this->fname = $fname;
+	}
+
+	public function doUpdate() {
+		call_user_func( $this->callback );
+	}
+
+	public function getOrigin() {
+		return $this->fname;
+	}
+}
diff --git a/tests/phpunit/includes/deferred/DeferredUpdatesTest.php b/tests/phpunit/includes/deferred/DeferredUpdatesTest.php
index 999ad03935..8332d2ccc2 100644
--- a/tests/phpunit/includes/deferred/DeferredUpdatesTest.php
+++ b/tests/phpunit/includes/deferred/DeferredUpdatesTest.php
@@ -1,5 +1,7 @@
 <?php
 
+use MediaWiki\MediaWikiServices;
+
 class DeferredUpdatesTest extends MediaWikiTestCase {
 
 	/**
@@ -289,4 +291,46 @@ class DeferredUpdatesTest extends MediaWikiTestCase {
 		$this->assertTrue( $x, "Outer POSTSEND update ran" );
 		$this->assertTrue( $y, "Nested PRESEND update ran" );
 	}
+
+	/**
+	 * @covers DeferredUpdates::runUpdate
+	 */
+	public function testRunUpdateTransactionScope() {
+		$this->setMwGlobals( 'wgCommandLineMode', false );
+
+		$lbFactory = MediaWikiServices::getInstance()->getDBLoadBalancerFactory();
+		$this->assertFalse( $lbFactory->hasTransactionRound(), 'Initial state' );
+
+		$ran = 0;
+		DeferredUpdates::addCallableUpdate( function () use ( &$ran, $lbFactory ) {
+			$ran++;
+			$this->assertTrue( $lbFactory->hasTransactionRound(), 'Has transaction' );
+		} );
+		DeferredUpdates::doUpdates();
+
+		$this->assertSame( 1, $ran, 'Update ran' );
+		$this->assertFalse( $lbFactory->hasTransactionRound(), 'Final state' );
+	}
+
+	/**
+	 * @covers DeferredUpdates::runUpdate
+	 * @covers TransactionRoundDefiningUpdate::getOrigin
+	 */
+	public function testRunOuterScopeUpdate() {
+		$this->setMwGlobals( 'wgCommandLineMode', false );
+
+		$lbFactory = MediaWikiServices::getInstance()->getDBLoadBalancerFactory();
+		$this->assertFalse( $lbFactory->hasTransactionRound(), 'Initial state' );
+
+		$ran = 0;
+		DeferredUpdates::addUpdate( new TransactionRoundDefiningUpdate(
+			function () use ( &$ran, $lbFactory ) {
+				$ran++;
+				$this->assertFalse( $lbFactory->hasTransactionRound(), 'No transaction' );
+			} )
+		);
+		DeferredUpdates::doUpdates();
+
+		$this->assertSame( 1, $ran, 'Update ran' );
+	}
 }
diff --git a/tests/phpunit/includes/deferred/TransactionRoundDefiningUpdateTest.php b/tests/phpunit/includes/deferred/TransactionRoundDefiningUpdateTest.php
new file mode 100644
index 0000000000..e6ad072516
--- /dev/null
+++ b/tests/phpunit/includes/deferred/TransactionRoundDefiningUpdateTest.php
@@ -0,0 +1,17 @@
+<?php
+
+/**
+ * @covers TransactionRoundDefiningUpdate
+ */
+class TransactionRoundDefiningUpdateTest extends PHPUnit_Framework_TestCase {
+
+	public function testDoUpdate() {
+		$ran = 0;
+		$update = new TransactionRoundDefiningUpdate( function () use ( &$ran ) {
+			$ran++;
+		} );
+		$this->assertSame( 0, $ran );
+		$update->doUpdate();
+		$this->assertSame( 1, $ran );
+	}
+}
-- 
2.20.1