From 0a13e6557d524ca951e71eea1cbcb6271c0a413f Mon Sep 17 00:00:00 2001
From: Aaron Schulz <aschulz@wikimedia.org>
Date: Fri, 23 Sep 2016 23:03:56 -0700
Subject: [PATCH] Set ignore_user_abort( true ) during DB commit for sanity

MediaWiki already does this in preOutputCommit(), but it should
also be in the DB layer.

Change-Id: I3193c236a7823f27938077b372887867aeaf78c5
---
 .../ChronologyProtector.php                   |  2 +-
 includes/libs/rdbms/lbfactory/ILBFactory.php  |  6 +++---
 includes/libs/rdbms/lbfactory/LBFactory.php   | 19 ++++++++++++++++++
 .../libs/rdbms/loadbalancer/LoadBalancer.php  | 20 +++++++++++++++++++
 4 files changed, 43 insertions(+), 4 deletions(-)

diff --git a/includes/libs/rdbms/chronologyprotector/ChronologyProtector.php b/includes/libs/rdbms/chronologyprotector/ChronologyProtector.php
index 94a3b6ce1e..1f9aff161e 100644
--- a/includes/libs/rdbms/chronologyprotector/ChronologyProtector.php
+++ b/includes/libs/rdbms/chronologyprotector/ChronologyProtector.php
@@ -27,7 +27,7 @@ use Psr\Log\LoggerInterface;
  * Class for ensuring a consistent ordering of events as seen by the user, despite replication.
  * Kind of like Hawking's [[Chronology Protection Agency]].
  */
-class ChronologyProtector implements LoggerAwareInterface{
+class ChronologyProtector implements LoggerAwareInterface {
 	/** @var BagOStuff */
 	protected $store;
 	/** @var LoggerInterface */
diff --git a/includes/libs/rdbms/lbfactory/ILBFactory.php b/includes/libs/rdbms/lbfactory/ILBFactory.php
index d7ca7cd1a9..9c9f18d2b0 100644
--- a/includes/libs/rdbms/lbfactory/ILBFactory.php
+++ b/includes/libs/rdbms/lbfactory/ILBFactory.php
@@ -136,9 +136,9 @@ interface ILBFactory {
 	public function flushReplicaSnapshots( $fname = __METHOD__ );
 
 	/**
-	 * Commit on all connections. Done for two reasons:
-	 * 1. To commit changes to the masters.
-	 * 2. To release the snapshot on all connections, master and replica DB.
+	 * Commit open transactions on all connections. This is useful for two main cases:
+	 *   - a) To commit changes to the masters.
+	 *   - b) To release the snapshot on all connections, master and replica DBs.
 	 * @param string $fname Caller name
 	 * @param array $options Options map:
 	 *   - maxWriteDuration: abort if more than this much time was spent in write queries
diff --git a/includes/libs/rdbms/lbfactory/LBFactory.php b/includes/libs/rdbms/lbfactory/LBFactory.php
index 85194bc009..0635d04c7b 100644
--- a/includes/libs/rdbms/lbfactory/LBFactory.php
+++ b/includes/libs/rdbms/lbfactory/LBFactory.php
@@ -178,6 +178,8 @@ abstract class LBFactory implements ILBFactory {
 				"$fname: transaction round '{$this->trxRoundId}' still running."
 			);
 		}
+		/** @noinspection PhpUnusedLocalVariableInspection */
+		$scope = $this->getScopedPHPBehaviorForCommit(); // try to ignore client aborts
 		// Run pre-commit callbacks and suppress post-commit callbacks, aborting on failure
 		$this->forEachLBCallMethod( 'finalizeMasterChanges' );
 		$this->trxRoundId = false;
@@ -516,6 +518,23 @@ abstract class LBFactory implements ILBFactory {
 		$this->requestInfo = $info + $this->requestInfo;
 	}
 
+	/**
+	 * Make PHP ignore user aborts/disconnects until the returned
+	 * value leaves scope. This returns null and does nothing in CLI mode.
+	 *
+	 * @return ScopedCallback|null
+	 */
+	final protected function getScopedPHPBehaviorForCommit() {
+		if ( PHP_SAPI != 'cli' ) { // http://bugs.php.net/bug.php?id=47540
+			$old = ignore_user_abort( true ); // avoid half-finished operations
+			return new ScopedCallback( function () use ( $old ) {
+				ignore_user_abort( $old );
+			} );
+		}
+
+		return null;
+	}
+
 	function __destruct() {
 		$this->destroy();
 	}
diff --git a/includes/libs/rdbms/loadbalancer/LoadBalancer.php b/includes/libs/rdbms/loadbalancer/LoadBalancer.php
index 36e4c6c662..7ad275a96c 100644
--- a/includes/libs/rdbms/loadbalancer/LoadBalancer.php
+++ b/includes/libs/rdbms/loadbalancer/LoadBalancer.php
@@ -1101,6 +1101,9 @@ class LoadBalancer implements ILoadBalancer {
 	public function commitMasterChanges( $fname = __METHOD__ ) {
 		$failures = [];
 
+		/** @noinspection PhpUnusedLocalVariableInspection */
+		$scope = $this->getScopedPHPBehaviorForCommit(); // try to ignore client aborts
+
 		$restore = ( $this->trxRoundId !== false );
 		$this->trxRoundId = false;
 		$this->forEachOpenMasterConnection(
@@ -1516,6 +1519,23 @@ class LoadBalancer implements ILoadBalancer {
 		} );
 	}
 
+	/**
+	 * Make PHP ignore user aborts/disconnects until the returned
+	 * value leaves scope. This returns null and does nothing in CLI mode.
+	 *
+	 * @return ScopedCallback|null
+	 */
+	final protected function getScopedPHPBehaviorForCommit() {
+		if ( PHP_SAPI != 'cli' ) { // http://bugs.php.net/bug.php?id=47540
+			$old = ignore_user_abort( true ); // avoid half-finished operations
+			return new ScopedCallback( function () use ( $old ) {
+				ignore_user_abort( $old );
+			} );
+		}
+
+		return null;
+	}
+
 	function __destruct() {
 		// Avoid connection leaks for sanity
 		$this->closeAll();
-- 
2.20.1