From 4c0871fa0ef99d0d38bcba8e09fce8ef55f791d9 Mon Sep 17 00:00:00 2001
From: Aaron Schulz <aschulz@wikimedia.org>
Date: Tue, 15 Jul 2014 19:19:54 -0700
Subject: [PATCH] Made LCStoreDB try to use a separate DB connection

* This avoids breaking the main transaction in finishWrite().
* Also removed an unused variable in SqlBagOStuff.

Change-Id: Ia330ac362b080c1338616d95b793032c4752dc23
---
 includes/cache/LocalisationCache.php  | 15 ++++++++++++---
 includes/objectcache/SqlBagOStuff.php | 15 +++++----------
 2 files changed, 17 insertions(+), 13 deletions(-)

diff --git a/includes/cache/LocalisationCache.php b/includes/cache/LocalisationCache.php
index ec36cfb5ab..9dc3dc3a8e 100644
--- a/includes/cache/LocalisationCache.php
+++ b/includes/cache/LocalisationCache.php
@@ -1163,8 +1163,8 @@ class LCStoreDB implements LCStore {
 	private $readOnly = false;
 
 	public function get( $code, $key ) {
-		if ( $this->writesDone ) {
-			$db = wfGetDB( DB_MASTER );
+		if ( $this->writesDone && $this->dbw ) {
+			$db = $this->dbw;
 		} else {
 			$db = wfGetDB( DB_SLAVE );
 		}
@@ -1184,7 +1184,16 @@ class LCStoreDB implements LCStore {
 			throw new MWException( __METHOD__ . ": Invalid language \"$code\"" );
 		}
 
-		$this->dbw = wfGetDB( DB_MASTER );
+		// We must keep a separate connection to MySQL in order to avoid breaking
+		// main transactions. However, SQLite deadlocks when using two connections.
+		// @TODO: get this trick to work on PostgreSQL too
+		if ( wfGetDB( DB_MASTER )->getType() == 'mysql' ) {
+			$lb = wfGetLBFactory()->newMainLB();
+			$this->dbw = $lb->getConnection( DB_MASTER );
+			$this->dbw->clearFlag( DBO_TRX ); // auto-commit mode
+		} else {
+			$this->dbw = wfGetDB( DB_MASTER );
+		}
 
 		$this->currentLang = $code;
 		$this->batch = array();
diff --git a/includes/objectcache/SqlBagOStuff.php b/includes/objectcache/SqlBagOStuff.php
index 483f8b9ac5..8b0b738cd7 100644
--- a/includes/objectcache/SqlBagOStuff.php
+++ b/includes/objectcache/SqlBagOStuff.php
@@ -27,9 +27,6 @@
  * @ingroup Cache
  */
 class SqlBagOStuff extends BagOStuff {
-	/** @var LoadBalancer */
-	protected $lb;
-
 	protected $serverInfos;
 
 	/** @var array */
@@ -146,14 +143,12 @@ class SqlBagOStuff extends BagOStuff {
 				$db = DatabaseBase::factory( $type, $info );
 				$db->clearFlag( DBO_TRX );
 			} else {
-				/*
-				 * We must keep a separate connection to MySQL in order to avoid deadlocks
-				 * However, SQLite has an opposite behavior. And PostgreSQL needs to know
-				 * if we are in transaction or no
-				 */
+				// We must keep a separate connection to MySQL in order to avoid deadlocks
+				// However, SQLite has an opposite behavior.
+				// @TODO: get this trick to work on PostgreSQL too
 				if ( wfGetDB( DB_MASTER )->getType() == 'mysql' ) {
-					$this->lb = wfGetLBFactory()->newMainLB();
-					$db = $this->lb->getConnection( DB_MASTER );
+					$lb = wfGetLBFactory()->newMainLB();
+					$db = $lb->getConnection( DB_MASTER );
 					$db->clearFlag( DBO_TRX ); // auto-commit mode
 				} else {
 					$db = wfGetDB( DB_MASTER );
-- 
2.20.1