From 7643d7d885e4d7b6d8b02b81af48abae8c727003 Mon Sep 17 00:00:00 2001
From: Aaron Schulz <aschulz@wikimedia.org>
Date: Tue, 15 Dec 2015 21:34:52 -0800
Subject: [PATCH] Avoid "Incorrect user-level lock name " errors in Database
 lock() method

Use a sha1 hash if the lock name exceeds the MySQL limit. The class
for Postgres already avoids this problem with number hashes.

Change-Id: If587c672b4ff210ee3b512bbe2910ae247079d3f
---
 includes/db/DatabaseMysqlBase.php | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/includes/db/DatabaseMysqlBase.php b/includes/db/DatabaseMysqlBase.php
index ca568add23..b36de98050 100644
--- a/includes/db/DatabaseMysqlBase.php
+++ b/includes/db/DatabaseMysqlBase.php
@@ -845,7 +845,7 @@ abstract class DatabaseMysqlBase extends Database {
 	 * @since 1.20
 	 */
 	public function lockIsFree( $lockName, $method ) {
-		$lockName = $this->addQuotes( $lockName );
+		$lockName = $this->addQuotes( $this->makeLockName( $lockName ) );
 		$result = $this->query( "SELECT IS_FREE_LOCK($lockName) AS lockstatus", $method );
 		$row = $this->fetchObject( $result );
 
@@ -859,7 +859,7 @@ abstract class DatabaseMysqlBase extends Database {
 	 * @return bool
 	 */
 	public function lock( $lockName, $method, $timeout = 5 ) {
-		$lockName = $this->addQuotes( $lockName );
+		$lockName = $this->addQuotes( $this->makeLockName( $lockName ) );
 		$result = $this->query( "SELECT GET_LOCK($lockName, $timeout) AS lockstatus", $method );
 		$row = $this->fetchObject( $result );
 
@@ -880,13 +880,19 @@ abstract class DatabaseMysqlBase extends Database {
 	 * @return bool
 	 */
 	public function unlock( $lockName, $method ) {
-		$lockName = $this->addQuotes( $lockName );
+		$lockName = $this->addQuotes( $this->makeLockName( $lockName ) );
 		$result = $this->query( "SELECT RELEASE_LOCK($lockName) as lockstatus", $method );
 		$row = $this->fetchObject( $result );
 
 		return ( $row->lockstatus == 1 );
 	}
 
+	private function makeLockName( $lockName ) {
+		// http://dev.mysql.com/doc/refman/5.7/en/miscellaneous-functions.html#function_get-lock
+		// Newer version enforce a 64 char length limit.
+		return ( strlen( $lockName ) > 64 ) ? sha1( $lockName ) : $lockName;
+	}
+
 	public function namedLocksEnqueue() {
 		return true;
 	}
-- 
2.20.1