From 9c919dd2cfab267c81519426b567ada6f64377dc Mon Sep 17 00:00:00 2001
From: Aaron Schulz <aschulz@wikimedia.org>
Date: Thu, 10 Dec 2015 13:56:11 -0800
Subject: [PATCH] Make edit stashing use named DB locks

These should be faster by avoiding the inefficient back-off
polling in BagOStuff::lock().

Change-Id: I013b2567716eea5e354e13f3e9640573886e596a
---
 includes/api/ApiStashEdit.php | 24 ++++++++++++++++--------
 1 file changed, 16 insertions(+), 8 deletions(-)

diff --git a/includes/api/ApiStashEdit.php b/includes/api/ApiStashEdit.php
index c6d267cc2e..208e9ca880 100644
--- a/includes/api/ApiStashEdit.php
+++ b/includes/api/ApiStashEdit.php
@@ -108,17 +108,17 @@ class ApiStashEdit extends ApiBase {
 		// The user will abort the AJAX request by pressing "save", so ignore that
 		ignore_user_abort( true );
 
+		// Use the master DB for fast blocking locks
+		$dbw = wfGetDB( DB_MASTER );
+
 		// Get a key based on the source text, format, and user preferences
 		$key = self::getStashKey( $title, $content, $user );
 		// De-duplicate requests on the same key
 		if ( $user->pingLimiter( 'stashedit' ) ) {
 			$status = 'ratelimited';
-		} elseif ( $cache->lock( $key, 0, 30 ) ) {
-			/** @noinspection PhpUnusedLocalVariableInspection */
-			$unlocker = new ScopedCallback( function() use ( $cache, $key ) {
-				$cache->unlock( $key );
-			} );
+		} elseif ( $dbw->lock( $key, __METHOD__, 1 ) ) {
 			$status = self::parseAndStash( $page, $content, $user );
+			$dbw->unlock( $key, __METHOD__ );
 		} else {
 			$status = 'busy';
 		}
@@ -258,10 +258,14 @@ class ApiStashEdit extends ApiBase {
 		if ( !is_object( $editInfo ) ) {
 			$start = microtime( true );
 			// We ignore user aborts and keep parsing. Block on any prior parsing
-			// so as to use it's results and make use of the time spent parsing.
-			if ( $cache->lock( $key, 30, 30 ) ) {
+			// so as to use its results and make use of the time spent parsing.
+			// Skip this logic if there no master connection in case this method
+			// is called on an HTTP GET request for some reason.
+			$lb = wfGetLB();
+			$dbw = $lb->getAnyOpenConnection( $lb->getWriterIndex() );
+			if ( $dbw && $dbw->lock( $key, __METHOD__, 30 ) ) {
 				$editInfo = $cache->get( $key );
-				$cache->unlock( $key );
+				$dbw->unlock( $key, __METHOD__ );
 			}
 			$sec = microtime( true ) - $start;
 			if ( $sec > .01 ) {
@@ -430,6 +434,10 @@ class ApiStashEdit extends ApiBase {
 		return true;
 	}
 
+	function isWriteMode() {
+		return true;
+	}
+
 	function isInternal() {
 		return true;
 	}
-- 
2.20.1