From ebe76658175a7a8c9f190db6747a91f0c91eb988 Mon Sep 17 00:00:00 2001
From: Chris Boulton <chris.boulton@interspire.com>
Date: Mon, 5 Mar 2012 19:21:43 +1100
Subject: [PATCH] fix lost jobs when there is more than one worker process
 started by the same parent process

---
 lib/Resque.php | 61 ++++++++++++++++++++++++++++++++++++++------------
 1 file changed, 47 insertions(+), 14 deletions(-)

diff --git a/lib/Resque.php b/lib/Resque.php
index d0be465..a997356 100644
--- a/lib/Resque.php
+++ b/lib/Resque.php
@@ -19,6 +19,23 @@ class Resque
 	 */
 	public static $redis = null;
 
+	/**
+	 * @var mixed Host/port conbination separated by a colon, or a nested
+	 * array of server swith host/port pairs
+	 */
+	protected static $redisServer = null;
+
+	/**
+	 * @var int ID of Redis database to select.
+	 */
+	protected static $redisDatabase = 0;
+
+	/**
+	 * @var int PID of current process. Used to detect changes when forking
+	 *  and implement "thread" safety to avoid race conditions.
+	 */
+	 protected static $pid = null;
+
 	/**
 	 * Given a host/port combination separated by a colon, set it as
 	 * the redis server that Resque will talk to.
@@ -28,6 +45,35 @@ class Resque
 	 */
 	public static function setBackend($server, $database = 0)
 	{
+		self::$redisServer   = $server;
+		self::$redisDatabase = $database;
+		self::$redis         = null;
+	}
+
+	/**
+	 * Return an instance of the Resque_Redis class instantiated for Resque.
+	 *
+	 * @return Resque_Redis Instance of Resque_Redis.
+	 */
+	public static function redis()
+	{
+		// Detect when the PID of the current process has changed (from a fork, etc)
+		// and force a reconnect to redis.
+		$pid = getmypid();
+		if (self::$pid !== $pid) {
+			self::$redis = null;
+			self::$pid   = $pid;
+		}
+
+		if(!is_null(self::$redis)) {
+			return self::$redis;
+		}
+
+		$server = self::$redisServer;
+		if (empty($server)) {
+			$server = 'localhost:6379';
+		}
+
 		if(is_array($server)) {
 			require_once dirname(__FILE__) . '/Resque/RedisCluster.php';
 			self::$redis = new Resque_RedisCluster($server);
@@ -38,20 +84,7 @@ class Resque
 			self::$redis = new Resque_Redis($host, $port);
 		}
 
-        self::redis()->select($database);
-	}
-
-	/**
-	 * Return an instance of the Resque_Redis class instantiated for Resque.
-	 *
-	 * @return Resque_Redis Instance of Resque_Redis.
-	 */
-	public static function redis()
-	{
-		if(is_null(self::$redis)) {
-			self::setBackend('localhost:6379');
-		}
-
+		self::$redis->select(self::$redisDatabase);
 		return self::$redis;
 	}