From 5090f78e11ea671769de69da02fe05ac6540a762 Mon Sep 17 00:00:00 2001
From: Aaron Schulz <aschulz@wikimedia.org>
Date: Sat, 2 Mar 2013 20:41:38 -0800
Subject: [PATCH] [JobQueue] Cleaned up handling of orders a bit.

Change-Id: I83d060e0db97d5bebf042041b0bd20563b093418
---
 includes/job/JobQueue.php      | 34 +++++++++++++++++++++++++++++-----
 includes/job/JobQueueDB.php    |  8 ++++++++
 includes/job/JobQueueRedis.php |  8 ++++++++
 3 files changed, 45 insertions(+), 5 deletions(-)

diff --git a/includes/job/JobQueue.php b/includes/job/JobQueue.php
index 8ade0d564a..641a61de98 100644
--- a/includes/job/JobQueue.php
+++ b/includes/job/JobQueue.php
@@ -43,9 +43,16 @@ abstract class JobQueue {
 	protected function __construct( array $params ) {
 		$this->wiki = $params['wiki'];
 		$this->type = $params['type'];
-		$this->order = isset( $params['order'] ) ? $params['order'] : 'random';
 		$this->claimTTL = isset( $params['claimTTL'] ) ? $params['claimTTL'] : 0;
 		$this->maxTries = isset( $params['maxTries'] ) ? $params['maxTries'] : 3;
+		if ( isset( $params['order'] ) && $params['order'] !== 'any' ) {
+			$this->order = $params['order'];
+		} else {
+			$this->order = $this->optimalOrder();
+		}
+		if ( !in_array( $this->order, $this->supportedOrders() ) ) {
+			throw new MWException( __CLASS__ . " does not support '{$this->order}' order." );
+		}
 	}
 
 	/**
@@ -60,10 +67,10 @@ abstract class JobQueue {
 	 *                job runners since jobs can take different times to finish once popped.
 	 *                If "timestamp" is used, the queue will at least be loosely ordered
 	 *                by timestamp, allowing for some jobs to be popped off out of order.
-	 *                If "random" is used, pop() will pick jobs in random order. This might be
-	 *                useful for improving concurrency depending on the queue storage medium.
-	 *                Note that "random" really means "don't care", so it may actually be FIFO
-	 *                or only weakly random (e.g. pop() takes one of the first X jobs randomly).
+	 *                If "random" is used, pop() will pick jobs in random order.
+	 *                Note that it may only be weakly random (e.g. a lottery of the oldest X).
+	 *                If "any" is choosen, the queue will use whatever order is the fastest.
+	 *                This might be useful for improving concurrency for job acquisition.
 	 *   - claimTTL : If supported, the queue will recycle jobs that have been popped
 	 *                but not acknowledged as completed after this many seconds. Recycling
 	 *                of jobs simple means re-inserting them into the queue. Jobs can be
@@ -101,6 +108,23 @@ abstract class JobQueue {
 		return $this->type;
 	}
 
+	/**
+	 * @return string One of (random, timestamp, fifo)
+	 */
+	final public function getOrder() {
+		return $this->order;
+	}
+
+	/**
+	 * @return Array Subset of (random, timestamp, fifo)
+	 */
+	abstract public function supportedOrders();
+
+	/**
+	 * @return string One of (random, timestamp, fifo)
+	 */
+	abstract protected function optimalOrder();
+
 	/**
 	 * Quickly check if the queue is empty (has no available jobs).
 	 * Queue classes should use caching if they are any slower without memcached.
diff --git a/includes/job/JobQueueDB.php b/includes/job/JobQueueDB.php
index ada0ac4a40..eb01c3e9a8 100644
--- a/includes/job/JobQueueDB.php
+++ b/includes/job/JobQueueDB.php
@@ -50,6 +50,14 @@ class JobQueueDB extends JobQueue {
 		$this->cluster = isset( $params['cluster'] ) ? $params['cluster'] : false;
 	}
 
+	public function supportedOrders() {
+		return array( 'random', 'timestamp', 'fifo' );
+	}
+
+	protected function optimalOrder() {
+		return 'random';
+	}
+
 	/**
 	 * @see JobQueue::doIsEmpty()
 	 * @return bool
diff --git a/includes/job/JobQueueRedis.php b/includes/job/JobQueueRedis.php
index 7dc9900dba..8e7588ec26 100644
--- a/includes/job/JobQueueRedis.php
+++ b/includes/job/JobQueueRedis.php
@@ -52,6 +52,14 @@ class JobQueueRedis extends JobQueue {
 		$this->redisPool = RedisConnectionPool::singleton( $params['redisConfig'] );
 	}
 
+	public function supportedOrders() {
+		return array( 'timestamp', 'fifo' );
+	}
+
+	protected function optimalOrder() {
+		return 'fifo';
+	}
+
 	/**
 	 * @see JobQueue::doIsEmpty()
 	 * @return bool
-- 
2.20.1