From dbf7e393fb1a348a6a2d2e41dcf0e0da347aaa84 Mon Sep 17 00:00:00 2001
From: Aaron Schulz <aschulz@wikimedia.org>
Date: Wed, 7 Oct 2015 20:44:54 -0700
Subject: [PATCH] Provide a default "max lag" value for LoadBalancer

* No MediaWiki site can tolerate unbounded slave lag
  without editing and account creation and such being
  broken and unusable
* Also fix a few trivial __construct() IDEA errors

Change-Id: I95b8b73be2df3b5a87e7adbf53988cfbeb85c260
---
 includes/db/loadbalancer/LBFactory.php       | 13 +++++++------
 includes/db/loadbalancer/LBFactoryMulti.php  |  2 ++
 includes/db/loadbalancer/LBFactorySimple.php |  2 ++
 includes/db/loadbalancer/LoadBalancer.php    |  4 +++-
 4 files changed, 14 insertions(+), 7 deletions(-)

diff --git a/includes/db/loadbalancer/LBFactory.php b/includes/db/loadbalancer/LBFactory.php
index a06d826e2c..bad04f9c1f 100644
--- a/includes/db/loadbalancer/LBFactory.php
+++ b/includes/db/loadbalancer/LBFactory.php
@@ -29,6 +29,13 @@ abstract class LBFactory {
 	/** @var LBFactory */
 	private static $instance;
 
+	/**
+	 * Construct a factory based on a configuration array (typically from $wgLBFactoryConf)
+	 * @param array $conf
+	 */
+	public function __construct( array $conf ) {
+	}
+
 	/**
 	 * Disables all access to the load balancer, will cause all database access
 	 * to throw a DBAccessError
@@ -105,12 +112,6 @@ abstract class LBFactory {
 		self::$instance = $instance;
 	}
 
-	/**
-	 * Construct a factory based on a configuration array (typically from $wgLBFactoryConf)
-	 * @param array $conf
-	 */
-	abstract public function __construct( array $conf );
-
 	/**
 	 * Create a new load balancer object. The resulting object will be untracked,
 	 * not chronology-protected, and the caller is responsible for cleaning it up.
diff --git a/includes/db/loadbalancer/LBFactoryMulti.php b/includes/db/loadbalancer/LBFactoryMulti.php
index 6397bcaaf0..2655659b77 100644
--- a/includes/db/loadbalancer/LBFactoryMulti.php
+++ b/includes/db/loadbalancer/LBFactoryMulti.php
@@ -158,6 +158,8 @@ class LBFactoryMulti extends LBFactory {
 	 * @throws MWException
 	 */
 	public function __construct( array $conf ) {
+		parent::__construct( $conf );
+
 		$this->chronProt = new ChronologyProtector;
 		$this->conf = $conf;
 		$required = array( 'sectionsByDB', 'sectionLoads', 'serverTemplate' );
diff --git a/includes/db/loadbalancer/LBFactorySimple.php b/includes/db/loadbalancer/LBFactorySimple.php
index 90c33b0c08..e328727daf 100644
--- a/includes/db/loadbalancer/LBFactorySimple.php
+++ b/includes/db/loadbalancer/LBFactorySimple.php
@@ -36,6 +36,8 @@ class LBFactorySimple extends LBFactory {
 	private $loadMonitorClass;
 
 	public function __construct( array $conf ) {
+		parent::__construct( $conf );
+
 		$this->chronProt = new ChronologyProtector;
 		$this->loadMonitorClass = isset( $conf['loadMonitorClass'] )
 			? $conf['loadMonitorClass']
diff --git a/includes/db/loadbalancer/LoadBalancer.php b/includes/db/loadbalancer/LoadBalancer.php
index 3350d19ee5..fbc8c8cdd3 100644
--- a/includes/db/loadbalancer/LoadBalancer.php
+++ b/includes/db/loadbalancer/LoadBalancer.php
@@ -63,6 +63,8 @@ class LoadBalancer {
 
 	/** @var integer Warn when this many connection are held */
 	const CONN_HELD_WARN_THRESHOLD = 10;
+	/** @var integer Default 'max lag' when unspecified */
+	const MAX_LAG = 30;
 
 	/**
 	 * @param array $params Array with keys:
@@ -155,7 +157,7 @@ class LoadBalancer {
 	 * @param float $maxLag Restrict the maximum allowed lag to this many seconds
 	 * @return bool|int|string
 	 */
-	private function getRandomNonLagged( array $loads, $wiki = false, $maxLag = INF ) {
+	private function getRandomNonLagged( array $loads, $wiki = false, $maxLag = self::MAX_LAG ) {
 		$lags = $this->getLagTimes( $wiki );
 
 		# Unset excessively lagged servers
-- 
2.20.1