1 files changed, 37 insertions, 92 deletions

diff --git a/includes/db/LoadMonitor.php b/includes/db/LoadMonitor.php
index 519e2dfd..7281485b 100644
--- a/includes/db/LoadMonitor.php
+++ b/includes/db/LoadMonitor.php
@@ -32,61 +32,35 @@ interface LoadMonitor {
 	 *
 	 * @param LoadBalancer $parent
 	 */
-	function __construct( $parent );
+	public function __construct( $parent );
 
 	/**
 	 * Perform pre-connection load ratio adjustment.
-	 * @param $loads array
-	 * @param string $group the selected query group
-	 * @param $wiki String
+	 * @param array $loads
+	 * @param string|bool $group The selected query group. Default: false
+	 * @param string|bool $wiki Default: false
 	 */
-	function scaleLoads( &$loads, $group = false, $wiki = false );
-
-	/**
-	 * Perform post-connection backoff.
-	 *
-	 * If the connection is in overload, this should return a backoff factor
-	 * which will be used to control polling time. The number of threads
-	 * connected is a good measure.
-	 *
-	 * If there is no overload, zero can be returned.
-	 *
-	 * A threshold thread count is given, the concrete class may compare this
-	 * to the running thread count. The threshold may be false, which indicates
-	 * that the sysadmin has not configured this feature.
-	 *
-	 * @param $conn DatabaseBase
-	 * @param $threshold Float
-	 */
-	function postConnectionBackoff( $conn, $threshold );
+	public function scaleLoads( &$loads, $group = false, $wiki = false );
 
 	/**
 	 * Return an estimate of replication lag for each server
 	 *
-	 * @param $serverIndexes
-	 * @param $wiki
+	 * @param array $serverIndexes
+	 * @param string $wiki
 	 *
 	 * @return array
 	 */
-	function getLagTimes( $serverIndexes, $wiki );
+	public function getLagTimes( $serverIndexes, $wiki );
 }
 
-class LoadMonitor_Null implements LoadMonitor {
-	function __construct( $parent ) {
-	}
-
-	function scaleLoads( &$loads, $group = false, $wiki = false ) {
+class LoadMonitorNull implements LoadMonitor {
+	public function __construct( $parent ) {
 	}
 
-	function postConnectionBackoff( $conn, $threshold ) {
+	public function scaleLoads( &$loads, $group = false, $wiki = false ) {
 	}
 
-	/**
-	 * @param $serverIndexes
-	 * @param $wiki
-	 * @return array
-	 */
-	function getLagTimes( $serverIndexes, $wiki ) {
+	public function getLagTimes( $serverIndexes, $wiki ) {
 		return array_fill_keys( $serverIndexes, 0 );
 	}
 }
@@ -97,58 +71,44 @@ class LoadMonitor_Null implements LoadMonitor {
  *
  * @ingroup Database
  */
-class LoadMonitor_MySQL implements LoadMonitor {
+class LoadMonitorMySQL implements LoadMonitor {
+	/** @var LoadBalancer */
+	public $parent;
+	/** @var BagOStuff */
+	protected $cache;
 
-	/**
-	 * @var LoadBalancer
-	 */
-	var $parent;
+	public function __construct( $parent ) {
+		global $wgMemc;
 
-	/**
-	 * @param LoadBalancer $parent
-	 */
-	function __construct( $parent ) {
 		$this->parent = $parent;
+		$this->cache = $wgMemc ?: wfGetMainCache();
 	}
 
-	/**
-	 * @param $loads
-	 * @param $group bool
-	 * @param $wiki bool
-	 */
-	function scaleLoads( &$loads, $group = false, $wiki = false ) {
+	public function scaleLoads( &$loads, $group = false, $wiki = false ) {
 	}
 
-	/**
-	 * @param $serverIndexes
-	 * @param $wiki
-	 * @return array
-	 */
-	function getLagTimes( $serverIndexes, $wiki ) {
+	public function getLagTimes( $serverIndexes, $wiki ) {
 		if ( count( $serverIndexes ) == 1 && reset( $serverIndexes ) == 0 ) {
 			// Single server only, just return zero without caching
 			return array( 0 => 0 );
 		}
 
-		wfProfileIn( __METHOD__ );
+		$section = new ProfileSection( __METHOD__ );
+
 		$expiry = 5;
 		$requestRate = 10;
 
-		global $wgMemc;
-		if ( empty( $wgMemc ) ) {
-			$wgMemc = wfGetMainCache();
-		}
-
+		$cache = $this->cache;
 		$masterName = $this->parent->getServerName( 0 );
 		$memcKey = wfMemcKey( 'lag_times', $masterName );
-		$times = $wgMemc->get( $memcKey );
+		$times = $cache->get( $memcKey );
 		if ( is_array( $times ) ) {
 			# Randomly recache with probability rising over $expiry
 			$elapsed = time() - $times['timestamp'];
 			$chance = max( 0, ( $expiry - $elapsed ) * $requestRate );
 			if ( mt_rand( 0, $chance ) != 0 ) {
 				unset( $times['timestamp'] ); // hide from caller
-				wfProfileOut( __METHOD__ );
+
 				return $times;
 			}
 			wfIncrStats( 'lag_cache_miss_expired' );
@@ -157,15 +117,15 @@ class LoadMonitor_MySQL implements LoadMonitor {
 		}
 
 		# Cache key missing or expired
-		if ( $wgMemc->add( "$memcKey:lock", 1, 10 ) ) {
+		if ( $cache->add( "$memcKey:lock", 1, 10 ) ) {
 			# Let this process alone update the cache value
-			$unlocker = new ScopedCallback( function() use ( $wgMemc, $memcKey ) {
-				$wgMemc->delete( $memcKey );
+			$unlocker = new ScopedCallback( function () use ( $cache, $memcKey ) {
+				$cache->delete( $memcKey );
 			} );
 		} elseif ( is_array( $times ) ) {
 			# Could not acquire lock but an old cache exists, so use it
 			unset( $times['timestamp'] ); // hide from caller
-			wfProfileOut( __METHOD__ );
+
 			return $times;
 		}
 
@@ -177,34 +137,19 @@ class LoadMonitor_MySQL implements LoadMonitor {
 				$times[$i] = $conn->getLag();
 			} elseif ( false !== ( $conn = $this->parent->openConnection( $i, $wiki ) ) ) {
 				$times[$i] = $conn->getLag();
+				// Close the connection to avoid sleeper connections piling up.
+				// Note that the caller will pick one of these DBs and reconnect,
+				// which is slightly inefficient, but this only matters for the lag
+				// time cache miss cache, which is far less common that cache hits.
+				$this->parent->closeConnection( $conn );
 			}
 		}
 
 		# Add a timestamp key so we know when it was cached
 		$times['timestamp'] = time();
-		$wgMemc->set( $memcKey, $times, $expiry + 10 );
+		$cache->set( $memcKey, $times, $expiry + 10 );
 		unset( $times['timestamp'] ); // hide from caller
 
-		wfProfileOut( __METHOD__ );
 		return $times;
 	}
-
-	/**
-	 * @param $conn DatabaseBase
-	 * @param $threshold
-	 * @return int
-	 */
-	function postConnectionBackoff( $conn, $threshold ) {
-		if ( !$threshold ) {
-			return 0;
-		}
-		$status = $conn->getMysqlStatus( "Thread%" );
-		if ( $status['Threads_running'] > $threshold ) {
-			$server = $conn->getProperty( 'mServer' );
-			wfLogDBError( "LB backoff from $server - Threads_running = {$status['Threads_running']}\n" );
-			return $status['Threads_connected'];
-		} else {
-			return 0;
-		}
-	}
 }