Remove "memCache" field from LoadBalancer

The only user was LoadMonitor, which is converted to only use the WAN and server caches. Previously, the lock() calls there were useless since LBFactory never injected "memcCache" to LoadBalancer, ergo making it EmptyBagOStuff in LoadMonitor. Change-Id: I0c7793d47b93b763dee478d16fb87ec637dc6cab

Author: AaronSchulz

includes/libs/rdbms/loadbalancer/ILoadBalancer.php

@@ -94,7 +94,6 @@ interface ILoadBalancer {
  * - readOnlyReason : Reason the master DB is read-only if so [optional]
  * - waitTimeout : Maximum time to wait for replicas for consistency [optional]
  * - srvCache : BagOStuff object for server cache [optional]
- * - memCache : BagOStuff object for cluster memory cache [optional]
  * - wanCache : WANObjectCache object [optional]
  * - chronologyProtector: ChronologyProtector object [optional]
  * - hostname : The name of the current server [optional]

includes/libs/rdbms/loadbalancer/LoadBalancer.php

@@ -62,8 +62,6 @@ class LoadBalancer implements ILoadBalancer {
 private $chronProt;
 /** @var BagOStuff */
 private $srvCache;
-/** @var BagOStuff */
-private $memCache;
 /** @var WANObjectCache */
 private $wanCache;
 /** @var object|string Class name or object With profileIn/profileOut methods */
@@ -187,11 +185,6 @@ public function __construct( array $params ) {
 } else {
 $this->srvCache = new EmptyBagOStuff();
 }
-if ( isset( $params['memCache'] ) ) {
-$this->memCache = $params['memCache'];
-} else {
-$this->memCache = new EmptyBagOStuff();
-}
 if ( isset( $params['wanCache'] ) ) {
 $this->wanCache = $params['wanCache'];
 } else {
@@ -244,7 +237,7 @@ private function getLoadMonitor() {
 }
 
 $this->loadMonitor = new $class(
-$this, $this->srvCache, $this->memCache, $this->loadMonitorConfig );
+$this, $this->srvCache, $this->wanCache, $this->loadMonitorConfig );
 $this->loadMonitor->setLogger( $this->replLogger );
 }
 

includes/libs/rdbms/loadmonitor/ILoadMonitor.php

@@ -25,6 +25,7 @@
 
 use Psr\Log\LoggerAwareInterface;
 use BagOStuff;
+use WANObjectCache;
 
 /**
  * An interface for database load monitoring
@@ -37,11 +38,11 @@ interface ILoadMonitor extends LoggerAwareInterface {
  *
  * @param ILoadBalancer $lb LoadBalancer this instance serves
  * @param BagOStuff $sCache Local server memory cache
- * @param BagOStuff $cCache Local cluster memory cache
+ * @param WANObjectCache $wCache Local cluster memory cache
  * @param array $options Options map
  */
 public function __construct(
-ILoadBalancer $lb, BagOStuff $sCache, BagOStuff $cCache, array $options = []
+ILoadBalancer $lb, BagOStuff $sCache, WANObjectCache $wCache, array $options = []
 );
 
 /**

includes/libs/rdbms/loadmonitor/LoadMonitor.php

@@ -25,6 +25,7 @@
 use Psr\Log\NullLogger;
 use Wikimedia\ScopedCallback;
 use BagOStuff;
+use WANObjectCache;
 
 /**
  * Basic DB load monitor with no external dependencies
@@ -37,8 +38,8 @@ class LoadMonitor implements ILoadMonitor {
 protected $parent;
 /** @var BagOStuff */
 protected $srvCache;
-/** @var BagOStuff */
-protected $mainCache;
+/** @var WANObjectCache */
+protected $wanCache;
 /** @var LoggerInterface */
 protected $replLogger;
 
@@ -48,11 +49,11 @@ class LoadMonitor implements ILoadMonitor {
 const VERSION = 1; // cache key version
 
 public function __construct(
-ILoadBalancer $lb, BagOStuff $srvCache, BagOStuff $cache, array $options = []
+ILoadBalancer $lb, BagOStuff $srvCache, WANObjectCache $wCache, array $options = []
 ) {
 $this->parent = $lb;
 $this->srvCache = $srvCache;
-$this->mainCache = $cache;
+$this->wanCache = $wCache;
 $this->replLogger = new NullLogger();
 
 $this->movingAveRatio = isset( $options['movingAveRatio'] )
@@ -109,7 +110,7 @@ protected function getServerStates( array $serverIndexes, $domain ) {
 $staleValue = $value ?: false;
 
 # (b) Check the shared cache and backfill APC
-$value = $this->mainCache->get( $key );
+$value = $this->wanCache->get( $key );
 if ( $value && $value['timestamp'] > ( microtime( true ) - $ttl ) ) {
 $this->srvCache->set( $key, $value, $staleTTL );
 $this->replLogger->debug( __METHOD__ . ": got lag times ($key) from main cache" );
@@ -119,12 +120,12 @@ protected function getServerStates( array $serverIndexes, $domain ) {
 $staleValue = $value ?: $staleValue;
 
 # (c) Cache key missing or expired; regenerate and backfill
-if ( $this->mainCache->lock( $key, 0, 10 ) ) {
-# Let this process alone update the cache value
-$cache = $this->mainCache;
+if ( $this->srvCache->lock( $key, 0, 10 ) ) {
+# Let only this process update the cache value on this server
+$sCache = $this->srvCache;
 /** @noinspection PhpUnusedLocalVariableInspection */
-$unlocker = new ScopedCallback( function () use ( $cache, $key ) {
-$cache->unlock( $key );
+$unlocker = new ScopedCallback( function () use ( $sCache, $key ) {
+$sCache->unlock( $key );
 } );
 } elseif ( $staleValue ) {
 # Could not acquire lock but an old cache exists, so use it
@@ -196,7 +197,7 @@ protected function getServerStates( array $serverIndexes, $domain ) {
 'weightScales' => $weightScales,
 'timestamp' => microtime( true )
 ];
-$this->mainCache->set( $key, $value, $staleTTL );
+$this->wanCache->set( $key, $value, $staleTTL );
 $this->srvCache->set( $key, $value, $staleTTL );
 $this->replLogger->info( __METHOD__ . ": re-calculated lag times ($key)" );
 

includes/libs/rdbms/loadmonitor/LoadMonitorMySQL.php

@@ -22,6 +22,7 @@
 namespace Wikimedia\Rdbms;
 
 use BagOStuff;
+use WANObjectCache;
 
 /**
  * Basic MySQL load monitor with no external dependencies
@@ -34,9 +35,9 @@ class LoadMonitorMySQL extends LoadMonitor {
 private $warmCacheRatio;
 
 public function __construct(
-ILoadBalancer $lb, BagOStuff $srvCache, BagOStuff $cache, array $options = []
+ILoadBalancer $lb, BagOStuff $srvCache, WANObjectCache $wCache, array $options = []
 ) {
-parent::__construct( $lb, $srvCache, $cache, $options );
+parent::__construct( $lb, $srvCache, $wCache, $options );
 
 $this->warmCacheRatio = isset( $options['warmCacheRatio'] )
 ? $options['warmCacheRatio']

includes/libs/rdbms/loadmonitor/LoadMonitorNull.php

@@ -23,10 +23,11 @@
 
 use Psr\Log\LoggerInterface;
 use BagOStuff;
+use WANObjectCache;
 
 class LoadMonitorNull implements ILoadMonitor {
 public function __construct(
-ILoadBalancer $lb, BagOStuff $sCache, BagOStuff $cCache, array $options = []
+ILoadBalancer $lb, BagOStuff $sCache, WANObjectCache $wCache, array $options = []
 ) {
 }