Cleaned up $asyncWrites member variable in MultiWriteBagOStuff

[lhc/web/wiklou.git] / includes / objectcache / MultiWriteBagOStuff.php

diff --git a/includes/objectcache/MultiWriteBagOStuff.php b/includes/objectcache/MultiWriteBagOStuff.php
index b5f3bd9..16e842f 100644 (file)
--- a/includes/objectcache/MultiWriteBagOStuff.php
+++ b/includes/objectcache/MultiWriteBagOStuff.php
@@ -31,27 +31,46 @@
 class MultiWriteBagOStuff extends BagOStuff {
        /** @var BagOStuff[] */
        protected $caches;
+       /** @var bool Use async secondary writes */
+       protected $asyncWrites = false;
 
        /**
-        * Constructor. Parameters are:
-        *
-        *   - caches:   This should have a numbered array of cache parameter
-        *               structures, in the style required by $wgObjectCaches. See
-        *               the documentation of $wgObjectCaches for more detail.
+        * $params include:
+        *   - caches:      This should have a numbered array of cache parameter
+        *                  structures, in the style required by $wgObjectCaches. See
+        *                  the documentation of $wgObjectCaches for more detail.
+        *                  BagOStuff objects can also be used as values.
+        *                  The first cache is the primary one, being the first to
+        *                  be read in the fallback chain. Writes happen to all stores
+        *                  in the order they are defined. However, lock()/unlock() calls
+        *                  only use the primary store.
+        *   - replication: Either 'sync' or 'async'. This controls whether writes to
+        *                  secondary stores are deferred when possible. Async writes
+        *                  require the HHVM register_postsend_function() function.
+        *                  Async writes can increase the chance of some race conditions
+        *                  or cause keys to expire seconds later than expected. It is
+        *                  safe to use for modules when cached values: are immutable,
+        *                  invalidation uses logical TTLs, invalidation uses etag/timestamp
+        *                  validation against the DB, or merge() is used to handle races.
         *
         * @param array $params
         * @throws InvalidArgumentException
         */
        public function __construct( $params ) {
                parent::__construct( $params );
+
                if ( !isset( $params['caches'] ) ) {
-                       throw new InvalidArgumentException( __METHOD__ . ': the caches parameter is required' );
+                       throw new InvalidArgumentException( __METHOD__ . ': "caches" parameter required' );
                }
 
                $this->caches = array();
                foreach ( $params['caches'] as $cacheInfo ) {
-                       $this->caches[] = ObjectCache::newFromParams( $cacheInfo );
+                       $this->caches[] = ( $cacheInfo instanceof BagOStuff )
+                               ? $cacheInfo
+                               : ObjectCache::newFromParams( $cacheInfo );
                }
+
+               $this->asyncWrites = isset( $params['replication'] ) && $params['replication'] === 'async';
        }
 
        /**
@@ -121,12 +140,13 @@ class MultiWriteBagOStuff extends BagOStuff {
         * @param string $key
         * @param int $timeout
         * @param int $expiry
+        * @param string $rclass
         * @return bool
         */
-       public function lock( $key, $timeout = 6, $expiry = 6 ) {
+       public function lock( $key, $timeout = 6, $expiry = 6, $rclass = '' ) {
                // Lock only the first cache, to avoid deadlocks
                if ( isset( $this->caches[0] ) ) {
-                       return $this->caches[0]->lock( $key, $timeout, $expiry );
+                       return $this->caches[0]->lock( $key, $timeout, $expiry, $rclass );
                } else {
                        return true;
                }
@@ -174,11 +194,25 @@ class MultiWriteBagOStuff extends BagOStuff {
                $args = func_get_args();
                array_shift( $args );
 
-               foreach ( $this->caches as $cache ) {
-                       if ( !call_user_func_array( array( $cache, $method ), $args ) ) {
-                               $ret = false;
+               foreach ( $this->caches as $i => $cache ) {
+                       if ( $i == 0 || !$this->asyncWrites ) {
+                               // First store or in sync mode: write now and get result
+                               if ( !call_user_func_array( array( $cache, $method ), $args ) ) {
+                                       $ret = false;
+                               }
+                       } else {
+                               // Secondary write in async mode: do not block this HTTP request
+                               $logger = $this->logger;
+                               DeferredUpdates::addCallableUpdate(
+                                       function() use ( $cache, $method, $args, $logger ) {
+                                               if ( !call_user_func_array( array( $cache, $method ), $args ) ) {
+                                                       $logger->warning( "Async $method op failed" );
+                                               }
+                                       }
+                               );
                        }
                }
+
                return $ret;
        }
 
@@ -197,6 +231,7 @@ class MultiWriteBagOStuff extends BagOStuff {
                                $ret = true;
                        }
                }
+
                return $ret;
        }
 }