User: Migrate from foreign cache to global cache for UserRightsProxy

Avoid having one wiki access another wiki's local keyspace.
Instead, use the global keyspace to share values across wikis.

Also, imitating wfMemcKey from wfForeignMemcKey was semantically
incorrect due to $wgCachePrefix having precedence. Most interfaces
(e.g. UserRightsProxy, FileRepo, JobQueue etc.) only have access
to the wiki id (dbname + prefix). The local cache configuration
for wgCachePrefix is not and shouldn't have to be exposed.

Start enforcing that local cache keys are left private and
to share keys, one must use global keys.

Global keys (prefixed with "global:") have their own space and we
can use the wiki-id as regular key segment for keys about users.

Also:
* Expose a method to keep formatting of this key in one place.
  As it used used in many different places in core, as well
  as in CentralAuth.
* Make use of wfWikiId() in getDefaultKeyspace() to avoid
  duplicating this logic.

Change-Id: I58836a24b9e239f460ab489bd2fe8ced8259833c

includes/User.php

@@ -387,6 +387,25 @@ class User implements IDBAccessObject {
 		return true;
 	}
 
+	/**
+	 * @since 1.27
+	 * @param string $wikiId
+	 * @param integer $userId
+	 */
+	public static function purge( $wikiId, $userId ) {
+		$cache = ObjectCache::getMainWANInstance();
+		$cache->delete( $cache->makeGlobalKey( 'user', 'id', $wikiId, $userId ) );
+	}
+
+	/**
+	 * @since 1.27
+	 * @param WANObjectCache $cache
+	 * @return string
+	 */
+	protected function getCacheKey( WANObjectCache $cache ) {
+		return $cache->makeGlobalKey( 'user', 'id', wfWikiID(), $this->mId );
+	}
+
 	/**
 	 * Load user data from shared cache, given mId has already been set.
 	 *
@@ -399,8 +418,8 @@ class User implements IDBAccessObject {
 			return false;
 		}
 
-		$key = wfMemcKey( 'user', 'id', $this->mId );
-		$data = ObjectCache::getMainWANInstance()->get( $key );
+		$cache = ObjectCache::getMainWANInstance();
+		$data = $cache->get( $this->getCacheKey( $cache ) );
 		if ( !is_array( $data ) || $data['mVersion'] < self::VERSION ) {
 			// Object is expired
 			return false;
@@ -439,7 +458,7 @@ class User implements IDBAccessObject {
 		$opts = Database::getCacheSetOptions( wfGetDB( DB_SLAVE ) );
 
 		$cache = ObjectCache::getMainWANInstance();
-		$key = wfMemcKey( 'user', 'id', $this->mId );
+		$key = $this->getCacheKey( $cache );
 		$cache->set( $key, $data, $cache::TTL_HOUR, $opts );
 	}
 
@@ -2228,17 +2247,17 @@ class User implements IDBAccessObject {
 	 * @param string $mode Use 'refresh' to clear now; otherwise before DB commit
 	 */
 	public function clearSharedCache( $mode = 'changed' ) {
-		$id = $this->getId();
-		if ( !$id ) {
+		if ( !$this->getId() ) {
 			return;
 		}
 
-		$key = wfMemcKey( 'user', 'id', $id );
+		$cache = ObjectCache::getMainWANInstance();
+		$key = $this->getCacheKey( $cache );
 		if ( $mode === 'refresh' ) {
-			ObjectCache::getMainWANInstance()->delete( $key, 1 );
+			$cache->delete( $key, 1 );
 		} else {
-			wfGetDB( DB_MASTER )->onTransactionPreCommitOrIdle( function() use ( $key ) {
-				ObjectCache::getMainWANInstance()->delete( $key );
+			wfGetDB( DB_MASTER )->onTransactionPreCommitOrIdle( function() use ( $cache, $key ) {
+				$cache->delete( $key );
 			} );
 		}
 	}

includes/UserRightsProxy.php

@@ -278,9 +278,10 @@ class UserRightsProxy {
 			array( 'user_id' => $this->id ),
 			__METHOD__ );
 
-		$key = wfForeignMemcKey( $this->database, false, 'user', 'id', $this->id );
-		$this->db->onTransactionPreCommitOrIdle( function() use ( $key ) {
-			ObjectCache::getMainWANInstance()->delete( $key );
+		$wikiId = $this->db->getWikiID();
+		$userId = $this->id;
+		$this->db->onTransactionPreCommitOrIdle( function() use ( $wikiId, $userId ) {
+			User::purge( $wikiId, $userId );
 		} );
 	}
 }

includes/objectcache/ObjectCache.php

@@ -137,19 +137,14 @@ class ObjectCache {
 	 * @return string
 	 */
 	public static function getDefaultKeyspace() {
-		global $wgCachePrefix, $wgDBname, $wgDBprefix;
+		global $wgCachePrefix;
 
 		$keyspace = $wgCachePrefix;
 		if ( is_string( $keyspace ) && $keyspace !== '' ) {
 			return $keyspace;
 		}
 
-		$keyspace = $wgDBname;
-		if ( is_string( $wgDBprefix ) && $wgDBprefix !== '' ) {
-			$keyspace .= '-' . $wgDBprefix;
-		}
-
-		return $keyspace;
+		return wfWikiID();
 	}
 
 	/**