From: daniel <daniel.kinzler@wikimedia.de>
Date: Thu, 2 Aug 2018 15:49:27 +0000 (+0200)
Subject: Document cross-wiki cache sharing logic.
X-Git-Tag: 1.34.0-rc.0~4567^2
X-Git-Url: https://git.heureux-cyclage.org/?p=lhc%2Fweb%2Fwiklou.git;a=commitdiff_plain;h=63ae40bfad2ea1c3281ce13916a5e2041506f413

Document cross-wiki cache sharing logic.

This makes explicit the fact that some classes can use the local wiki's default
WANObjectCache instance while still sharing cache entries between wikis.

Bug: T198704
Change-Id: Ic29f79e4b4bd6bdaa844049962a163e72a59c45a
---

diff --git a/includes/Storage/NameTableStore.php b/includes/Storage/NameTableStore.php
index 23b2902534..52e8f5b993 100644
--- a/includes/Storage/NameTableStore.php
+++ b/includes/Storage/NameTableStore.php
@@ -66,7 +66,12 @@ class NameTableStore {
 
 	/**
 	 * @param ILoadBalancer $dbLoadBalancer A load balancer for acquiring database connections
-	 * @param WANObjectCache $cache A cache manager for caching data
+	 * @param WANObjectCache $cache A cache manager for caching data. This can be the local
+	 *        wiki's default instance even if $wikiId refers to a different wiki, since
+	 *        makeGlobalKey() is used to constructed a key that allows cached names from
+	 *        the same database to be re-used between wikis. For example, enwiki and frwiki will
+	 *        use the same cache keys for names from the wikidatawiki database, regardless
+	 *        of the cache's default key space.
 	 * @param LoggerInterface $logger
 	 * @param string $table
 	 * @param string $idField
diff --git a/includes/Storage/RevisionStore.php b/includes/Storage/RevisionStore.php
index 0796d620e1..65c0361b63 100644
--- a/includes/Storage/RevisionStore.php
+++ b/includes/Storage/RevisionStore.php
@@ -130,7 +130,12 @@ class RevisionStore
 	 *
 	 * @param ILoadBalancer $loadBalancer
 	 * @param SqlBlobStore $blobStore
-	 * @param WANObjectCache $cache
+	 * @param WANObjectCache $cache A cache for caching revision rows. This can be the local
+	 *        wiki's default instance even if $wikiId refers to a different wiki, since
+	 *        makeGlobalKey() is used to constructed a key that allows cached revision rows from
+	 *        the same database to be re-used between wikis. For example, enwiki and frwiki will
+	 *        use the same cache keys for revision rows from the wikidatawiki database, regardless
+	 *        of the cache's default key space.
 	 * @param CommentStore $commentStore
 	 * @param NameTableStore $contentModelStore
 	 * @param NameTableStore $slotRoleStore
diff --git a/includes/Storage/SqlBlobStore.php b/includes/Storage/SqlBlobStore.php
index 48ffe2c903..d7216c5c72 100644
--- a/includes/Storage/SqlBlobStore.php
+++ b/includes/Storage/SqlBlobStore.php
@@ -94,7 +94,12 @@ class SqlBlobStore implements IDBAccessObject, BlobStore {
 
 	/**
 	 * @param LoadBalancer $dbLoadBalancer A load balancer for acquiring database connections
-	 * @param WANObjectCache $cache A cache manager for caching blobs
+	 * @param WANObjectCache $cache A cache manager for caching blobs. This can be the local
+	 *        wiki's default instance even if $wikiId refers to a different wiki, since
+	 *        makeGlobalKey() is used to constructed a key that allows cached blobs from the
+	 *        same database to be re-used between wikis. For example, enwiki and frwiki will
+	 *        use the same cache keys for blobs from the wikidatawiki database, regardless of
+	 *        the cache's default key space.
 	 * @param bool|string $wikiId The ID of the target wiki database. Use false for the local wiki.
 	 */
 	public function __construct(