From: Aaron Schulz <aschulz@wikimedia.org>
Date: Thu, 28 May 2015 17:04:19 +0000 (-0700)
Subject: objectcache: Add WANObjectCache::resetCheckKey() method
X-Git-Tag: 1.31.0-rc.0~10784^2
X-Git-Url: http://git.cyclocoop.org/data/Luca_Pacioli_%28Gemaelde%29.jpeg?a=commitdiff_plain;h=7d5f3efa2fae29db28881ec739e5e7011cf03a51;p=lhc%2Fweb%2Fwiklou.git

objectcache: Add WANObjectCache::resetCheckKey() method

Change-Id: I6f8b97c1f4511534e1ab2656f472adee491f9d9f
---

diff --git a/includes/libs/objectcache/WANObjectCache.php b/includes/libs/objectcache/WANObjectCache.php
index c32efb9776..e8837b330b 100644
--- a/includes/libs/objectcache/WANObjectCache.php
+++ b/includes/libs/objectcache/WANObjectCache.php
@@ -300,8 +300,10 @@ class WANObjectCache {
 
 		$time = self::parsePurgeValue( $this->cache->get( $key ) );
 		if ( $time === false ) {
-			$time = microtime( true );
+			// Casting assures identical floats for the next getCheckKeyTime() calls
+			$time = (string)microtime( true );
 			$this->cache->add( $key, self::PURGE_VAL_PREFIX . $time, self::CHECK_KEY_TTL );
+			$time = (float)$time;
 		}
 
 		return $time;
@@ -320,6 +322,13 @@ class WANObjectCache {
 	 * avoid race conditions where dependent keys get updated with a
 	 * stale value (e.g. from a DB slave).
 	 *
+	 * This is typically useful for keys with static names or some cases
+	 * dynamically generated names where a low number of combinations exist.
+	 * When a few important keys get a large number of hits, a high cache
+	 * time is usually desired as well as lockTSE logic. The resetCheckKey()
+	 * method is less appropriate in such cases since the "time since expiry"
+	 * cannot be inferred.
+	 *
 	 * Note that "check" keys won't collide with other regular keys
 	 *
 	 * @see WANObjectCache::get()
@@ -336,6 +345,39 @@ class WANObjectCache {
 		return $this->relayPurge( $key, self::CHECK_KEY_TTL ) && $ok;
 	}
 
+	/**
+	 * Delete a "check" key from all clusters, invalidating keys that use it
+	 *
+	 * This is similar to touchCheckKey() in that keys using it via
+	 * getWithSetCallback() will be invalidated. The differences are:
+	 *   a) The timestamp will be deleted from all caches and lazily
+	 *      re-initialized when accessed (rather than set everywhere)
+	 *   b) Thus, dependent keys will be known to be invalid, but not
+	 *      for how long (they are treated as "just" purged), which
+	 *      effects any lockTSE logic in getWithSetCallback()
+	 * The advantage is that this does not place high TTL keys on every cache
+	 * server, making it better for code that will cache many different keys
+	 * and either does not use lockTSE or uses a low enough TTL anyway.
+	 *
+	 * This is typically useful for keys with dynamically generated names
+	 * where a high number of combinations exist.
+	 *
+	 * Note that "check" keys won't collide with other regular keys
+	 *
+	 * @see WANObjectCache::touchCheckKey()
+	 * @see WANObjectCache::get()
+	 *
+	 * @param string $key Cache key
+	 * @return bool True if the item was purged or not found, false on failure
+	 */
+	final public function resetCheckKey( $key ) {
+		$key = self::TIME_KEY_PREFIX . $key;
+		// Update the local cluster immediately
+		$ok = $this->cache->delete( $key );
+		// Publish the purge to all clusters
+		return $this->relayDelete( $key ) && $ok;
+	}
+
 	/**
 	 * Method to fetch/regenerate cache keys
 	 *
@@ -545,6 +587,26 @@ class WANObjectCache {
 		return $ok;
 	}
 
+	/**
+	 * Do the actual async bus delete of a key
+	 *
+	 * @param string $key Cache key
+	 * @return bool Success
+	 */
+	protected function relayDelete( $key ) {
+		$event = $this->cache->modifySimpleRelayEvent( array(
+			'cmd' => 'delete',
+			'key' => $key,
+		) );
+
+		$ok = $this->relayer->notify( "{$this->pool}:purge", $event );
+		if ( !$ok ) {
+			$this->lastRelayError = self::ERR_RELAY;
+		}
+
+		return $ok;
+	}
+
 	/**
 	 * Check if a key should be regenerated (using random probability)
 	 *
diff --git a/tests/phpunit/includes/objectcache/WANObjectCacheTest.php b/tests/phpunit/includes/objectcache/WANObjectCacheTest.php
index 10f64be716..9b4eca7e50 100644
--- a/tests/phpunit/includes/objectcache/WANObjectCacheTest.php
+++ b/tests/phpunit/includes/objectcache/WANObjectCacheTest.php
@@ -224,6 +224,7 @@ class WANObjectCacheTest extends MediaWikiTestCase {
 
 	/**
 	 * @covers WANObjectCache::touchCheckKey()
+	 * @covers WANObjectCache::resetCheckKey()
 	 * @covers WANObjectCache::getCheckKeyTime()
 	 */
 	public function testTouchKeys() {
@@ -250,5 +251,13 @@ class WANObjectCacheTest extends MediaWikiTestCase {
 
 		$t4 = $this->cache->getCheckKeyTime( $key );
 		$this->assertEquals( $t3, $t4, 'Check key time did not change' );
+
+		usleep( 1 );
+		$this->cache->resetCheckKey( $key );
+		$t5 = $this->cache->getCheckKeyTime( $key );
+		$this->assertGreaterThan( $t4, $t5, 'Check key time increased' );
+
+		$t6 = $this->cache->getCheckKeyTime( $key );
+		$this->assertEquals( $t5, $t6, 'Check key time did not change' );
 	}
 }