Index: README.txt =================================================================== RCS file: /cvs/drupal-contrib/contributions/modules/memcache/README.txt,v retrieving revision 1.4.2.10.2.4 retrieving revision 1.4.2.10.2.5 diff -u -r1.4.2.10.2.4 -r1.4.2.10.2.5 --- README.txt 25 Jan 2009 04:08:34 -0000 1.4.2.10.2.4 +++ README.txt 29 Jan 2009 18:01:47 -0000 1.4.2.10.2.5 @@ -1,4 +1,4 @@ -// $Id: README.txt,v 1.4.2.10.2.4 2009/01/25 04:08:34 jvandyk Exp $ +// $Id: README.txt,v 1.4.2.10.2.5 2009/01/29 18:01:47 jeremy Exp $ ## INSTALLATION ## @@ -35,8 +35,8 @@ have enough memory allocated to memcache to store everything (including the page cache), otherwise the cache misses will negate the benefit of the cache hits. -Note that memcache.db.inc supports minimum cache lifetime settings while -memcache.inc does not. For the difference, see these diagrams: +Note that memcache.db.inc support a global minimum cache lifetime, whereas +memcache.inc tracks the minimum cache lifetime on a per-table basis: http://www.lullabot.com/files/memcache-inc.png http://www.lullabot.com/files/memcache-db-inc.png Index: dmemcache.inc =================================================================== RCS file: /cvs/drupal-contrib/contributions/modules/memcache/dmemcache.inc,v retrieving revision 1.1.2.7.2.2 retrieving revision 1.1.2.7.2.4 diff -u -r1.1.2.7.2.2 -r1.1.2.7.2.4 --- dmemcache.inc 1 Nov 2008 12:32:13 -0000 1.1.2.7.2.2 +++ dmemcache.inc 26 Jan 2009 21:12:04 -0000 1.1.2.7.2.4 @@ -1,5 +1,5 @@ get($full_key); if ($result) { - $_memcache_statistics['hit'][] = $key; + // We check $result->expire to see if the object has expired. If so, we + // try and grab a lock. If we get the lock, we return FALSE instead of + // the cached object which should cause it to be rebuilt. If we do not + // get the lock, we return the cached object. The goal here is to avoid + // cache stampedes. + // By default the cache stampede semaphore is held for 15 seconds. This + // can be adjusted by setting the memcache_stampede_semaphore variable. + // TODO: Can we log when a sempahore expires versus being intentionally + // freed to track when this is happening? + if ($result->expire && $result->expire <= time() && $mc->add($full_key .'_semaphore', '', FALSE, variable_get('memcache_stampede_semaphore', 15))) { + $result = FALSE; + } + else { + $_memcache_statistics['hit'][] = $key; + } } return $result; } Index: memcache-session.inc =================================================================== RCS file: /cvs/drupal-contrib/contributions/modules/memcache/memcache-session.inc,v retrieving revision 1.1.2.2.2.8 retrieving revision 1.1.2.2.2.10 diff -u -r1.1.2.2.2.8 -r1.1.2.2.2.10 --- memcache-session.inc 26 Jan 2009 15:11:08 -0000 1.1.2.2.2.8 +++ memcache-session.inc 14 Jul 2009 22:07:11 -0000 1.1.2.2.2.10 @@ -1,5 +1,7 @@ session); unset($user->session_data_present_at_load); + // Store the session id so we can locate the session with the user id. + $user->sid = $key; dmemcache_set($user->uid, $user, ini_get('session.gc_maxlifetime'), 'users'); } @@ -161,9 +165,14 @@ } /** - * End a specific user's session. Not implemented. + * End a specific user's session. */ function sess_destroy_uid($uid) { + $user = dmemcache_get($uid, 'users'); + if (is_object($user) && isset($user->sid)) { + dmemcache_delete($user->sid, 'session'); + } + dmemcache_delete($uid, 'users'); } function sess_gc($lifetime) { Index: memcache.inc =================================================================== RCS file: /cvs/drupal-contrib/contributions/modules/memcache/memcache.inc,v retrieving revision 1.15.2.8.2.3 retrieving revision 1.15.2.8.2.6 diff -u -r1.15.2.8.2.3 -r1.15.2.8.2.6 --- memcache.inc 19 Dec 2008 14:05:58 -0000 1.15.2.8.2.3 +++ memcache.inc 13 Jul 2009 21:33:44 -0000 1.15.2.8.2.6 @@ -1,5 +1,5 @@ created && $cache_flush && + ($cache->created < $cache_flush) && + ((time() - $cache->created >= $cache_lifetime)) || + (is_array($cache_tables) && $cache_tables[$table] && + $cache_tables[$table] > $cache->created)) { + // Cache item expired, return NULL. + return 0; + } + return $cache; + } + return 0; } /** @@ -57,9 +75,13 @@ // Save to memcache if ($expire == CACHE_TEMPORARY) { - $expire = variable_get('cache_lifetime', 2591999); + $expire = 2591999; } - dmemcache_set($cid, $cache, $expire, $table); + // We manually track the expire time in $cache->expire. When the object + // expires, we only allow one request to rebuild it to avoid cache stampedes. + // Other requests for the expired object while it is still being rebuilt get + // the expired object. + dmemcache_set($cid, $cache, 0, $table); } /** @@ -103,7 +125,29 @@ } } else if ($cid == '*' || $wildcard === TRUE) { - dmemcache_flush($table); + if (variable_get('cache_lifetime', 0)) { + // Update the timestamp of the last global flushing of this table. When + // retrieving data from this table, we will compare the cache creation + // time minus the cache_flush time to the cache_lifetime to determine + // whether or not the cached item is still valid. + variable_set("cache_flush_$table", time()); + + // We store the time in the current user's session which is saved into + // the sessions table by sess_write(). We then simulate that the cache + // was flushed for this user by not returning cached data to this user + // that was cached before the timestamp. + if (is_array($_SESSION['cache_flush'])) { + $cache_tables = $_SESSION['cache_flush']; + } + else { + $cache_tables = array(); + } + $cache_tables[$table] = time(); + $_SESSION['cache_flush'] = $cache_tables; + } + else { + dmemcache_flush($table); + } } else { dmemcache_delete($cid, $table);