Issue status update for http://drupal.org/node/19298 Project: Drupal Version: cvs Component: base system Category: feature requests Priority: normal Assigned to: Jeremy@kerneltrap.org Reported by: Jeremy@kerneltrap.org Updated by: Dries Status: patch Looks like this patch can go in soon after the DRUPAL-4-6 has been created. You'll want to update the cache related documentation in system_help() (then again it might not be necessary). I wouldn't bother making this more configurable until we have evaluated/tested this some more. I'm very interested in testing this out or in getting some performance numbers. Dries Previous comments: ------------------------------------------------------------------------ March 23, 2005 - 06:32 : Jeremy@kerneltrap.org Attachment: http://drupal.org/files/issues/database.mysql_1.patch (382 bytes) Drupal's existing caching mechanism doesn't perform well on highly dynamic websites in which the cache is flushed frequently. One example is a site that is under attack by a spambot that is posting spam comments every few seconds, causing all cached pages to be flushed every few seconds. The attached patches provide the following cache methods: 1) CACHE_DISABLED: no caching. This is unchanged from before. 2) CACHE_ENABLED_STRICT: This is Drupal's existing caching method, in which the cache is flushed immediately whenever it contains invalid data. 3) CACHE_ENABLED_LOOSE: This is the new caching method (feel free to suggest a better name, this is the best I could come up with tonight). Essentially, it immediately flushes the cache only for specific users who have modified cached data (whether or not they are logged in), delaying the flushing of data for other users by several minutes. This feature requires a new 'cache' field in the sessions table to track the cache status for each user, whether or not they are logged in. A one line change to the system.module updates the cache configuration settings to include an additional option for loose caching. The rest of the changes are in bootstrap.inc, as follows: - cache_clear_all: if strict caching is enabled, nothing is changed. If loose caching is enabled, we delay the flushing of the entire cache for 5 minutes. Instead, we update this user's cache field in the sessions table so we know any cache pages created before the current time are no longer valid for this user. We only set the global "cache_flush" variable if it's not already set. If the global "cache_flush" variable was set more than 5 minutes ago, we flush all cache pages that were expired when the "cache_flush" variable was set. - cache_get: if strict caching is enabled, nothing is changed. If loose caching is enabled, we first check the global "cache_flush" variable and if older than 5 minutes we do a garbage collection call to cache_clear_all. Next, we see if there is a valid cache entry for us. If the cache entry is older than our session table's "cache" field, we don't use it. This will cause the cache to be regenerated by the current user, and ultimately updated for all users. Attached is the patch to database.mysql. To add manually, execute the following: ALTER TABLE sessions ADD cache int(11) NOT NULL default '0' AFTER timestamp; ------------------------------------------------------------------------ March 23, 2005 - 06:33 : Jeremy@kerneltrap.org Attachment: http://drupal.org/files/issues/system.module_5.patch (1.49 KB) Attached is the patch for the system.module, adding the new cache configuration option. ------------------------------------------------------------------------ March 23, 2005 - 06:36 : Jeremy@kerneltrap.org Attachment: http://drupal.org/files/issues/bootstrap.inc.patch (3.62 KB) And finally, the patch for bootstrap.inc. BTW: Do we want to make the 'cache_flush_delay' configurable? Or perhaps just stick with a sane default? Perhaps 60 seconds is more sane than 300 seconds? ------------------------------------------------------------------------ March 23, 2005 - 06:44 : Jeremy@kerneltrap.org Attachment: http://drupal.org/files/issues/bootstrap.inc_0.patch (3.61 KB) Updated version of the bootstrap.inc.patch, removing an erroneous "else" that prevented the cache from being properly updated for a specific user after a delayed flush. ------------------------------------------------------------------------ March 23, 2005 - 09:12 : Anonymous Looks very good. Please provide patches in one file, though. Gerhard ------------------------------------------------------------------------ March 23, 2005 - 10:35 : stefan nagtegaal First of all, I do not have huge sites under my juristriction, so maybe my points here aren't valid.. If so, tell me and I'll shut up.. I took a look at your patches, and I truly do not understand why you set more Caching methods in 'admin/system'. I think that it would be better if we stay with the cuurent options (Enabled, Disabled) and let Drupal suggest the way of the caching methods (CACHE_ENABLED_LOOSE and CACHE_ENABLED_SCTRICT). This would make your patch to system.module a little smaller and easier to understand for newbies.. Also, as you said yourself, I don't see why we should make the 'cache_flush_delay' configurable. I mean, how would you know what a good time would be? Couldn't drupal find out the right value for that, so the administrator doesn't have to? Again, I'm not speaking as someone who is in need of something like this, but I can understand some people are.. What I'm trying to tell, is that the idea is probably pretty good only with less options and more automagical cache settings it would be more userfriendly ad doesn't scare off newbies (or me)...