Some thoughts: * Use a front-end web cache.
The old 'file cache' in MediaWiki probably doesn't work as well as it once did, especially since you're on a recent version of MediaWiki that uses ResourceLoader -- that'll mean dynamic hits happen for styles and scripts even on a cached page -- and even that cached page is going through MediaWiki and requires CPU time and memory. I'm not sure whether any of the cloud-based CDNs play nicely with MediaWiki these days, but you can certainly set up Squid or Varnish on a second Linode box. A proper caching setup that covers both article views and ResourceLoader (load.php stuff) should be able to avoid a *lot* of hits to PHP as long as people are just clicking around. You can also do things like loading static resources (uploaded files, skin images etc) from a separate server, but putting a cache in front should cover much the same requirements as that. * Consider splitting Lucene search to a separate server. Particularly since it's memory intensive, splitting it out will leave more RAM on your main server for handling spikes. * Do some load tests and set maximums appropriately If you've got a lot of MediaWiki hits going simultaneously, that's going to drive up your memory usage. Make sure that hitting the maximum number of server threads doesn't kill you just from loading up Apache+PHP+MediaWiki! -- brion On Wed, Oct 17, 2012 at 3:25 PM, David Gerard <[email protected]> wrote: > The problem: In general, rationalwiki.org is melting under the strain. > We can't quite afford the next step up right this moment, though want > to plan for it, and need to keep things from intermittently blowing up > as they are. > > > We live on a 4GB Linode. I don't have a full handle on what we've got > on it - it's accreted in an ad-hoc fashion with some horrible bodges - > but there's several MediaWikis, only one of which (rationalwiki.org) > has any appreciable traffic. There's Lucene search, which is of course > huge in memory. rationalwiki.org is running via libphp5, the other > wikis are via fastcgi (for no particular reason). The wikis have a > huge pile of extensions, e.g. > http://rationalwiki.org/wiki/Special:Version , a lot of which are > local things. > > Whenever an article hits Reddit,[1] the server suffers under the load. > Typically it goes into swap and thrashes itself to death. If we're > really lucky the oom-killer comes out to play and shoots things > randomly (usually Apache, maybe Lucene). The fun bit: sometimes it > does this for no visible reason, just tips over into swap and promptly > stops talking to the world (my shell session still works slowly). > > Per advice from here I've re-enabled keepalive, setting it to 10 > requests and 2 seconds. This does speed things up a bit for the users. > I haven't put a cache on the front as yet, still letting MediaWiki's > file cache do that. apc is running (99.8% cache hit rate, so that's > fine) and memcached (90% cache hit rate, upped it from 64MB to 128MB > and it's still about 90%). > > So second thing we need to work out what our next stage of evolution > is (the 8GB Linode for $200/mo more? [2] or multiple servers? > Distributed how?) - and the first thing we need to work out how not to > make the box melt in the meantime. > > Clues welcomed! > > > - d. > > > [1] usually a joke article, like > http://rationalwiki.org/wiki/Scientific_evidence_of_evolution_being_a_hoax > ... nothing we've actually worked hard on *hand to forehead* > [2] this appears pretty typical pricing for non-crappy hosting > > _______________________________________________ > MediaWiki-l mailing list > [email protected] > https://lists.wikimedia.org/mailman/listinfo/mediawiki-l > _______________________________________________ MediaWiki-l mailing list [email protected] https://lists.wikimedia.org/mailman/listinfo/mediawiki-l
