Hi Everyone,

just a wanted to post a quick summary of what I did today in order to significantly reduce the SiteStore related memcached traffic.

I stumbled upon this comment https://phabricator.wikimedia.org/T58602#808530 and thus poked a bit at when we load sites from memcached. During that I found that we still were loading the sites basically all the time. To get the number of that down, I uploaded the following patches that have been reviewed, merged and even deployed yet (thanks for the reviews Daniel and Katie):

* Don't lookup Sites from mc for the 'languageLinkSiteGroup' setting: https://gerrit.wikimedia.org/r/177419 * Don't load all sites for LangLinkHandler: https://gerrit.wikimedia.org/r/177429 * Don't access sites on WikibaseClient::getEntityIdForTitle: https://gerrit.wikimedia.org/r/177434

That lead to a noticeable memcached traffic change (see attachment). Memcached traffic graphs: https://ganglia.wikimedia.org/latest/graph_all_periods.php?c=Memcached% 20eqiad&m=cpu_report&r=hour&s=by% 20name&hc=4&mc=2&st=1417641558&g=network_report&z=large

I still have https://gerrit.wikimedia.org/r/177416 in review, which slightly changes the behavior of the other projects sidebar, but I think that this change also has quite some potential to reduce memcached traffic even further. Would be great if we could get that ready for backporting until Monday.

Cheers,

Marius