The Services DC fail-over test finished without user impact, and traffic is now switched back to eqiad.
We found an issue with one of the Cassandra nodes running out of memory after switching update processing to codfw, as well as a hick-up with one instance in eqiad. Due to the redundant set-up, this did not affect operations. We are investigating these issues, and will address them before the general fail-over test in April. Many thanks to Marko Obrovac, Eric Evans (Services), Filippo Giunchedi, Giuseppe Lavagetto and Emanuele Rocca (Operations), who prepared the infrastructure to make the switch-over this smooth. Gabriel On Thu, Mar 17, 2016 at 3:10 AM, Marko Obrovac <mobro...@wikimedia.org> wrote: > FYI, the test has started. We are in the process of switching the traffic to > the Dallas DC. > > Cheers, > Marko > > On 14 March 2016 at 22:54, Marko Obrovac <mobro...@wikimedia.org> wrote: >> >> Hello, >> >> The WMF’s technology department has for this quarter the goal of testing >> and temporarily switching the main operational data centre from Eqiad >> (located in Chicago) to Codfw (located in Dallas)~[1,2]. This includes both >> back-end-processing as well as serving live traffic from it. >> >> As a part of this effort, we are scheduling a switch-over for RESTBase and >> its back-end services, including: Parsoid, the Mobile Content Service, >> CXServer, Mathoid, Citoid, Apertium and Zotero~[3]. Technically, it will not >> be a real switch-over per se, because we will keep all of those services >> active in both DCs. However, external traffic will be directed to the Dallas >> DC only. >> >> === When is it and what does it mean for me? === >> The switch-over test is planned for this Thursday, 2016-03-17. We have >> allotted a three-hour window for this~[4]. There is nothing users should do >> before or after the switch; it will be transparent for them. There are two >> things users should note, though: >> >> 1) At the time of the switch-over, users might receive error responses for >> a while (both 4xx and 5xx status codes). While we will test most of the >> things ahead of time, we cannot test the actual traffic shifting, so small >> bumps might be noticed. >> 2) After the switch to the Dallas DC, users will likely see their response >> latencies slightly elevated. During the test, some requests might experience >> a slightly larger latency. This will occur because all of the services that >> will be responding to live requests still need to contact the main MediaWiki >> cluster, which will remain in Eqiad (the other DC) until a complete >> switch-over of the infrastructure is performed. However, given the multiple >> levels of caching, the 40 ms of penalty to go cross-DC for an uncached API >> request does not seem too taxing. >> >> === Wait, what about my service X running in WMF production? === >> If you are a service owner of one the aforementioned services, there are >> no explicit actions you should take prior to, during or after the >> switch-over test. This test could, however, affect your service depending on >> whether it usually serves live traffic or is mostly operational during >> various internal updates. MediaWiki and JobQueue processing will still be >> performed in Eqiad, so in the latter case your service should not see a >> change in the usage pattern. If, however, your service is mostly in charge >> of responding to live requests coming through RESTBase, those will be >> handled by instances in Codfw. However, as these services are full replicas >> of their Eqiad counterparts and are stateless, no major breakage will >> happen. >> >> Should you have any questions or concerns, don’t hesitate to contact us >> here or on IRC (#wikimedia-services @ freenode). >> >> Best, >> Marko Obrovac, PhD >> Senior Services Engineer >> Wikimedia Foundation >> >> [1] >> https://www.mediawiki.org/wiki/Wikimedia_Engineering/2015-16_Q3_Goals#Technology >> [2] https://phabricator.wikimedia.org/project/profile/1723/ >> [3] https://phabricator.wikimedia.org/T127974 >> [4] >> https://wikitech.wikimedia.org/wiki/Deployments#Thursday.2C.C2.A0March.C2.A017 >> > > > > -- > Marko Obrovac, PhD > Senior Services Engineer > Wikimedia Foundation > > _______________________________________________ > Services mailing list > servi...@lists.wikimedia.org > https://lists.wikimedia.org/mailman/listinfo/services > -- Gabriel Wicke Principal Engineer, Wikimedia Foundation _______________________________________________ Wikitech-l mailing list Wikitech-l@lists.wikimedia.org https://lists.wikimedia.org/mailman/listinfo/wikitech-l
