Hi all,
The first part of this switch completed successfully today. The total time in which the projects were in read-only was approximately 17 minutes.
There were a few hiccups that were or still are being dealt with, the most major ones identified so far being:
- The switch to codfw in combination with what looks like a ContentTranslation bug resulted into an overload of the x1 database shard which in turn affected Echo & Flow. The total outage for Echo & Flow was from 15:36 until 16:18 UTC.
ContentTranslation was also misbehaving since 15:36 and was disabled on all Wikipedias at 15:57 UTC. The Language team and Roan are trying to identify the root cause. It will be gradually reenabled once it's found and the issue gets fixed. [T163344]
- ORES Watchlist items appear duplicated. the ORES team is still investigating this. [T163337]
- codfw API database slaves overloaded and an additional one had to be pooled in in order to handle the load but it doesn't look like it was enough to fully alleviate this. The API is and has been available throughout this work, albeit with reduced performance. This is still being dealt with by the DBA team. [T163351]
- The IPs of the Redis servers used for locking was misconfigured in mediawiki-config, which resulted into file uploads (e.g. to Commons) and deletions to not work until it was manually fixed. This was not working between 14:30-14:44 UTC. [T163354]
The issues above are still being worked on and the situation is evolving, some some of the above may be inaccurate already. Phabricator is the authoritative place for both the root cause and mitigation action of all of those issues, with #codfw-rollout being the common tag.
Please follow-up there either on existing issues or new ones that you may discover over the course of the next 2-3 weeks :)
Thanks to everyone in and outside of ops for both the substantial amount of work that has gone into preparing for this day, as well as for all the firefighting for the better part of today. Expect to hear more from us when this project concludes.
Best, Faidon -- Faidon Liambotis Principal Operations Engineer Acting Director of Technical Operations Wikimedia Foundation
On Fri, Apr 07, 2017 at 04:58:09PM +0300, Faidon Liambotis wrote:
Hi all,
You may have heard already that, like last year, we are planning to switch our active datacenter from eqiad to codfw in the week of April 17th and back to eqiad two weeks later, on the week of May 1st. We do this periodically in order to exercise our ability to run from the backup site in case of a disaster, as well as our ability to switch seamlessly to it with little user impact.
Switching will be a gradual, multi-step process, the most visible step of which will be the switch of MediaWiki application servers and associated data stores. This will happen on April 19th (eqiad->codfw) and May 3rd (codfw->eqiad), both at 14:00 UTC. During those windows, the sites will be placed into read-only mode, for a period that we estimate to last approximately 20 to 30 minutes.
Furthermore, the deployment train will freeze for the weeks of April 17th and May 1st[1], but operate normally on the week of April 24th, in order to exercise our ability to deploy code while operating from the backup datacenter.
1: https://wikitech.wikimedia.org/wiki/Deployments
Compared to last year we have improved our processes considerably[2], in particular by making more services operate in an active/active manner, as well as by working on an automation and orchestration framework[3] to perform parallel executions across the fleet. The core of the MediaWiki switchover will be performed semi-automatically using a new software[4] that will execute all the necessary commands in sequence with little human involvement, and thus lowering the risk of introducing errors and delays.
2: https://wikitech.wikimedia.org/wiki/Switch_Datacenter 3: https://github.com/wikimedia/cumin 4: https://github.com/wikimedia/operations-switchdc
Improving and automating our processes means that we're not going to be following the exact same steps as last year. Because of that, and because of other changes introduced in our environment over the course of the year, there is a possibility of errors creeping into the process. We'll certainly try to fix any issues that arise during those weeks and we'd like to ask everyone to be on high-alert and vigilant.
To report any issues, please use one of the following channels:
- File a Phabricator issue with project #codfw-rollout
- Report issues on IRC: Freenode channel #wikimedia-tech (if urgent, or
during the migration) 3. Send an e-mail to the Operations list: ops@lists.wikimedia.org (any time)
Thanks, Faidon -- Faidon Liambotis Principal Operations Engineer Acting Director of Technical Operations Wikimedia Foundation