Eqiad Migration Planning

Revision as of 00:17, 22 December 2012

Coordination

• We now have an incomplete tracking ticket in RT that depends on more specific tickets.
• Platform Engineering will be using Bug 39106 for tracking dev tasks
• Sept 12 Update - http://etherpad.wikimedia.org/TechOps-12Sept2012
• Weekly Countdown meeting http://etherpad.wmflabs.org/pad/p/EqiadMigration - meeting minutes

Risk & Mitigation

Identify the high risk migration tasks and ensure we have a way to mitigate or revert without extended downtime.

• What could cause fallback to Tampa a big problem should migration failed?
  • should Ceph fail?
  • should Swift@Tampa fail?

Outstanding Server/System Readiness

• App, Imagescalers, Bits, Jobrunners and API Apaches
  • Image scalers: Ready to deploy @ Eqiad - PY
  • Apache/API: Ready to deploy @ Eqiad (mw1017-mw1019 puppetized for deploy testing) - PY
  • Ready to test deploy @ Eqiad - PY

• Deployment system
  • using Git-deploy & ready for testing @ EQIAD - RyanLane, PY and ChrisM
    • need to change apache and mw cfg - (AI - tbd/RobLa)
    • Need to identify / doc test requirements and success criteria (what are the use cases?) - CM/PY
    • Chris M will work with Ops (PY lead guy) on setting up the tests
      • Overview of existing UI tests: https://github.com/wikimedia/qa-browsertests/tree/master/features

• Swift in Tampa & Ceph in EQIAD
  • Current plan is to have Ceph running at Eqiad (final decision - end of Dec by Mark/Faidon)
  • Swift @ Tampa is in production already
  • servers online; needs cluster replication enabled - netapp replication enabled
  • Still need to migrate Math, Captcha, Misc objects from ms7 to Swift - Aaron
  • Might have to run Swift and ImageScalers in Tampa while the rest of the stack are running in Eqiad
  • Aaron to test performance lag
  • Ceph update
    • overcame several issues/ steep learning curve; cluster more stable
    • currrently performing stability & stress tests
    • Servers are being provisioned - Faidon
    • MW multiwrite for thumbs - Aaron/Mark to discuss details (already happening with NAS)

• Memcached servers
  • mc01 - mc16 (Tampa) in production - done
  • mc1001-mc1016 OS installed, ready for puppet to be run.
  • Decided to use Redis and use MW multi-write feature to write to both existing MC and the new MC servers, then enable Redis replication from Tampa to Eqiad

• Parser Cache servers
  • servers are provisioned; awaiting parser cache sharding - Asher/Tim

• Databases
  • servers and replication - ready for switchover
  • Grants needed (SQL )

• Poolcounter
  • Done: helium and potassium are installed and puppetized
• Netapp
  • /home/wikipedia for deployments (prolly not using it; use git-deploy)
  • /home - completed in Tampa, not strictly necessary in eqiad

• Deployment server (fenari's deployment support infrastructure part, misc::deployment etc)
  • done. server name is Tin
  • This might not be needed if we are using git-deploy

• Hume equivalent (misc::maintenance) - postponed

• Application logging server - for mediawiki wmerrors + apache syslog
  • eqiad version of the udp2log instance on nfs1 that writes to /home/w/logs
  • Done: server 'flourine' for apache logs

• Setup and Deploy parsoid servers @ Eqiad

• Upload Varnish - done

Software / Config Requirements

• MediaWiki deploy support for per colo config variances (Bugzilla 39082)
  • generating eqiad and pmtpa dsh groups
  • mostly done - rolling out by end of month https://gerrit.wikimedia.org/r/#/c/32167/ https://gerrit.wikimedia.org/r/#/c/32168/ ..
  • new mediawiki conf files for eqiad

• replicating the git checkouts, etc. to new /home
  • not an issue

Actually Failing Over

• deploy db.php with all shards set to read-only in both pmtpa and eqiad
• deploy squid and mobile + bits varnish configs pointing to eqiad apaches
• master swap every core db and writable es shard to eqiad
• deploy db.php in eqiad removing the read-only flag, leave it read-only in pmtpa
  • the above master-swap + db.php deploys can be done shard by shard to limit the time certain projects are read-only
• dns changes - our current steady state is to point wikipedia-lb.wikimedia.org in the US to eqiad but future scenarios may include external dns switches.
• Swift replication reversal - from Eqiad to Tampa
• Rollback plan - needs to add details

Improving Failover

• pre-generate squid + varnish configs for different primary datacenter roles
• implement MHA to better automate the mysql master failovers
• migrate session storage to redis, with redundant replicas across colos

See more

• Records and original tracking doc - http://etherpad.wikimedia.org/EQIAD-rollout-sequence
• Category:Eqiad cluster

Parking Lot Issues

• Identify and plan around the deployment/migration date - tentatively Oct 15, 2012 [see below]. Need to communicate date.
  • Migration needs to happen before Fundraising season starts in Nov.
  • Vacation 'freeze'; all hands on deck week before and after deployment
    • Why? Not every person is vital to migration. --second. if you're not vital to migration, this seems like overkill - who are u pls?
  • migrate ns1 from tampa to ashburn, but not a critical item.

• An update from CT Woo from October 2012 regarding the status of the migration is available here. It looks like it'll be pushed back to January or February 2013 (post-annual fundraiser).