When: During a pre-defined DBA maintenance windows
Affected wikis:: https://noc.wikimedia.org/conf/highlight.php?file=dblists/s2.dblist
Checklist:
NEW primary: db1162
OLD primary: db1222
- Check configuration differences between new and old primary:
sudo pt-config-diff --defaults-file /root/.my.cnf h=db1222.eqiad.wmnet h=db1162.eqiad.wmnet
Failover prep:
- Silence alerts on all hosts:
sudo cookbook sre.hosts.downtime --hours 1 -r "Primary switchover s2 T384597" 'A:db-section-s2'
- Set NEW primary with weight 0
sudo dbctl instance db1162 set-weight 0 sudo dbctl config commit -m "Set db1162 with weight 0 T384597"
- Depool NEW from any specific group (API, vslow, dump) if present.
sudo dbctl instance db1162 edit # If some changes were made: sudo dbctl config commit -m "Remove db1162 from API/vslow/dump T384597"
- Topology changes, move all replicas under NEW primary
sudo db-switchover --timeout=25 --replicating-master --read-only-master --only-slave-move db1222 db1162
- Disable puppet on both nodes
sudo cumin 'db1222* or db1162*' 'disable-puppet "primary switchover T384597"'
- Merge gerrit puppet change to promote NEW primary: https://gerrit.wikimedia.org/r/1113802
Failover:
- Log the failover:
!log Starting s2 eqiad failover from db1222 to db1162 - T384597
- Switch primaries:
sudo db-switchover --replicating-master --read-only-master --skip-slave-move db1222 db1162 echo "===== db1222 (OLD)"; sudo db-mysql db1222 -e 'show slave status\G' echo "===== db1162 (NEW)"; sudo db-mysql db1162 -e 'show slave status\G'
- Promote NEW primary in dbctl
sudo dbctl --scope eqiad section s2 set-master db1162 sudo dbctl config commit -m "Promote db1162 to s2 primary T384597"
- Clean up heartbeat table(s).
sudo db-mysql db1162 heartbeat -e "delete from heartbeat where file like 'db1222%';"
- Restart puppet on both hosts:
sudo cumin 'db1222* or db1162*' 'run-puppet-agent -e "primary switchover T384597"'
Clean up tasks:
- change events for query killer:
curl -sS 'https://gerrit.wikimedia.org/r/plugins/gitiles/operations/software/+/refs/heads/master/dbtools/events_coredb_master.sql?format=TEXT' | base64 -d | sudo db-mysql db1162 curl -sS 'https://gerrit.wikimedia.org/r/plugins/gitiles/operations/software/+/refs/heads/master/dbtools/events_coredb_slave.sql?format=TEXT' | base64 -d | sudo db-mysql db1222
- Update candidate primary dbctl and orchestrator notes
sudo dbctl instance db1222 set-candidate-master --section s2 true sudo dbctl instance db1162 set-candidate-master --section s2 false sudo cumin 'dborch*' 'orchestrator-client -c untag -i db1162 --tag name=candidate' sudo cumin 'dborch*' 'orchestrator-client -c tag -i db1222 --tag name=candidate'
- Check zarcillo was updated
- db-switchover should do this. If it fails, do it manually: https://phabricator.wikimedia.org/P13956
sudo db-mysql db1215 zarcillo -e "select * from masters where section = 's2';"
- (If needed): Depool db1222 for maintenance.
sudo dbctl instance db1222 depool sudo dbctl config commit -m "Depool db1222 T384597"
- Change db1222 weight to mimic the previous weight db1162:
sudo dbctl instance db1222 edit
- Update/resolve this ticket.