When: During a pre-defined DBA maintenance windows
Affected wikis:: https://noc.wikimedia.org/conf/highlight.php?file=dblists/s6.dblist
Checklist:
NEW primary: db1173
OLD primary: db1201
- Check configuration differences between new and old primary:
sudo pt-config-diff --defaults-file /root/.my.cnf h=db1201.eqiad.wmnet h=db1173.eqiad.wmnet
Failover prep:
- Silence alerts on all hosts:
sudo cookbook sre.hosts.downtime --hours 1 -r "Primary switchover s6 T387433" 'A:db-section-s6'
- Set NEW primary with weight 0
sudo dbctl instance db1173 set-weight 0 sudo dbctl config commit -m "Set db1173 with weight 0 T387433"
- Depool NEW from any specific group (API, vslow, dump) if present.
sudo dbctl instance db1173 edit # If some changes were made: sudo dbctl config commit -m "Remove db1173 from API/vslow/dump T387433"
- Topology changes, move all replicas under NEW primary
sudo db-switchover --timeout=25 --replicating-master --read-only-master --only-slave-move db1201 db1173
- Disable puppet on both nodes
sudo cumin 'db1201* or db1173*' 'disable-puppet "primary switchover T387433"'
- Merge gerrit puppet change to promote NEW primary: https://gerrit.wikimedia.org/r/1123276
Failover:
- Log the failover:
!log Starting s6 eqiad failover from db1201 to db1173 - T387433
- Switch primaries:
sudo db-switchover --replicating-master --read-only-master --skip-slave-move db1201 db1173 echo "===== db1201 (OLD)"; sudo db-mysql db1201 -e 'show slave status\G' echo "===== db1173 (NEW)"; sudo db-mysql db1173 -e 'show slave status\G'
- Promote NEW primary in dbctl
sudo dbctl --scope eqiad section s6 set-master db1173 sudo dbctl config commit -m "Promote db1173 to s6 primary T387433"
- Clean up heartbeat table(s).
sudo db-mysql db1173 heartbeat -e "delete from heartbeat where file like 'db1201%';"
- Restart puppet on both hosts:
sudo cumin 'db1201* or db1173*' 'run-puppet-agent -e "primary switchover T387433"'
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 db1173 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 db1201
- Update candidate primary dbctl and orchestrator notes
sudo dbctl instance db1201 set-candidate-master --section s6 true sudo dbctl instance db1173 set-candidate-master --section s6 false sudo cumin 'dborch*' 'orchestrator-client -c untag -i db1173 --tag name=candidate' sudo cumin 'dborch*' 'orchestrator-client -c tag -i db1201 --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 = 's6';"
- (If needed): Depool db1201 for maintenance.
sudo dbctl instance db1201 depool sudo dbctl config commit -m "Depool db1201 T387433"
- Change db1201 weight to mimic the previous weight db1173:
sudo dbctl instance db1201 edit
- Update/resolve this ticket.