When: During a pre-defined DBA maintenance windows
Affected wikis:: https://noc.wikimedia.org/conf/highlight.php?file=dblists/s2.dblist
Checklist:
NEW primary: db2204
OLD primary: db2207
- Check configuration differences between new and old primary:
sudo pt-config-diff --defaults-file /root/.my.cnf h=db2207.codfw.wmnet h=db2204.codfw.wmnet
Failover prep:
- Silence alerts on all hosts:
sudo cookbook sre.hosts.downtime --hours 1 -r "Primary switchover s2 T366241" 'A:db-section-s2'
- Set NEW primary with weight 0
sudo dbctl instance db2204 set-weight 0 sudo dbctl config commit -m "Set db2204 with weight 0 T366241"
- Depool NEW from any specific group (API, vslow, dump) if present.
sudo dbctl instance db2204 edit # If some changes were made: sudo dbctl config commit -m "Remove db2204 from API/vslow/dump T366241"
- Topology changes, move all replicas under NEW primary
sudo db-switchover --timeout=25 --replicating-master --read-only-master --only-slave-move db2207 db2204
- Disable puppet on both nodes
sudo cumin 'db2207* or db2204*' 'disable-puppet "primary switchover T366241"'
- Merge gerrit puppet change to promote NEW primary: FIXME
Failover:
- Log the failover:
!log Starting s2 codfw failover from db2207 to db2204 - T366241
- Switch primaries:
sudo db-switchover --replicating-master --read-only-master --skip-slave-move db2207 db2204 echo "===== db2207 (OLD)"; sudo db-mysql db2207 -e 'show slave status\G' echo "===== db2204 (NEW)"; sudo db-mysql db2204 -e 'show slave status\G'
- Promote NEW primary in dbctl
sudo dbctl --scope codfw section s2 set-master db2204 sudo dbctl config commit -m "Promote db2204 to s2 primary T366241"
- Restart puppet on both hosts:
sudo cumin 'db2207* or db2204*' 'run-puppet-agent -e "primary switchover T366241"'
Clean up tasks:
- Clean up heartbeat table(s).
sudo db-mysql db2204 heartbeat -e "delete from heartbeat where file like 'db2207%';"
- change events for query killer:
events_coredb_master.sql on the new primary db2204 events_coredb_slave.sql on the new slave db2207
- Update candidate primary dbctl and orchestrator notes
sudo dbctl instance db2207 set-candidate-master --section s2 true sudo dbctl instance db2204 set-candidate-master --section s2 false (dborch1001): sudo orchestrator-client -c untag -i db2204 --tag name=candidate (dborch1001): sudo orchestrator-client -c tag -i db2207 --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 db2207 for maintenance.
sudo dbctl instance db2207 depool sudo dbctl config commit -m "Depool db2207 T366241"
- Change db2207 weight to mimic the previous weight db2204:
sudo dbctl instance db2207 edit
- Apply outstanding schema changes to db2207 (if any)
- Update/resolve this ticket.