When: During a pre-defined DBA maintenance windows
Affected wikis:: https://noc.wikimedia.org/conf/highlight.php?file=dblists/s1.dblist
Checklist:
NEW primary: db2212
OLD primary: db2203
- Check configuration differences between new and old primary:
sudo pt-config-diff --defaults-file /root/.my.cnf h=db2203.codfw.wmnet h=db2212.codfw.wmnet
Failover prep:
- Silence alerts on all hosts:
sudo cookbook sre.hosts.downtime --hours 1 -r "Primary switchover s1 T366552" 'A:db-section-s1'
- Set NEW primary with weight 0
sudo dbctl instance db2212 set-weight 0 sudo dbctl config commit -m "Set db2212 with weight 0 T366552"
- Depool NEW from any specific group (API, vslow, dump) if present.
sudo dbctl instance db2212 edit # If some changes were made: sudo dbctl config commit -m "Remove db2212 from API/vslow/dump T366552"
- Topology changes, move all replicas under NEW primary
sudo db-switchover --timeout=25 --replicating-master --read-only-master --only-slave-move db2203 db2212
- Disable puppet on both nodes
sudo cumin 'db2203* or db2212*' 'disable-puppet "primary switchover T366552"'
- Merge gerrit puppet change to promote NEW primary: https://gerrit.wikimedia.org/r/c/operations/puppet/+/1038351
Failover:
- Log the failover:
!log Starting s1 codfw failover from db2203 to db2212 - T366552
- Switch primaries:
sudo db-switchover --replicating-master --read-only-master --skip-slave-move db2203 db2212 echo "===== db2203 (OLD)"; sudo db-mysql db2203 -e 'show slave status\G' echo "===== db2212 (NEW)"; sudo db-mysql db2212 -e 'show slave status\G'
- Promote NEW primary in dbctl
sudo dbctl --scope codfw section s1 set-master db2212 sudo dbctl config commit -m "Promote db2212 to s1 primary T366552"
- Restart puppet on both hosts:
sudo cumin 'db2203* or db2212*' 'run-puppet-agent -e "primary switchover T366552"'
Clean up tasks:
- Clean up heartbeat table(s).
sudo db-mysql db2212 heartbeat -e "delete from heartbeat where file like 'db2203%';"
- change events for query killer:
events_coredb_master.sql on the new primary db2212 events_coredb_slave.sql on the new slave db2203
- Update candidate primary dbctl and orchestrator notes
sudo dbctl instance db2203 set-candidate-master --section s1 true sudo dbctl instance db2212 set-candidate-master --section s1 false (dborch1001): sudo orchestrator-client -c untag -i db2212 --tag name=candidate (dborch1001): sudo orchestrator-client -c tag -i db2203 --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 = 's1';"
- (If needed): Depool db2203 for maintenance.
sudo dbctl instance db2203 depool sudo dbctl config commit -m "Depool db2203 T366552"
- Change db2203 weight to mimic the previous weight db2212:
sudo dbctl instance db2203 edit
- Apply outstanding schema changes to db2203 (if any)
- Update/resolve this ticket.