When: During a pre-defined DBA maintenance windows
Affected wikis:: https://noc.wikimedia.org/conf/highlight.php?file=dblists/s7.dblist
Checklist:
NEW primary: db1181
OLD primary: db1236
- Check configuration differences between new and old primary:
sudo pt-config-diff --defaults-file /root/.my.cnf h=db1236.eqiad.wmnet h=db1181.eqiad.wmnet
Failover prep:
- Silence alerts on all hosts:
sudo cookbook sre.hosts.downtime --hours 1 -r "Primary switchover s7 T416356" 'A:db-section-s7'
- Set NEW primary with weight 0
sudo dbctl instance db1181 set-weight 0 sudo dbctl config commit -m "Set db1181 with weight 0 T416356"
- Topology changes, move all replicas under NEW primary, open orchestartor to monitor the process and check it at the end.
sudo db-switchover --timeout=25 --replicating-master --read-only-master --only-slave-move db1236 db1181
- Disable puppet on both nodes
sudo cumin 'db1236* or db1181*' 'disable-puppet "primary switchover T416356"'
- Merge gerrit puppet change to promote NEW primary: https://gerrit.wikimedia.org/r/1236315
Failover:
- Log the failover:
!log Starting s7 eqiad failover from db1236 to db1181 - T416356
- Switch primaries:
sudo db-switchover --replicating-master --read-only-master --skip-slave-move db1236 db1181 echo "===== db1236 (OLD)"; sudo db-mysql db1236 -e 'show slave status\G' echo "===== db1181 (NEW)"; sudo db-mysql db1181 -e 'show slave status\G'
- Promote NEW primary in dbctl
sudo dbctl --scope eqiad section s7 set-master db1181 sudo dbctl config commit -m "Promote db1181 to s7 primary T416356"
- Clean up heartbeat table(s).
sudo db-mysql db1181 heartbeat -e "delete from heartbeat where file like 'db1236%';"
- Restart puppet on both hosts:
sudo cumin 'db1236* or db1181*' 'run-puppet-agent -e "primary switchover T416356"'
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 db1181 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 db1236
- Update candidate primary dbctl and orchestrator notes
sudo dbctl instance db1236 set-candidate-master --section s7 true sudo dbctl instance db1181 set-candidate-master --section s7 false sudo cumin 'dborch*' 'orchestrator-client -c untag -i db1181 --tag name=candidate' sudo cumin 'dborch*' 'orchestrator-client -c tag -i db1236 --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 = 's7';"
- Depool db1236 for maintenance.
sudo dbctl instance db1236 depool sudo dbctl config commit -m "Depool db1236 T416356"
- Change db1236 weight to mimic the previous weight db1181:
sudo dbctl instance db1236 edit
- Update/resolve this ticket.