When: During a pre-defined DBA maintenance windows
Affected wikis:: https://noc.wikimedia.org/conf/highlight.php?file=dblists/s5.dblist
Checklist:
NEW primary: db1130
OLD primary: db1100
- Check configuration differences between new and old primary:
sudo pt-config-diff --defaults-file /root/.my.cnf h=db1100.eqiad.wmnet h=db1130.eqiad.wmnet
Failover prep:
- Silence alerts on all hosts:
sudo cookbook sre.hosts.downtime --hours 1 -r "Primary switchover s5 T333479" 'A:db-section-s5'
- Set NEW primary with weight 0 (and depool it from API or vslow/dump groups if it is present).
sudo dbctl instance db1130 set-weight 0 sudo dbctl config commit -m "Set db1130 with weight 0 T333479"
- Topology changes, move all replicas under NEW primary
sudo db-switchover --timeout=25 --replicating-master --read-only-master --only-slave-move db1100 db1130
- Disable puppet on both nodes
sudo cumin 'db1100* or db1130*' 'disable-puppet "primary switchover T333479"'
- Merge gerrit puppet change to promote NEW primary: FIXME
Failover:
- Log the failover:
!log Starting s5 eqiad failover from db1100 to db1130 - T333479
- Switch primaries:
sudo db-switchover --replicating-master --read-only-master --skip-slave-move db1100 db1130 echo "===== db1100 (OLD)"; sudo db-mysql db1100 -e 'show slave status\G' echo "===== db1130 (NEW)"; sudo db-mysql db1130 -e 'show slave status\G'
- Promote NEW primary in dbctl
sudo dbctl --scope eqiad section s5 set-master db1130 sudo dbctl config commit -m "Promote db1130 to s5 primary T333479"
- Restart puppet on both hosts:
sudo cumin 'db1100* or db1130*' 'run-puppet-agent -e "primary switchover T333479"'
Clean up tasks:
- Clean up heartbeat table(s).
sudo db-mysql db1130 heartbeat -e "delete from heartbeat where file like 'db1100%';"
- change events for query killer:
events_coredb_master.sql on the new primary db1130 events_coredb_slave.sql on the new slave db1100
- Update candidate primary dbctl and orchestrator notes
sudo dbctl instance db1100 set-candidate-master --section s5 true sudo dbctl instance db1130 set-candidate-master --section s5 false (dborch1001): sudo orchestrator-client -c untag -i db1130 --tag name=candidate (dborch1001): sudo orchestrator-client -c tag -i db1100 --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 db1115 zarcillo -e "select * from masters where section = 's5';"
- (If needed): Depool db1100 for maintenance.
sudo dbctl instance db1100 depool sudo dbctl config commit -m "Depool db1100 T333479"
- Change db1100 weight to mimic the previous weight db1130:
sudo dbctl instance db1100 edit
- Apply outstanding schema changes to db1100 (if any)
- Update/resolve this ticket.