When: During a pre-defined DBA maintenance windows
Affected wikis:: TO-DO
Checklist:
NEW primary: db1220
OLD primary: db1179
- Check configuration differences between new and old primary:
sudo pt-config-diff --defaults-file /root/.my.cnf h=db1179.eqiad.wmnet h=db1220.eqiad.wmnet
Failover prep:
- Silence alerts on all hosts:
sudo cookbook sre.hosts.downtime --hours 1 -r "Primary switchover x1 T359790" 'A:db-section-x1'
- Set NEW primary with weight 0 (and depool it from API or vslow/dump groups if it is present).
sudo dbctl instance db1220 set-weight 0 sudo dbctl config commit -m "Set db1220 with weight 0 T359790"
- Topology changes, move all replicas under NEW primary
sudo db-switchover --timeout=25 --replicating-master --read-only-master --only-slave-move db1179 db1220
- Disable puppet on both nodes
sudo cumin 'db1179* or db1220*' 'disable-puppet "primary switchover T359790"'
- Merge gerrit puppet change to promote NEW primary: FIXME
Failover:
- Log the failover:
!log Starting x1 eqiad failover from db1179 to db1220 - T359790
- Switch primaries:
sudo db-switchover --replicating-master --read-only-master --skip-slave-move db1179 db1220 echo "===== db1179 (OLD)"; sudo db-mysql db1179 -e 'show slave status\G' echo "===== db1220 (NEW)"; sudo db-mysql db1220 -e 'show slave status\G'
- Promote NEW primary in dbctl
sudo dbctl --scope eqiad section x1 set-master db1220 sudo dbctl config commit -m "Promote db1220 to x1 primary T359790"
- Restart puppet on both hosts:
sudo cumin 'db1179* or db1220*' 'run-puppet-agent -e "primary switchover T359790"'
Clean up tasks:
- Clean up heartbeat table(s).
sudo db-mysql db1220 heartbeat -e "delete from heartbeat where file like 'db1179%';"
- change events for query killer:
events_coredb_master.sql on the new primary db1220 events_coredb_slave.sql on the new slave db1179
- Update candidate primary dbctl and orchestrator notes
sudo dbctl instance db1179 set-candidate-master --section x1 true sudo dbctl instance db1220 set-candidate-master --section x1 false (dborch1001): sudo orchestrator-client -c untag -i db1220 --tag name=candidate (dborch1001): sudo orchestrator-client -c tag -i db1179 --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 = 'x1';"
- (If needed): Depool db1179 for maintenance.
sudo dbctl instance db1179 depool sudo dbctl config commit -m "Depool db1179 T359790"
- Change db1179 weight to mimic the previous weight db1220:
sudo dbctl instance db1179 edit
- Apply outstanding schema changes to db1179 (if any)
- Update/resolve this ticket.