When: Anytime - not in use for writes
- Prerequisites **: https://wikitech.wikimedia.org/wiki/MariaDB/Primary_switchover
Checklist:
NEW primary: es2021
OLD primary: es2020
- Check configuration differences between new and old primary:
sudo pt-config-diff --defaults-file /root/.my.cnf h=es2021.codfw.wmnet h=es2020.codfw.wmnet
Failover prep:
- Silence alerts on all hosts:
sudo cookbook sre.hosts.downtime --hours 1 -r "Primary switchover es4 T364451" 'A:db-section-es4'
- Set NEW primary with weight 0 (and depool it from API or vslow/dump groups if it is present).
sudo dbctl instance es2021 set-weight 0 sudo dbctl config commit -m "Set es2021 with weight 0 T364451"
- Topology changes, move all replicas under NEW primary
sudo db-switchover --read-only-master --replicating-master --timeout=25 --only-slave-move es2020 es2021
- Disable puppet on both nodes
sudo cumin 'es2021* or es2020*' 'disable-puppet "primary switchover T364451"'
- Merge gerrit puppet change to promote NEW primary: https://gerrit.wikimedia.org/r/c/operations/puppet/+/1029434
Failover:
- Log the failover:
!log Starting es4 codfw failover from es2020 to es2021 - T364451
- Switch primaries:
sudo db-switchover --read-only-master --replicating-master --skip-slave-move es2020 es2021 echo "===== es2020 (OLD)"; sudo db-mysql es2020 -e 'show slave status\G' echo "===== es2021 (NEW)"; sudo db-mysql es2021 -e 'show slave status\G'
- Promote NEW primary in dbctl, and remove read-only
sudo dbctl --scope codfw section es4 set-master es2021 sudo dbctl config commit -m "Promote es2021 to es4 primary and set section read-write T364451"
- Restart puppet on both hosts:
sudo cumin 'es2021* or es2020*' 'run-puppet-agent -e "primary switchover T364451"'
Clean up tasks:
- Clean up heartbeat table(s).
sudo db-mysql es2021 heartbeat -e "delete from heartbeat where file like 'es2020%';"
- change events for query killer:
events_coredb_master.sql on the new primary es2021 events_coredb_slave.sql on the new slave es2020
- Update candidate primary dbctl and orchestrator notes
sudo dbctl instance es2020 set-candidate-master --section es4 true sudo dbctl instance es2021 set-candidate-master --section es4 false (dborch1001): sudo orchestrator-client -c untag -i es2021 --tag name=candidate (dborch1001): sudo orchestrator-client -c tag -i es2020 --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 = 'es4';"
- (If needed): Depool es2020 for maintenance.
sudo dbctl instance es2020 depool sudo dbctl config commit -m "Depool es2020 T364451"
- Change es2021 weight to mimic the previous weight es2020:
sudo dbctl instance es2021 edit
- Update/resolve this ticket.