When: Anytime - no in use
Prerequisites: https://wikitech.wikimedia.org/wiki/MariaDB/Primary_switchover
Checklist:
NEW primary: es1037
OLD primary: es1038
- Check configuration differences between new and old primary:
sudo pt-config-diff --defaults-file /root/.my.cnf h=es1038.eqiad.wmnet h=es1037.eqiad.wmnet
Failover prep:
- Silence alerts on all hosts:
sudo cookbook sre.hosts.downtime --hours 1 -r "Primary switchover es6 T387273" 'A:db-section-es6'
- Set NEW primary with weight 0 (and depool it from API or vslow/dump groups if it is present).
sudo dbctl instance es1037 set-weight 0 sudo dbctl config commit -m "Set es1037 with weight 0 T387273"
- Topology changes, move all replicas under NEW primary
sudo db-switchover --read-only-master --replicating-master --timeout=25 --only-slave-move es1038 es1037
- Disable puppet on both nodes
sudo cumin 'es1038* or es1037*' 'disable-puppet "primary switchover T387273"'
- Merge gerrit puppet change to promote NEW primary: https://gerrit.wikimedia.org/r/1122894
Failover:
- Log the failover:
!log Starting es6 eqiad failover from es1038 to es1037 - T387273
- Switch primaries:
sudo db-switchover --read-only-master --replicating-master --skip-slave-move es1038 es1037 echo "===== es1038 (OLD)"; sudo db-mysql es1038 -e 'show slave status\G' echo "===== es1037 (NEW)"; sudo db-mysql es1037 -e 'show slave status\G'
- Promote NEW primary in dbctl, and remove read-only
sudo dbctl --scope eqiad section es6 set-master es1037 sudo dbctl --scope eqiad section es6 rw sudo dbctl config commit -m "Promote es1037 to es6 primary and set section read-write T387273"
- Clean up heartbeat table(s).
sudo db-mysql es1037 heartbeat -e "delete from heartbeat where file like 'es1038%';"
- Restart puppet on both hosts:
sudo cumin 'es1038* or es1037*' 'run-puppet-agent -e "primary switchover T387273"'
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 es1037 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 es1038
- Update candidate primary dbctl and orchestrator notes
sudo dbctl instance es1038 set-candidate-master --section es6 true sudo dbctl instance es1037 set-candidate-master --section es6 false sudo cumin 'dborch*' 'orchestrator-client -c untag -i es1037 --tag name=candidate' sudo cumin 'dborch*' 'orchestrator-client -c tag -i es1038 --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 = 'es6';"
- (If needed): Depool es1038 for maintenance.
sudo dbctl instance es1038 depool sudo dbctl config commit -m "Depool es1038 T387273"
- Change es1038 weight to mimic the previous weight es1037:
sudo dbctl instance es1038 edit
- Update/resolve this ticket.