When: Anytime
- Prerequisites **: https://wikitech.wikimedia.org/wiki/MariaDB/Primary_switchover
Checklist:
NEW primary: db2112
OLD primary: db2103
- Check configuration differences between new and old primary:
sudo pt-config-diff --defaults-file /root/.my.cnf h=db2103.codfw.wmnet h=db2112.codfw.wmnet
Failover prep:
- Silence alerts on all hosts:
sudo cookbook sre.hosts.downtime --hours 1 -r "Primary switchover s1 T317614" 'A:db-section-s1'
- Set NEW primary with weight 0 (and depool it from API or vslow/dump groups if it is present).
sudo dbctl instance db2112 set-weight 0 sudo dbctl config commit -m "Set db2112 with weight 0 T317614"
- Topology changes, move all replicas under NEW primary
sudo db-switchover --replicating-master --read-only-master --timeout=25 --only-slave-move db2103 db2112
- Disable puppet on both nodes
sudo cumin 'db2103* or db2112*' 'disable-puppet "primary switchover T317614"'
- Merge gerrit puppet change to promote NEW primary: https://gerrit.wikimedia.org/r/c/operations/puppet/+/831814/
Failover:
- Log the failover:
!log Starting s1 codfw failover from db2103 to db2112 - T317614
- Switch primaries:
sudo db-switchover --replicating-master --read-only-master --skip-slave-move db2103 db2112 echo "===== db2103 (OLD)"; sudo db-mysql db2103 -e 'show slave status\G' echo "===== db2112 (NEW)"; sudo db-mysql db2112 -e 'show slave status\G'
- Promote NEW primary in dbctl, and remove read-only
sudo dbctl --scope codfw section s1 set-master db2112 sudo dbctl config commit -m "Promote db2112 to s1 primary T317614"
- Restart puppet on both hosts:
sudo cumin 'db2103* or db2112*' 'run-puppet-agent -e "primary switchover T317614"'
Clean up tasks:
- Clean up heartbeat table(s).
sudo db-mysql db2112 heartbeat -e "delete from heartbeat where file like 'db2103%';"
- change events for query killer:
events_coredb_master.sql on the new primary db2112 events_coredb_slave.sql on the new slave db2103
- Update candidate primary dbctl and orchestrator notes
sudo dbctl instance db2103 set-candidate-master --section s1 true sudo dbctl instance db2112 set-candidate-master --section s1 false (dborch1001): sudo orchestrator-client -c untag -i db2112 --tag name=candidate (dborch1001): sudo orchestrator-client -c tag -i db2103 --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 = 's1';"
- (If needed): Depool db2103 for maintenance.
sudo dbctl instance db2103 depool sudo dbctl config commit -m "Depool db2103 T317614"
- Change db2103 weight to mimic the previous weight db2112:
sudo dbctl instance db2103 edit
- Apply outstanding schema changes to db2103 (if any): Will be tracked in their own task
- Update/resolve this ticket.