When: Anytime, DC switch only.
- Prerequisites **: https://wikitech.wikimedia.org/wiki/MariaDB/Primary_switchover
Checklist:
NEW primary: db2115
OLD primary: db2096
- Check that db2115 is running STATEMENT and the latest kernel
- The STATEMENT part is covered by https://gerrit.wikimedia.org/r/c/operations/puppet/+/827491
- Check configuration differences between new and old primary:
sudo pt-config-diff --defaults-file /root/.my.cnf h=db2096.codfw.wmnet h=db2115.codfw.wmnet
Failover prep:
- Silence alerts on all hosts:
sudo cookbook sre.hosts.downtime --hours 1 -r "DC switchover x1 T316522" '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 db2115 set-weight 0 sudo dbctl config commit -m "Set db2115 with weight 0 T316522"
- Topology changes, move all replicas under NEW primary
sudo db-switchover --read-only-master --replicating-master --read-only-master --timeout=25 --only-slave-move db2096 db2115
- Disable puppet on both nodes
sudo cumin 'db2096* or db2115*' 'disable-puppet "primary switchover T316522"'
- Merge gerrit puppet change to promote NEW primary: https://gerrit.wikimedia.org/r/c/operations/puppet/+/827864
Failover:
- Log the failover:
!log Starting x1 codfw failover from db2096 to db2115 - T316522
- Switch primaries:
sudo db-switchover --replicating-master --read-only-master --skip-slave-move db2096 db2115 echo "===== db2096 (OLD)"; sudo db-mysql db2096 -e 'show slave status\G' echo "===== db2115 (NEW)"; sudo db-mysql db2115 -e 'show slave status\G'
- Promote NEW primary in dbctl, and remove read-only
sudo dbctl --scope codfw section x1 set-master db2115 sudo dbctl config commit -m "Promote db2115 to x1 codfw primary T316522"
- Restart puppet on both hosts:
sudo cumin 'db2096* or db2115*' 'run-puppet-agent -e "primary switchover T316522"'
Clean up tasks:
- Clean up heartbeat table(s).
sudo db-mysql db2115 heartbeat -e "delete from heartbeat where file like 'db2096%';"
- change events for query killer:
events_coredb_master.sql on the new primary db2115 events_coredb_slave.sql on the new slave db2096
- Update candidate primary dbctl and orchestrator notes
sudo dbctl instance db2096 set-candidate-master --section x1 true sudo dbctl instance db2115 set-candidate-master --section x1 false (dborch1001): sudo orchestrator-client -c untag -i db2115 --tag name=candidate (dborch1001): sudo orchestrator-client -c tag -i db2096 --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 = 'x1';"
- (If needed): Depool db2096 for maintenance.
sudo dbctl instance db2096 depool sudo dbctl config commit -m "Depool db2096 T316522"
- Change db2096 weight to mimic the previous weight db2115:
sudo dbctl instance db2096 edit
- Apply outstanding schema changes to db2096 (if any) -> To be tracked on their own tasks.
- Update/resolve this ticket.