As part of upgrading s7 to debian buster/mariadb 10.4, we need to switch the primary to be db2121 (which is already running buster/10.4).
When: Wed 25th August at 06:00AM UTC.
Checklist:
- Create a task to communicate the chosen date and send an announcement to the community: T289130
NEW primary: db2121
OLD primary: db2118
- Check configuration differences between new and old primary:
sudo pt-config-diff --defaults-file /root/.my.cnf h=db2118.codfw.wmnet h=db2121.codfw.wmnet
Failover prep:
- Silence alerts on all hosts:
sudo cookbook sre.hosts.downtime --hours 1 -r "Primary switchover s7 T289129" 'A:db-section-s7'
- Set NEW primary with weight 0
sudo dbctl instance db2121 set-weight 0 sudo dbctl config commit -m "Set db2121 with weight 0 T289129"
- Topology changes, move all replicas under NEW primary
sudo db-switchover --timeout=15 --only-slave-move db2118 db2121
- Disable puppet on both nodes
sudo cumin 'db2118* or db2121*' 'disable-puppet "primary switchover T289129"'
- Merge gerrit puppet change to promote NEW primary: https://gerrit.wikimedia.org/r/c/operations/puppet/+/713625
Failover:
- Log the failover:
!log Starting s7 codfw failover from db2118 to db2121 - T289129
- Set section read-only:
sudo dbctl --scope codfw section s7 ro "Maintenance until 05:15 UTC - T289129" sudo dbctl config commit -m "Set s7 codfw as read-only for maintenance - T289129"
- Check s7 is indeed read-only
- Switch primaries:
sudo db-switchover --skip-slave-move db2118 db2121 echo "===== db2118 (OLD)"; sudo mysql.py -h db2118 -e 'show slave status\G' echo "===== db2121 (NEW)"; sudo mysql.py -h db2121 -e 'show slave status\G'
- Promote NEW primary in dbctl, and remove read-only
sudo dbctl --scope codfw section s7 set-master db2121 sudo dbctl --scope codfw section s7 rw sudo dbctl config commit -m "Promote db2121 to s7 primary and set section read-write T289129"
- Restart puppet on both hosts:
sudo cumin 'db2118* or db2121*' 'run-puppet-agent -e "primary switchover T289129"'
Clean up tasks:
- change events for query killer:
events_coredb_master.sql on the new primary db2121 events_coredb_slave.sql on the new slave db2118
- Update DNS: https://gerrit.wikimedia.org/r/c/operations/dns/+/713626
- Update candidate primary dbctl notes
sudo dbctl instance db2118 set-candidate-master --section s7 true sudo dbctl instance db2121 set-candidate-master --section s7 false
- Check tendril was updated
- Check zarcillo was updated
- db-switchover should do this. If it fails, do it manually: https://phabricator.wikimedia.org/P13956
- Depool OLD primary, as it's running 10.1, replicating from a 10.4 primary
sudo dbctl instance db2118 depool sudo dbctl config commit -m "Depool db2118 until it's reimaged to buster T289129"
- Downtime, and stop replication for OLD primary
- Apply outstanding schema changes to db2118 (if any)
- Update/resolve this ticket.