When: During a pre-defined DBA maintenance windows
Affected wikis:: https://noc.wikimedia.org/conf/highlight.php?file=dblists/s5.dblist
Checklist:
NEW primary: db2213
OLD primary: db2123
- Check configuration differences between new and old primary:
sudo pt-config-diff --defaults-file /root/.my.cnf h=db2123.codfw.wmnet h=db2213.codfw.wmnet
Failover prep:
- Silence alerts on all hosts:
sudo cookbook sre.hosts.downtime --hours 1 -r "Primary switchover s5 T374086" 'A:db-section-s5'
- Set NEW primary with weight 0
sudo dbctl instance db2213 set-weight 0 sudo dbctl config commit -m "Set db2213 with weight 0 T374086"
- Depool NEW from any specific group (API, vslow, dump) if present.
sudo dbctl instance db2213 edit # If some changes were made: sudo dbctl config commit -m "Remove db2213 from API/vslow/dump T374086"
- Topology changes, move all replicas under NEW primary
sudo db-switchover --timeout=25 --replicating-master --read-only-master --only-slave-move db2123 db2213
- Disable puppet on both nodes
sudo cumin 'db2123* or db2213*' 'disable-puppet "primary switchover T374086"'
- Merge gerrit puppet change to promote NEW primary: https://gerrit.wikimedia.org/r/1070870
Failover:
- Log the failover:
!log Starting s5 codfw failover from db2123 to db2213 - T374086
- Switch primaries:
sudo db-switchover --replicating-master --read-only-master --skip-slave-move db2123 db2213 echo "===== db2123 (OLD)"; sudo db-mysql db2123 -e 'show slave status\G' echo "===== db2213 (NEW)"; sudo db-mysql db2213 -e 'show slave status\G'
- Promote NEW primary in dbctl
sudo dbctl --scope codfw section s5 set-master db2213 sudo dbctl config commit -m "Promote db2213 to s5 primary T374086"
- Restart puppet on both hosts:
sudo cumin 'db2123* or db2213*' 'run-puppet-agent -e "primary switchover T374086"'
Clean up tasks:
- Clean up heartbeat table(s).
sudo db-mysql db2213 heartbeat -e "delete from heartbeat where file like 'db2123%';"
- 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 db2213 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 db2123
- Update candidate primary dbctl and orchestrator notes
sudo dbctl instance db2123 set-candidate-master --section s5 true sudo dbctl instance db2213 set-candidate-master --section s5 false sudo cumin 'dborch*' 'orchestrator-client -c untag -i db2213 --tag name=candidate' sudo cumin 'dborch*' 'orchestrator-client -c tag -i db2123 --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 = 's5';"
- (If needed): Depool db2123 for maintenance.
sudo dbctl instance db2123 depool sudo dbctl config commit -m "Depool db2123 T374086"
- Change db2123 weight to mimic the previous weight db2213:
sudo dbctl instance db2123 edit
- Apply outstanding schema changes to db2123 (if any)
- Update/resolve this ticket.