When: During a pre-defined DBA maintenance windows
Affected wikis:: https://noc.wikimedia.org/conf/highlight.php?file=dblists/s6.dblist
Checklist:
NEW primary: db2214
OLD primary: db2129
- Check configuration differences between new and old primary:
sudo pt-config-diff --defaults-file /root/.my.cnf h=db2129.codfw.wmnet h=db2214.codfw.wmnet
Failover prep:
- Silence alerts on all hosts:
sudo cookbook sre.hosts.downtime --hours 1 -r "Primary switchover s6 T374087" 'A:db-section-s6'
- Set NEW primary with weight 0
sudo dbctl instance db2214 set-weight 0 sudo dbctl config commit -m "Set db2214 with weight 0 T374087"
- Depool NEW from any specific group (API, vslow, dump) if present.
sudo dbctl instance db2214 edit # If some changes were made: sudo dbctl config commit -m "Remove db2214 from API/vslow/dump T374087"
- Topology changes, move all replicas under NEW primary
sudo db-switchover --timeout=25 --replicating-master --read-only-master --only-slave-move db2129 db2214
- Disable puppet on both nodes
sudo cumin 'db2129* or db2214*' 'disable-puppet "primary switchover T374087"'
- Merge gerrit puppet change to promote NEW primary: FIXME
Failover:
- Log the failover:
!log Starting s6 codfw failover from db2129 to db2214 - T374087
- Switch primaries:
sudo db-switchover --replicating-master --read-only-master --skip-slave-move db2129 db2214 echo "===== db2129 (OLD)"; sudo db-mysql db2129 -e 'show slave status\G' echo "===== db2214 (NEW)"; sudo db-mysql db2214 -e 'show slave status\G'
- Promote NEW primary in dbctl
sudo dbctl --scope codfw section s6 set-master db2214 sudo dbctl config commit -m "Promote db2214 to s6 primary T374087"
- Restart puppet on both hosts:
sudo cumin 'db2129* or db2214*' 'run-puppet-agent -e "primary switchover T374087"'
Clean up tasks:
- Clean up heartbeat table(s).
sudo db-mysql db2214 heartbeat -e "delete from heartbeat where file like 'db2129%';"
- 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 db2214 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 db2129
- Update candidate primary dbctl and orchestrator notes
sudo dbctl instance db2129 set-candidate-master --section s6 true sudo dbctl instance db2214 set-candidate-master --section s6 false sudo cumin 'dborch*' 'orchestrator-client -c untag -i db2214 --tag name=candidate' sudo cumin 'dborch*' 'orchestrator-client -c tag -i db2129 --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 = 's6';"
- (If needed): Depool db2129 for maintenance.
sudo dbctl instance db2129 depool sudo dbctl config commit -m "Depool db2129 T374087"
- Change db2129 weight to mimic the previous weight db2214:
sudo dbctl instance db2129 edit
- Apply outstanding schema changes to db2129 (if any)
- Update/resolve this ticket.