When: During a pre-defined DBA maintenance windows
Affected wikis:: https://noc.wikimedia.org/conf/highlight.php?file=dblists/s3.dblist
Checklist:
NEW primary: db1223
OLD primary: db1189
- Check configuration differences between new and old primary:
sudo pt-config-diff --defaults-file /root/.my.cnf h=db1189.eqiad.wmnet h=db1223.eqiad.wmnet
Failover prep:
- Silence alerts on all hosts:
sudo cookbook sre.hosts.downtime --hours 1 -r "Primary switchover s3 T385160" 'A:db-section-s3'
- Set NEW primary with weight 0
sudo dbctl instance db1223 set-weight 0 sudo dbctl config commit -m "Set db1223 with weight 0 T385160"
- Depool NEW from any specific group (API, vslow, dump) if present.
sudo dbctl instance db1223 edit # If some changes were made: sudo dbctl config commit -m "Remove db1223 from API/vslow/dump T385160"
- Topology changes, move all replicas under NEW primary
sudo db-switchover --timeout=25 --replicating-master --read-only-master --only-slave-move db1189 db1223
- Disable puppet on both nodes
sudo cumin 'db1189* or db1223*' 'disable-puppet "primary switchover T385160"'
- Merge gerrit puppet change to promote NEW primary: FIXME
Failover:
- Log the failover:
!log Starting s3 eqiad failover from db1189 to db1223 - T385160
- Switch primaries:
sudo db-switchover --replicating-master --read-only-master --skip-slave-move db1189 db1223 echo "===== db1189 (OLD)"; sudo db-mysql db1189 -e 'show slave status\G' echo "===== db1223 (NEW)"; sudo db-mysql db1223 -e 'show slave status\G'
- Promote NEW primary in dbctl
sudo dbctl --scope eqiad section s3 set-master db1223 sudo dbctl config commit -m "Promote db1223 to s3 primary T385160"
- Clean up heartbeat table(s).
sudo db-mysql db1223 heartbeat -e "delete from heartbeat where file like 'db1189%';"
- Restart puppet on both hosts:
sudo cumin 'db1189* or db1223*' 'run-puppet-agent -e "primary switchover T385160"'
Clean up tasks:
- 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 db1223 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 db1189
- Update candidate primary dbctl and orchestrator notes
sudo dbctl instance db1189 set-candidate-master --section s3 true sudo dbctl instance db1223 set-candidate-master --section s3 false sudo cumin 'dborch*' 'orchestrator-client -c untag -i db1223 --tag name=candidate' sudo cumin 'dborch*' 'orchestrator-client -c tag -i db1189 --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 = 's3';"
- (If needed): Depool db1189 for maintenance.
sudo dbctl instance db1189 depool sudo dbctl config commit -m "Depool db1189 T385160"
- Change db1189 weight to mimic the previous weight db1223:
sudo dbctl instance db1189 edit
- Apply outstanding schema changes to db1189 (if any)
- Update/resolve this ticket.