When: During a pre-defined DBA maintenance windows
Affected wikis:: https://noc.wikimedia.org/conf/highlight.php?file=dblists/s5.dblist
Checklist:
NEW primary: db1183
OLD primary: db1230
- Check configuration differences between new and old primary:
sudo pt-config-diff --defaults-file /root/.my.cnf h=db1230.eqiad.wmnet h=db1183.eqiad.wmnet 17 config differences Variable db1230 db1183 ========================= ========================= ========================= general_log_file db1230.log db1183.log gtid_binlog_pos 171970778-171970778-63... 171970593-171970593-24... gtid_binlog_state 171970778-171970778-63... 171970593-171970593-24... gtid_current_pos 0-180359179-5734605861... 0-180359179-5734605861... gtid_domain_id 171974710 171970778 gtid_slave_pos 0-180359179-5734605861... 0-180359179-5734605861... hostname db1230 db1183 innodb_buffer_pool_size 405874409472 404800667648 log_bin_basename /srv/sqldata/db1230-bin /srv/sqldata/db1183-bin log_bin_index /srv/sqldata/db1230-bi... /srv/sqldata/db1183-bi... pid_file /srv/sqldata/db1230.pid /srv/sqldata/db1183.pid report_host db1230.eqiad.wmnet db1183.eqiad.wmnet rpl_semi_sync_master_e... ON OFF rpl_semi_sync_slave_en... OFF ON server_id 171974710 171970778 slow_query_log_file db1230-slow.log db1183-slow.log wsrep_node_name db1230 db1183
Failover prep:
- Silence alerts on all hosts:
sudo cookbook sre.hosts.downtime --hours 1 -r "Primary switchover s5 T376867" 'A:db-section-s5'
- Set NEW primary with weight 0
sudo dbctl instance db1183 set-weight 0 sudo dbctl config commit -m "Set db1183 with weight 0 T376867"
- Depool NEW from any specific group (API, vslow, dump) if present.
sudo dbctl instance db1183 edit # If some changes were made: sudo dbctl config commit -m "Remove db1183 from API/vslow/dump T376867"
- Topology changes, move all replicas under NEW primary
sudo db-switchover --timeout=25 --replicating-master --read-only-master --only-slave-move db1230 db1183
- Disable puppet on both nodes
sudo cumin 'db1230* or db1183*' 'disable-puppet "primary switchover T376867"'
- Merge gerrit puppet change to promote NEW primary: https://gerrit.wikimedia.org/r/1079083
Failover:
- Log the failover:
!log Starting s5 eqiad failover from db1230 to db1183 - T376867
- Switch primaries:
sudo db-switchover --replicating-master --read-only-master --skip-slave-move db1230 db1183 echo "===== db1230 (OLD)"; sudo db-mysql db1230 -e 'show slave status\G' echo "===== db1183 (NEW)"; sudo db-mysql db1183 -e 'show slave status\G'
- Promote NEW primary in dbctl
sudo dbctl --scope eqiad section s5 set-master db1183 sudo dbctl config commit -m "Promote db1183 to s5 primary T376867"
- Restart puppet on both hosts:
sudo cumin 'db1230* or db1183*' 'run-puppet-agent -e "primary switchover T376867"'
Clean up tasks:
- Clean up heartbeat table(s).
sudo db-mysql db1183 heartbeat -e "delete from heartbeat where file like 'db1230%';"
- 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 db1183 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 db1230
- Update candidate primary dbctl and orchestrator notes
sudo dbctl instance db1230 set-candidate-master --section s5 true sudo dbctl instance db1183 set-candidate-master --section s5 false sudo cumin 'dborch*' 'orchestrator-client -c untag -i db1183 --tag name=candidate' sudo cumin 'dborch*' 'orchestrator-client -c tag -i db1230 --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 db1230 for maintenance.
sudo dbctl instance db1230 depool sudo dbctl config commit -m "Depool db1230 T376867"
- Change db1230 weight to mimic the previous weight db1183:
sudo dbctl instance db1230 edit
- Apply outstanding schema changes to db1230 (if any)
- Update/resolve this ticket.