**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: db2229
[] Check configuration differences between new and old primary:
```
sudo pt-config-diff --defaults-file /root/.my.cnf h=db2229.codfw.wmnet h=db2214.codfw.wmnet
```
**Failover prep:**
[] Silence alerts on all hosts:
```
sudo cookbook sre.hosts.downtime --hours 1 -r "Primary switchover s6 T430964" '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 T430964"
```
[] Topology changes, move all replicas under NEW primary, open orchestartor to monitor the process and check it at the end.
```
sudo db-switchover --timeout=25 --replicating-master --read-only-master --only-slave-move db2229 db2214
```
[] Disable puppet on both nodes
```
sudo cumin 'db2229* or db2214*' 'disable-puppet "primary switchover T430964"'
```
[] Merge gerrit puppet change to promote NEW primary: FIXME
```
ssh puppetserver1001.eqiad.wmnet
sudo puppet-merge
```
**Failover:**
[] Log the failover:
```
!log Starting s6 codfw failover from db2229 to db2214 - T430964
```
[] Switch primaries:
```
sudo db-switchover --replicating-master --read-only-master --skip-slave-move db2229 db2214
echo "===== db2229 (OLD)"; sudo db-mysql db2229 -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 T430964"
```
[] Clean up heartbeat table(s).
```
sudo db-mysql db2214 heartbeat -e "delete from heartbeat where file like 'db2229%';"
```
[] Restart puppet on both hosts:
```
sudo cumin 'db2229* or db2214*' 'run-puppet-agent -e "primary switchover T430964"'
```
**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 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 db2229
```
[] Update candidate primary dbctl and orchestrator notes
```
sudo dbctl instance db2229 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 db2229 --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';"
```
[] Depool db2229 for maintenance.
```
sudo dbctl instance db2229 depool
sudo dbctl config commit -m "Depool db2229 T430964"
```
[] Change db2229 weight to mimic the previous weight db2214:
```
sudo dbctl instance db2229 edit
```
[] Apply outstanding schema changes to db2229 (if any)
[] Slowly repool the db2229 if ready
```
sudo cookbook sre.mysql.pool -t T430964 -r "Repooling after switchover" db2229
```
[] Update/resolve this ticket.