**When:** During a pre-defined DBA maintenance windows
**Affected wikis:**: https://noc.wikimedia.org/conf/highlight.php?file=dblists/s2.dblist
**Checklist:**
NEW primary: db2207
OLD primary: db2204
[] Check configuration differences between new and old primary:
```
sudo pt-config-diff --defaults-file /root/.my.cnf h=db2204.codfw.wmnet h=db2207.codfw.wmnet
```
**Failover prep:**
[] Silence alerts on all hosts:
```
sudo cookbook sre.hosts.downtime --hours 1 -r "Primary switchover s2 T434565" 'A:db-section-s2'
```
[] Set NEW primary with weight 0
```
sudo dbctl instance db2207 set-weight 0
sudo dbctl config commit -m "Set db2207 with weight 0 T434565"
```
[] 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 db2204 db2207
```
[] Disable puppet on both nodes
```
sudo cumin 'db2204* or db2207*' 'disable-puppet "primary switchover T434565"'
```
[] Merge gerrit puppet change to promote NEW primary: FIXME
```
ssh puppetserver1001.eqiad.wmnet
sudo puppet-merge
```
**Failover:**
[] Log the failover:
```
!log Starting s2 codfw failover from db2204 to db2207 - T434565
```
[] Switch primaries:
```
sudo db-switchover --replicating-master --read-only-master --skip-slave-move db2204 db2207
echo "===== db2204 (OLD)"; sudo db-mysql db2204 -e 'show slave status\G'
echo "===== db2207 (NEW)"; sudo db-mysql db2207 -e 'show slave status\G'
```
[] Promote NEW primary in dbctl
```
sudo dbctl --scope codfw section s2 set-master db2207
sudo dbctl config commit -m "Promote db2207 to s2 primary T434565"
```
[] Clean up heartbeat table(s).
```
sudo db-mysql db2207 heartbeat -e "delete from heartbeat where file like 'db2204%';"
```
[] Restart puppet on both hosts:
```
sudo cumin 'db2204* or db2207*' 'run-puppet-agent -e "primary switchover T434565"'
```
**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 db2207
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 db2204
```
[] Update candidate primary dbctl and orchestrator notes
```
sudo dbctl instance db2204 set-candidate-master --section s2 true
sudo dbctl instance db2207 set-candidate-master --section s2 false
sudo cumin 'dborch*' 'orchestrator-client -c untag -i db2207 --tag name=candidate'
sudo cumin 'dborch*' 'orchestrator-client -c tag -i db2204 --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 = 's2';"
```
[] Depool db2204 for maintenance.
```
sudo dbctl instance db2204 depool
sudo dbctl config commit -m "Depool db2204 T434565"
```
[] Change db2204 weight to mimic the previous weight db2207:
```
sudo dbctl instance db2204 edit
```
[] Apply outstanding schema changes to db2204 (if any)
[] Slowly repool the db2204 if ready
```
sudo cookbook sre.mysql.pool -t T434565 -r "Repooling after switchover" db2204
```
[] Update/resolve this ticket.