**When:** During a pre-defined DBA maintenance windows
**Affected wikis:**: https://noc.wikimedia.org/conf/highlight.php?file=dblists/s7.dblist
**Checklist:**
NEW primary: db1181
OLD primary: db1236
[] Check configuration differences between new and old primary:
```
sudo pt-config-diff --defaults-file /root/.my.cnf h=db1236.eqiad.wmnet h=db1181.eqiad.wmnet
```
**Failover prep:**
[] Silence alerts on all hosts:
```
sudo cookbook sre.hosts.downtime --hours 1 -r "Primary switchover s7 T416356" 'A:db-section-s7'
```
[] Set NEW primary with weight 0
```
sudo dbctl instance db1181 set-weight 0
sudo dbctl config commit -m "Set db1181 with weight 0 T416356"
```
[] 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 db1236 db1181
```
[] Disable puppet on both nodes
```
sudo cumin 'db1236* or db1181*' 'disable-puppet "primary switchover T416356"'
```
[] Merge gerrit puppet change to promote NEW primary: FIXME
**Failover:**
[] Log the failover:
```
!log Starting s7 eqiad failover from db1236 to db1181 - T416356
```
[] Switch primaries:
```
sudo db-switchover --replicating-master --read-only-master --skip-slave-move db1236 db1181
echo "===== db1236 (OLD)"; sudo db-mysql db1236 -e 'show slave status\G'
echo "===== db1181 (NEW)"; sudo db-mysql db1181 -e 'show slave status\G'
```
[] Promote NEW primary in dbctl
```
sudo dbctl --scope eqiad section s7 set-master db1181
sudo dbctl config commit -m "Promote db1181 to s7 primary T416356"
```
[] Clean up heartbeat table(s).
```
sudo db-mysql db1181 heartbeat -e "delete from heartbeat where file like 'db1236%';"
```
[] Restart puppet on both hosts:
```
sudo cumin 'db1236* or db1181*' 'run-puppet-agent -e "primary switchover T416356"'
```
**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 db1181
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 db1236
```
[] Update candidate primary dbctl and orchestrator notes
```
sudo dbctl instance db1236 set-candidate-master --section s7 true
sudo dbctl instance db1181 set-candidate-master --section s7 false
sudo cumin 'dborch*' 'orchestrator-client -c untag -i db1181 --tag name=candidate'
sudo cumin 'dborch*' 'orchestrator-client -c tag -i db1236 --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 = 's7';"
```
[] Depool db1236 for maintenance.
```
sudo dbctl instance db1236 depool
sudo dbctl config commit -m "Depool db1236 T416356"
```
[] Change db1236 weight to mimic the previous weight db1181:
```
sudo dbctl instance db1236 edit
```
[] Apply outstanding schema changes to db1236 (if any)
[] Slowly repool the db1236 if ready
```
sudo cookbook sre.mysql.pool -t T416356 -r "Repooling after switchover" db1236
```
[] Update/resolve this ticket.