**When:** During a pre-defined DBA maintenance windows
**Affected wikis:**: https://noc.wikimedia.org/conf/highlight.php?file=dblists/s1.dblist
**Checklist:**
NEW primary: db2203
OLD primary: db2212
[x] Check configuration differences between new and old primary:
```
sudo pt-config-diff --defaults-file /root/.my.cnf h=db2212.codfw.wmnet h=db2203.codfw.wmnet
```
**Failover prep:**
[x] Silence alerts on all hosts:
```
sudo cookbook sre.hosts.downtime --hours 1 -r "Primary switchover s1 T389373" 'A:db-section-s1'
```
[x] Set NEW primary with weight 0
```
sudo dbctl instance db2203 set-weight 0
sudo dbctl config commit -m "Set db2203 with weight 0 T389373"
```
[x] Depool NEW from any specific group (API, vslow, dump) if present.
```
sudo dbctl instance db2203 edit
# If some changes were made:
sudo dbctl config commit -m "Remove db2203 from API/vslow/dump T389373"
```
[x] Topology changes, move all replicas under NEW primary
```
sudo db-switchover --timeout=25 --replicating-master --read-only-master --only-slave-move db2212 db2203
```
db2212 crashed during the process - detected at 11:37 CEST
[x] Disable puppet on both nodes
```
sudo cumin 'db2212* or db2203*' 'disable-puppet "primary switchover T389373"'
```
[x] Merge gerrit puppet change to promote NEW primary: FIXME
**Failover:**
[x] Log the failover:
```
!log Starting s1 codfw failover from db2212 to db2203 - T389373
```
[x] Switch primaries:
```
sudo db-switchover --replicating-master --read-only-master --skip-slave-move db2212 db2203
echo "===== db2212 (OLD)"; sudo db-mysql db2212 -e 'show slave status\G'
echo "===== db2203 (NEW)"; sudo db-mysql db2203 -e 'show slave status\G'
```
[] Promote NEW primary in dbctl
```
sudo dbctl --scope codfw section s1 set-master db2203
sudo dbctl config commit -m "Promote db2203 to s1 primary T389373"
```
[] Clean up heartbeat table(s).
```
sudo db-mysql db2203 heartbeat -e "delete from heartbeat where file like 'db2212%';"
```
[] Restart puppet on both hosts:
```
sudo cumin 'db2212* or db2203*' 'run-puppet-agent -e "primary switchover T389373"'
```
**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 db2203
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 db2212
```
[] Update candidate primary dbctl and orchestrator notes
```
sudo dbctl instance db2212 set-candidate-master --section s1 true
sudo dbctl instance db2203 set-candidate-master --section s1 false
sudo cumin 'dborch*' 'orchestrator-client -c untag -i db2203 --tag name=candidate'
sudo cumin 'dborch*' 'orchestrator-client -c tag -i db2212 --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 = 's1';"
```
[] (If needed): Depool db2212 for maintenance.
```
sudo dbctl instance db2212 depool
sudo dbctl config commit -m "Depool db2212 T389373"
```
[] Change db2212 weight to mimic the previous weight db2203:
```
sudo dbctl instance db2212 edit
```
[] Apply outstanding schema changes to db2212 (if any)
[] Update/resolve this ticket.