**When:** During a pre-defined DBA maintenance windows
**Affected wikis:**: https://noc.wikimedia.org/conf/highlight.php?file=dblists/s2.dblist
**Checklist:**
NEW primary: db2204
OLD primary: db2107
[x] Check configuration differences between new and old primary:
```
sudo pt-config-diff --defaults-file /root/.my.cnf h=db2107.codfw.wmnet h=db2204.codfw.wmnet
```
**Failover prep:**
[x] Silence alerts on all hosts:
```
sudo cookbook sre.hosts.downtime --hours 1 -r "Primary switchover s2 T361682" 'A:db-section-s2'
```
[x] Set NEW primary with weight 0 (and depool it from API or vslow/dump groups if it is present).
```
sudo dbctl instance db2204 set-weight 0
sudo dbctl config commit -m "Set db2204 with weight 0 T361682"
```
[x] Topology changes, move all replicas under NEW primary
```
sudo db-switchover --timeout=25 --replicating-master --read-only-master --only-slave-move db2107 db2204
```
[x] Disable puppet on both nodes
```
sudo cumin 'db2107* or db2204*' 'disable-puppet "primary switchover T361682"'
```
[x] Merge gerrit puppet change to promote NEW primary: FIXME
**Failover:**
[x] Log the failover:
```
!log Starting s2 codfw failover from db2107 to db2204 - T361682
```
[x] Switch primaries:
```
sudo db-switchover --replicating-master --read-only-master --skip-slave-move db2107 db2204
echo "===== db2107 (OLD)"; sudo db-mysql db2107 -e 'show slave status\G'
echo "===== db2204 (NEW)"; sudo db-mysql db2204 -e 'show slave status\G'
```
[x] Promote NEW primary in dbctl
```
sudo dbctl --scope codfw section s2 set-master db2204
sudo dbctl config commit -m "Promote db2204 to s2 primary T361682"
```
[x] Restart puppet on both hosts:
```
sudo cumin 'db2107* or db2204*' 'run-puppet-agent -e "primary switchover T361682"'
```
**Clean up tasks:**
[] Clean up heartbeat table(s).
```
sudo db-mysql db2204 heartbeat -e "delete from heartbeat where file like 'db2107%';"
```
[] change events for query killer:
```
events_coredb_master.sql on the new primary db2204
events_coredb_slave.sql on the new slave db2107
```
[] Update candidate primary dbctl and orchestrator notes
```
sudo dbctl instance db2107 set-candidate-master --section s2 true
sudo dbctl instance db2204 set-candidate-master --section s2 false
(dborch1001): sudo orchestrator-client -c untag -i db2204 --tag name=candidate
(dborch1001): sudo orchestrator-client -c tag -i db2107 --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';"
```
[] (If needed): Depool db2107 for maintenance.
```
sudo dbctl instance db2107 depool
sudo dbctl config commit -m "Depool db2107 T361682"
```
[] Change db2107 weight to mimic the previous weight db2204:
```
sudo dbctl instance db2107 edit
```
[] Apply outstanding schema changes to db2107 (if any)
[] Update/resolve this ticket.