**Checklist:**
NEW primary: db2113
OLD primary: db2123
[x] Check configuration differences between new and old primary:
```
sudo pt-config-diff --defaults-file /root/.my.cnf h=db2123.codfw.wmnet h=db2113.codfw.wmnet
```
**Failover prep:**
[] Silence alerts on all hosts:
```
sudo cookbook sre.hosts.downtime --hours 1 -r "Primary switchover s2 T317735" 'A:db-section-s2'
```
[] Set NEW primary with weight 0 (and depool it from API or vslow/dump groups if it is present).
```
sudo dbctl instance db2113 set-weight 0
sudo dbctl config commit -m "Set db2113 with weight 0 T317735"
```
[] Topology changes, move all replicas under NEW primary
```
sudo db-switchover --timeout=25 --only-slave-move db2123 db2113
```
[] Disable puppet on both nodes
```
sudo cumin 'db2123* or db2113*' 'disable-puppet "primary switchover T317735"'
```
[] Merge gerrit puppet change to promote NEW primary: FIXME
**Failover:**
[] Log the failover:
```
!log Starting s2 codfw failover from db2123 to db2113 - T317735
```
[] Switch primaries:
```
sudo db-switchover --skip-slave-move db2123 db2113
echo "===== db2123 (OLD)"; sudo db-mysql db2123 -e 'show slave status\G'
echo "===== db2113 (NEW)"; sudo db-mysql db2113 -e 'show slave status\G'
```
[] Promote NEW primary in dbctl, and remove read-only
```
sudo dbctl --scope codfw section s2 set-master db2113
sudo dbctl config commit -m "Promote db2113 to s2 codfw primary T317735"
```
[] Restart puppet on both hosts:
```
sudo cumin 'db2123* or db2113*' 'run-puppet-agent -e "primary switchover T317735"'
```
**Clean up tasks:**
[] Clean up heartbeat table(s).
```
sudo db-mysql db2113 heartbeat -e "delete from heartbeat where file like 'db2123%';"
```
[] change events for query killer:
```
events_coredb_master.sql on the new primary db2113
events_coredb_slave.sql on the new slave db2123
```
[] Update candidate primary dbctl and orchestrator notes
```
sudo dbctl instance db2123 set-candidate-master --section s2 true
sudo dbctl instance db2113 set-candidate-master --section s2 false
(dborch1001): sudo orchestrator-client -c untag -i db2113 --tag name=candidate
(dborch1001): sudo orchestrator-client -c tag -i db2123 --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 db1115 zarcillo -e "select * from masters where section = 's2';"
```
[] (If needed): Depool db2123 for maintenance.
```
sudo dbctl instance db2123 depool
sudo dbctl config commit -m "Depool db2123 T317735"
```
[] Change db2123 weight to mimic the previous weight db2113:
```
sudo dbctl instance db2123 edit
```
[] Update/resolve this ticket.