**Checklist:**
NEW primary: db2114
OLD primary: db2129
[x] Check configuration differences between new and old primary:
```
sudo pt-config-diff --defaults-file /root/.my.cnf h=db2129.codfw.wmnet h=db2114.codfw.wmnet
```
**Failover prep:**
[] Silence alerts on all hosts:
```
sudo cookbook sre.hosts.downtime --hours 1 -r "Primary codfw s6 T317850" 'A:db-section-s6'
```
[] Set NEW primary with weight 0 (and depool it from API or vslow/dump groups if it is present).
```
sudo dbctl instance db2114 set-weight 0
sudo dbctl config commit -m "Set db2114 with weight 0 T317850"
```
[] Topology changes, move all replicas under NEW primary
```
sudo db-switchover --replicating-master --read-only-master --timeout=25 --only-slave-move db2129 db2114
```
[] Disable puppet on both nodes
```
sudo cumin 'db2129* or db2114*' 'disable-puppet "primary switchover T317850"'
```
[] Merge gerrit puppet change to promote NEW primary: FIXME
**Failover:**
[] Log the failover:
```
!log Starting s6 codfw failover from db2129 to db2114 - T317850
```
[] Switch primaries:
```
sudo db-switchover --replicating-master --read-only-master --skip-slave-move db2129 db2114
echo "===== db2129 (OLD)"; sudo db-mysql db2129 -e 'show slave status\G'
echo "===== db2114 (NEW)"; sudo db-mysql db2114 -e 'show slave status\G'
```
[] Promote NEW primary in dbctl, and remove read-only
```
sudo dbctl --scope codfw section s6 set-master db2114
sudo dbctl config commit -m "Promote db2114 to s6 codfw master T317850"
```
[] Restart puppet on both hosts:
```
sudo cumin 'db2129* or db2114*' 'run-puppet-agent -e "primary switchover T317850"'
```
**Clean up tasks:**
[] Clean up heartbeat table(s).
```
sudo db-mysql db2114 heartbeat -e "delete from heartbeat where file like 'db2129%';"
```
[] change events for query killer:
```
events_coredb_master.sql on the new primary db2114
events_coredb_slave.sql on the new slave db2129
```
[] Update candidate primary dbctl and orchestrator notes
```
sudo dbctl instance db2129 set-candidate-master --section s6 true
sudo dbctl instance db2114 set-candidate-master --section s6 false
(dborch1001): sudo orchestrator-client -c untag -i db2114 --tag name=candidate
(dborch1001): sudo orchestrator-client -c tag -i db2129 --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 = 's6';"
```
[] (If needed): Depool db2129 for maintenance.
```
sudo dbctl instance db2129 depool
sudo dbctl config commit -m "Depool db2129 T317850"
```
[] Change db2129 weight to mimic the previous weight db2114:
```
sudo dbctl instance db2129 edit
```
[] Update/resolve this ticket.