**When:** During a pre-defined DBA maintenance windows
**Affected wikis:**: https://noc.wikimedia.org/conf/highlight.php?file=dblists/s8.dblist
**Checklist:**
NEW primary: db2161
OLD primary: db2165
[x] Check configuration differences between new and old primary:
```
sudo pt-config-diff --defaults-file /root/.my.cnf h=db2165.codfw.wmnet h=db2161.codfw.wmnet
```
**Failover prep:**
[x] Silence alerts on all hosts:
```
sudo cookbook sre.hosts.downtime --hours 1 -r "Primary switchover s8 T368355" 'A:db-section-s8'
```
[x] Set NEW primary with weight 0
```
sudo dbctl instance db2161 set-weight 0
sudo dbctl config commit -m "Set db2161 with weight 0 T368355"
```
[x] Depool NEW from any specific group (API, vslow, dump) if present.
```
sudo dbctl instance db2161 edit
# If some changes were made:
sudo dbctl config commit -m "Remove db2161 from API/vslow/dump T368355"
```
[x] Topology changes, move all replicas under NEW primary
```
sudo db-switchover --timeout=25 --replicating-master --read-only-master --only-slave-move db2165 db2161
```
[x] Disable puppet on both nodes
```
sudo cumin 'db2165* or db2161*' 'disable-puppet "primary switchover T368355"'
```
[x] Merge gerrit puppet change to promote NEW primary: https://gerrit.wikimedia.org/r/c/operations/puppet/+/1049310/
**Failover:**
[] Log the failover:
```
!log Starting s8 codfw failover from db2165 to db2161 - T368355
```
[] Switch primaries:
```
sudo db-switchover --replicating-master --read-only-master --skip-slave-move db2165 db2161
echo "===== db2165 (OLD)"; sudo db-mysql db2165 -e 'show slave status\G'
echo "===== db2161 (NEW)"; sudo db-mysql db2161 -e 'show slave status\G'
```
[] Promote NEW primary in dbctl
```
sudo dbctl --scope codfw section s8 set-master db2161
sudo dbctl config commit -m "Promote db2161 to s8 primary T368355"
```
[] Restart puppet on both hosts:
```
sudo cumin 'db2165* or db2161*' 'run-puppet-agent -e "primary switchover T368355"'
```
**Clean up tasks:**
[] Clean up heartbeat table(s).
```
sudo db-mysql db2161 heartbeat -e "delete from heartbeat where file like 'db2165%';"
```
[] change events for query killer:
```
events_coredb_master.sql on the new primary db2161
events_coredb_slave.sql on the new slave db2165
```
[] Update candidate primary dbctl and orchestrator notes
```
sudo dbctl instance db2165 set-candidate-master --section s8 true
sudo dbctl instance db2161 set-candidate-master --section s8 false
(dborch1001): sudo orchestrator-client -c untag -i db2161 --tag name=candidate
(dborch1001): sudo orchestrator-client -c tag -i db2165 --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 = 's8';"
```
[] (If needed): Depool db2165 for maintenance.
```
sudo dbctl instance db2165 depool
sudo dbctl config commit -m "Depool db2165 T368355"
```
[] Change db2165 weight to mimic the previous weight db2161:
```
sudo dbctl instance db2165 edit
```
[] Apply outstanding schema changes to db2165 (if any)
[] Update/resolve this ticket.