**When:** Anytime, DC switch only.
** Prerequisites **: https://wikitech.wikimedia.org/wiki/MariaDB/Primary_switchover
**Checklist:**
NEW primary: db2115
OLD primary: db2096
[x] Check that db2115 is running STATEMENT and the latest kernel
** The STATEMENT part is covered by https://gerrit.wikimedia.org/r/c/operations/puppet/+/827491
[x] Check configuration differences between new and old primary:
```
sudo pt-config-diff --defaults-file /root/.my.cnf h=db2096.codfw.wmnet h=db2115.codfw.wmnet
```
**Failover prep:**
[] Silence alerts on all hosts:
```
sudo cookbook sre.hosts.downtime --hours 1 -r "DC switchover x1 T316522" 'A:db-section-x1'
```
[] Set NEW primary with weight 0 (and depool it from API or vslow/dump groups if it is present).
```
sudo dbctl instance db2115 set-weight 0
sudo dbctl config commit -m "Set db2115 with weight 0 T316522"
```
[] Topology changes, move all replicas under NEW primary
```
sudo db-switchover --timeout=25 --only-slave-move db2096 db2115
```
[] Disable puppet on both nodes
```
sudo cumin 'db2096* or db2115*' 'disable-puppet "primary switchover T316522"'
```
[] Merge gerrit puppet change to promote NEW primary: https://gerrit.wikimedia.org/r/c/operations/puppet/+/827864
**Failover:**
[] Log the failover:
```
!log Starting x1 codfw failover from db2096 to db2115 - T316522
```
[] Switch primaries:
```
sudo db-switchover --replicating-master --read-only-master --skip-slave-move db2096 db2115
echo "===== db2096 (OLD)"; sudo db-mysql db2096 -e 'show slave status\G'
echo "===== db2115 (NEW)"; sudo db-mysql db2115 -e 'show slave status\G'
```
[] Promote NEW primary in dbctl, and remove read-only
```
sudo dbctl --scope codfw section x1 set-master db2115
sudo dbctl config commit -m "Promote db2115 to x1 codfw primary T316522"
```
[] Restart puppet on both hosts:
```
sudo cumin 'db2096* or db2115*' 'run-puppet-agent -e "primary switchover T316522"'
```
**Clean up tasks:**
[] Clean up heartbeat table(s).
```
sudo db-mysql db2115 heartbeat -e "delete from heartbeat where file like 'db2096%';"
```
[] change events for query killer:
```
events_coredb_master.sql on the new primary db2115
events_coredb_slave.sql on the new slave db2096
```
[] Update candidate primary dbctl and orchestrator notes
```
sudo dbctl instance db2096 set-candidate-master --section x1 true
sudo dbctl instance db2115 set-candidate-master --section x1 false
(dborch1001): sudo orchestrator-client -c untag -i db2115 --tag name=candidate
(dborch1001): sudo orchestrator-client -c tag -i db2096 --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 = 'x1';"
```
[] (If needed): Depool db2096 for maintenance.
```
sudo dbctl instance db2096 depool
sudo dbctl config commit -m "Depool db2096 T316522"
```
[] Change db2096 weight to mimic the previous weight db2115:
```
sudo dbctl instance db2096 edit
```
[] Apply outstanding schema changes to db2096 (if any)
[] Update/resolve this ticket.