**When:** Anytime - no in use
**Prerequisites**: https://wikitech.wikimedia.org/wiki/MariaDB/Primary_switchover
**Checklist:**
NEW primary: es1037
OLD primary: es1038
[] Check configuration differences between new and old primary:
```
sudo pt-config-diff --defaults-file /root/.my.cnf h=es1038.eqiad.wmnet h=es1037.eqiad.wmnet
```
**Failover prep:**
[] Silence alerts on all hosts:
```
sudo cookbook sre.hosts.downtime --hours 1 -r "Primary switchover es6 T387273" 'A:db-section-es6'
```
[] Set NEW primary with weight 0 (and depool it from API or vslow/dump groups if it is present).
```
sudo dbctl instance es1037 set-weight 0
sudo dbctl config commit -m "Set es1037 with weight 0 T387273"
```
[] Topology changes, move all replicas under NEW primary
```
sudo db-switchover --read-only-master --replicating-master --timeout=25 --only-slave-move es1038 es1037
```
[] Disable puppet on both nodes
```
sudo cumin 'es1038* or es1037*' 'disable-puppet "primary switchover T387273"'
```
[] Merge gerrit puppet change to promote NEW primary: FIXME
**Failover:**
[] Log the failover:
```
!log Starting es6 eqiad failover from es1038 to es1037 - T387273
```
[] Switch primaries:
```
sudo db-switchover --read-only-master --replicating-master --skip-slave-move es1038 es1037
echo "===== es1038 (OLD)"; sudo db-mysql es1038 -e 'show slave status\G'
echo "===== es1037 (NEW)"; sudo db-mysql es1037 -e 'show slave status\G'
```
[] Promote NEW primary in dbctl, and remove read-only
```
sudo dbctl --scope eqiad section es6 set-master es1037
sudo dbctl --scope eqiad section es6 rw
sudo dbctl config commit -m "Promote es1037 to es6 primary and set section read-write T387273"
```
[] Clean up heartbeat table(s).
```
sudo db-mysql es1037 heartbeat -e "delete from heartbeat where file like 'es1038%';"
```
[] Restart puppet on both hosts:
```
sudo cumin 'es1038* or es1037*' 'run-puppet-agent -e "primary switchover T387273"'
```
**Clean up tasks:**
[] change events for query killer:
```
curl -sS 'https://gerrit.wikimedia.org/r/plugins/gitiles/operations/software/+/refs/heads/master/dbtools/events_coredb_master.sql?format=TEXT' | base64 -d | sudo db-mysql es1037
curl -sS 'https://gerrit.wikimedia.org/r/plugins/gitiles/operations/software/+/refs/heads/master/dbtools/events_coredb_slave.sql?format=TEXT' | base64 -d | sudo db-mysql es1038
```
[] Update candidate primary dbctl and orchestrator notes
```
sudo dbctl instance es1038 set-candidate-master --section es6 true
sudo dbctl instance es1037 set-candidate-master --section es6 false
sudo cumin 'dborch*' 'orchestrator-client -c untag -i es1037 --tag name=candidate'
sudo cumin 'dborch*' 'orchestrator-client -c tag -i es1038 --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 = 'es6';"
```
[] (If needed): Depool es1038 for maintenance.
```
sudo dbctl instance es1038 depool
sudo dbctl config commit -m "Depool es1038 T387273"
```
[] Change es1038 weight to mimic the previous weight es1037:
```
sudo dbctl instance es1038 edit
```
[] Update/resolve this ticket.