When: Thursday 31th - 06:00 AM UTC
**Affected wikis:** https://noc.wikimedia.org/conf/highlight.php?file=dblists/s5.dblist
NEW primary: db1100
OLD primary: db1130
[x] Check configuration differences between new and old primary:
```
sudo pt-config-diff --defaults-file /root/.my.cnf h=db1130.eqiad.wmnet h=db1100.eqiad.wmnet
```
**Failover prep:**
[x] Silence alerts on all hosts:
```
sudo cookbook sre.hosts.downtime --hours 1 -r "Primary switchover s5 T303798" 'A:db-section-s5'
```
[x] Set NEW primary with weight 0
```
sudo dbctl instance db1100 set-weight 0
sudo dbctl config commit -m "Set db1100 with weight 0 T303798"
```
[x] Topology changes, move all replicas under NEW primary
```
sudo db-switchover --timeout=15 --only-slave-move db1130 db1100
```
[x] Disable puppet on both nodes
```
sudo cumin 'db1130* or db1100*' 'disable-puppet "primary switchover T303798"'
```
[x] Merge gerrit puppet change to promote NEW primary: https://gerrit.wikimedia.org/r/c/operations/puppet/+/775195
**Failover:**
[x] Log the failover:
```
!log Starting s5 eqiad failover from db1130 to db1100 - T303798
```
[x] Set section read-only:
```
sudo dbctl --scope eqiad section s5 ro "Maintenance until 05:15 UTC - T303798"
sudo dbctl config commit -m "Set s5 eqiad as read-only for maintenance - T303798"
```
[x] Check s5 is indeed read-only
[x] Switch primaries:
```
sudo db-switchover --skip-slave-move db1130 db1100
echo "===== db1130 (OLD)"; sudo db-mysql db1130 -e 'show slave status\G'
echo "===== db1100 (NEW)"; sudo db-mysql db1100 -e 'show slave status\G'
```
[x] Promote NEW primary in dbctl, and remove read-only
```
sudo dbctl --scope eqiad section s5 set-master db1100
sudo dbctl --scope eqiad section s5 rw
sudo dbctl config commit -m "Promote db1100 to s5 primary and set section read-write T303798"
```
[x] Restart puppet on both hosts:
```
sudo cumin 'db1130* or db1100*' 'run-puppet-agent -e "primary switchover T303798"'
```
**Clean up tasks:**
[x] Clean up heartbeat table(s). `delete from heartbeat.heartbeat where server_id=171970593`
[] change events for query killer:
```
events_coredb_master.sql on the new primary db1100
events_coredb_slave.sql on the new slave db1130
```
[x] Update DNS: https://gerrit.wikimedia.org/r/c/operations/dns/+/775196
[x] Update candidate primary dbctl notes
```
sudo dbctl instance db1130 set-candidate-master --section s5 true
sudo dbctl instance db1100 set-candidate-master --section s5 false
```
[] Check zarcillo was updated
** db-switchover should do this. If it fails, do it manually: https://phabricator.wikimedia.org/P13956
[] (If needed): Depool db1130 for maintenance.
```
sudo dbctl instance db1130 depool
sudo dbctl config commit -m "Depool db1130 T303798"
(dborch1001): sudo orchestrator-client -c untag -i db1100 --tag name=candidate
(dborch1001): sudo orchestrator-client -c tag -i db1130 --tag name=candidate
```
[] Apply outstanding schema changes to db1130 (if any)
[] Update/resolve this ticket.