As part of upgrading s6 to debian buster/mariadb 10.4, we need to switch the master to be db1173 (which is already running buster/10.4).
When: 27th April at 05:00 AM UTC.
Checklist:
[x] Double check db1173 has `report_host` enabled T271106
[] Create a task to communicate the chosen date and send an announcement to the community: TODO
NEW master: db1173
OLD master: db1131
[] Check configuration differences between new and old master:
`sudo pt-config-diff h=db1131.eqiad.wmnet,F=/root/.my.cnf h=db1173.eqiad.wmnet,F=/root/.my.cnf`
[] Silence alerts on all hosts:
`sudo cookbook sre.hosts.downtime --hours 1 -r "Master switchover s6 T282124" 'A:db-section-s6 and A:eqiad'`
[] Set NEW master with weight 0
`sudo dbctl instance db1173 set-weight 0`
`sudo dbctl config commit -m "Set db1173 with weight 0 T282124"
[] Topology changes, move all replicas under NEW master
`sudo db-switchover --timeout=15 --only-slave-move db1131.eqiad.wmnet db1173.eqiad.wmnet`
[] Disable puppet on both nodes
`sudo cumin 'db1131* or db1173*' 'disable-puppet "master switchover T282124"'
[] Merge gerrit puppet change to promote NEW master: TODO
**Failover:**