Due to some on-site maintenance on codfw we need to switch x2 master before Aug 2nd
This is the first time we'll do a master switchover on an active-active service, so it will be interesting to see how long it takes...
**When:** Thursday 28th 06:00 AM UTC
** Prerequisites **: https://wikitech.wikimedia.org/wiki/MariaDB/Primary_switchover
[x] Team calendar invite
**Affected wikis:**: x2
**Checklist:**
NEW primary: db2144
OLD primary: db2142
[x] Check configuration differences between new and old primary:
```
sudo pt-config-diff --defaults-file /root/.my.cnf h=db2142.codfw.wmnet h=db2144.codfw.wmnet
```
**Failover prep:**
[x] Silence alerts on all hosts:
```
sudo cookbook sre.hosts.downtime --hours 1 -r "Primary switchover x2 T313811" 'A:db-section-x2'
```
[x] Set NEW primary with weight 0 (and depool it from API or vslow/dump groups if it is present).
```
sudo dbctl instance db2144 set-weight 0
sudo dbctl config commit -m "Set db2144 with weight 0 T313811"
```
[x] Topology changes, move all replicas under NEW primary
```
This didn't work and I had to use orchestrator: sudo db-switchover --replicating-master --timeout=25 --only-slave-move db2142 db2144
```
[x] Disable puppet on both nodes
```
sudo cumin 'db2142* or db2144*' 'disable-puppet "primary switchover T313811"'
```
[x] Merge gerrit puppet change to promote NEW primary: https://gerrit.wikimedia.org/r/c/operations/puppet/+/817736/
**Failover:**
[] Log the failover:
```
!log Starting x2 codfw failover from db2142 to db2144 - T313811
```
[] Switch primaries:
```
sudo db-switchover --replicating-master --skip-slave-move db2142 db2144
echo "===== db2142 (OLD)"; sudo db-mysql db2142 -e 'show slave status\G'
echo "===== db2144 (NEW)"; sudo db-mysql db2144 -e 'show slave status\G'
```
[] Promote NEW primary in dbctl, and remove read-only
```
sudo dbctl --scope codfw section x2 set-master db2144
sudo dbctl config commit -m "Promote db2144 to x2 primary T313811"
```
[] Restart puppet on both hosts:
```
sudo cumin 'db2142* or db2144*' 'run-puppet-agent -e "primary switchover T313811"'
```
**Clean up tasks:**
[] Clean up heartbeat table(s).
```
sudo db-mysql db2144 heartbeat -e "delete from heartbeat where file like 'db2142%';"
```
[] change events for query killer:
```
events_coredb_master.sql on the new primary db2144
events_coredb_slave.sql on the new slave db2142
```
[] Update candidate primary dbctl and orchestrator notes
```
sudo dbctl instance db2142 set-candidate-master --section x2 true
sudo dbctl instance db2144 set-candidate-master --section x2 false
(dborch1001): sudo orchestrator-client -c untag -i db2144 --tag name=candidate
(dborch1001): sudo orchestrator-client -c tag -i db2142 --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 = 'x2';"
```
[] (If needed): Depool db2142 for maintenance.
```
sudo dbctl instance db2142 depool
sudo dbctl config commit -m "Depool db2142 T313811"
```
[] Change db2142 weight to mimic the previous weight db2144:
```
sudo dbctl instance db2142 edit
```
[] Apply outstanding schema changes to db2142 (if any)
[] Update/resolve this ticket.