Databases on m3: phabricator
When: Today ASAP
Impact: Writes will be disabled for around 1 minute.

Failover process

OLD MASTER: db1159

NEW MASTER: db1101

• Check configuration differences between new and old master

$ pt-config-diff h=db1101.eqiad.wmnet,F=/root/.my.cnf h=db1159.eqiad.wmnet,F=/root/.my.cnf

• Silence alerts on all hosts: sudo cookbook sre.hosts.downtime --hours 1 -r "m3 master switchover T331384" 'A:db-section-m3'
• Topology changes: move everything under db1101

db-switchover --timeout=15 --only-slave-move db1159.eqiad.wmnet db1101.eqiad.wmnet

• Disable puppet db1159 and db1101 sudo cumin 'db1101* or db1159*' 'disable-puppet "primary switchover T331384"'
• Merge gerrit: https://gerrit.wikimedia.org/r/c/operations/puppet/+/895066
• Run puppet on dbproxy1016 and dbproxy1020 and check the config

run-puppet-agent && cat /etc/haproxy/conf.d/db-master.cfg

• Start the failover: !log Failover m3 from db1159 to db1101 - T331384
• Set phabricator in RO:

ssh phab1004
    sudo /srv/phab/phabricator/bin/config set cluster.read-only true
    # restart database server
    sudo /srv/phab/phabricator/bin/config set cluster.read-only false

• DB switchover

root@cumin1001:~/wmfmariadbpy/wmfmariadbpy# db-switchover --skip-slave-move db1159 db1101

• Reload haproxies

dbproxy1016:   systemctl reload haproxy && echo "show stat" | socat /run/haproxy/haproxy.sock stdio
dbproxy1020:   systemctl reload haproxy && echo "show stat" | socat /run/haproxy/haproxy.sock stdio

• kill connections on the old master (db1159)

pt-kill --print --kill --victims all --match-all F=/dev/null,S=/run/mysqld/mysqld.sock

• Restart puppet on old and new masters (for heartbeat):db1159 and db1101 sudo cumin 'db1159* or db1101*' 'run-puppet-agent -e "primary switchover T331384"'
• Check services affected: phabricator
• Clean orchestrator heartbeat to remove the old masters' one, otherwise Orchestrator will show lag: delete from heartbeat where server_id=171966512;
• Close this ticket and create a ticket to promote db1159 back to m3 master once T329073 is finished: T331387