The beta cluster MySQL servers turned out to be down for a few hours (T96905) and there is no monitoring for it.

We would need on both instances a check to ensure the mysql process is running.

The command line looks like:

/usr/sbin/mysqld --basedir=/usr --datadir=/mnt/sqldata \
  --plugin-dir=/usr/lib/mysql/plugin --user=mysql \
  --log-error=/mnt/sqldata/deployment-db1.err \
  --pid-file=/mnt/sqldata/deployment-db1.pid \
  --socket=/tmp/mysql.sock --port=3306

I guess we can just monitor whether /usr/bin/mysqld is present.