We are already caching any DB_HOST and REDIS_HOST (and their
accompanying replicas), we should also cache the resolved addresses for
the MessageBus specific Redis. This is a noop if no MB redis is defined
in config. A side effect is that the MB will also support SRV lookup and
priorities, following the same convention as the other cached services.
The port argument was added to redis_healthcheck so that the script
supports a setup where Redis is running on a non-default port.
Did some minor refactoring to improve readability when filtering out the
CRITICAL_HOST_ENV_VARS. The `select` block was a bit confusing, so the
sequence was made easier to follow.
We were coercing an environment variable to an int in a few places, so
the `env_as_int` method was introduced to do that coercion in one place and
for convenience purposes default to a value if provided.
See /t/68301/30.
5fdbbe3045