Comment 4 for bug 1910974

I think the best solution here is to update the haproxy[1] and content-cache[2] to pass through the listen address for haproxy statistics, they both already pass through the username, password, and port. Then have the telegraf charm check the presence of this and use it if it's something other than 0.0.0.0. If it doesn't exist, try work it out with the existing code (rel["private-address"] and hookenv.unit_private_ip()).

For the HAProxy charm, it defaults to statistics on 0.0.0.0 so why it doesn't appear broken with the latest Juju version - localhost or private-address, HAProxy statistics will answer on both interfaces. For the Content-cache charm, it configures statistics to listen on 127.0.0.1.

[1]https://bazaar.launchpad.net/~haproxy-team/charm-haproxy/trunk/view/head:/hooks/hooks.py#L1437
[2]https://git.launchpad.net/~hloeung/content-cache-charm/tree/reactive/content_cache.py#n483