Docs: Extend TLS documentation to include Memcached and memcached_exporter.

[bradleypettit]

Is your documentation request related to a feature? If so, which one?

This request is related to running Mimir (and also Grafana Enterprise Metrics) with encryption in transit end to end. It's most likely an extension to this existing documentation - Securing Communications with TLS (Mimir) and Secure (GEM).

Describe the solution that you’d like or the expected outcome

The current documentation describes configuring TLS between Mimir components. It should be extended to document how to configure TLS communications between Mimir and Memcached, and also between memcached_exporter and Memcached.

[56quarters]

and also between memcached_exporter and Memcached.

This is unnecessary. Memcached and the exporter run as two containers in the same pod. When running Memcached with TLS we specifically configure Memcached to allow non-TLS connections locally.

[bradleypettit]

and also between memcached_exporter and Memcached.

This is unnecessary. Memcached and the exporter run as two containers in the same pod. When running Memcached with TLS we specifically configure Memcached to allow non-TLS connections locally.

That's a great reference - thanks for sharing Nick. I think we should document both, as I agree it's not really necessary, but we do have customers who have a blanket requirement that if it supports TLS, it must be configured to use it.

Ideally I'll contribute some improvements to the Helm chart to make these things more easily configurable, but documenting them as a starting point will be very helpful.