DNS - Connect exposed paths

[EtienneBruines]

Feature Description

Some way of accessing the port information for the exposed paths in Consul Connect services. This might require being able to "name" specific exposed paths, or to access the name of the listener_port that Nomad uses to configure the port used for the exposed path.

Use Case(s)

Discovering an exposed path of a Consul Connect service.

We want to connect to a Consul Connect service with a specific tag, but due to hashicorp/nomad#9914 and #11867 this seems impossible. We then attempted to expose the specific path we needed, accepting the loss of not using Consul Connect. But neither Consul DNS nor Consul Template ( hashicorp/consul-template#1730 ) offer any discoverability for this. Since this will be a dynamic port, discovering this port is kinda useful. Having to use the API is cumbersome, and in our use-case (configuring our haproxy as a Nomad job) impossible. We also tried creating tag-specific services (e.g. a new service per tag), but due to hashicorp/nomad#9741 we cannot do so dynamically using allocation information, e.g. ${NOMAD_DC}.

(The only other options we have at the moment, would be to deploy multiple Consul Datacenters, to forego of tags - or to deploy a specific Nomad job per tag, to forego of tagss and service-name string-interpolation.)