Add consul exposed sidecar ports

[jorgemarey]

Proposal

Add consul exposed ports using sidecars to the target labels.

Consul has the ability to expose paths for aplications making the service port only accesible internally but some application paths could be consumed externally (as /metrics for example). This can be seen in the consul documentation: https://www.consul.io/docs/connect/registration/service-registration#expose-paths-configuration-reference

This would allow us to deploy applications with the consul connect sidecar, but expose the metrics to be consumed by prometheus externally.

Regarding implementation details. On the consul discovery if the service is a proxy exposed paths could be iterated and returned as labels (for example __meta_consul_exposed_path_<path>_port: listener_port)

[roidelapluie]

Thanks for this request.

We would need both: listener_port and local_path_port.

[jorgemarey]

Hi @roidelapluie I will give a it a try and make a PR for this.

[roidelapluie]

Thanks!! awesome!! Do not focus on only the port, try to see which meta are interesting in the complete consul connect metadata.

[jorgemarey]

Yeah, will do that.

[jorgemarey]

Hi again @roidelapluie. Made a PR in #7800. Let me know if anything should be changed/added or removed. Some label names may be too long, but I didn't know how to make them descriptive and short.

[bwplotka]

Hello from the Bug Scrub!

There is no recent activity here, still to do, the last PR was abandoned. Still it looks like something to be done, and it's not too difficult. We decided to add an agenda to DevSummit around SD maintainers/cleanup of those to improve reviewing cycles here. Leaving that open for now, with help wanted.