[v2] prometheus and health checks listen on localhost instead of anyhost

[daquinoaldo]

Bug Description

When started with "--prometheus and --health-check, the HTTP server listens for requests on localhost, but it should listen on anyhost. Otherwise, it cannon be accessed using the Pod IP (from Prometheus, kubelet, and Istio).

How to reproduce

1. Run the Pod with --health-check
2. Create an ephemeral container with debug and run curl localhost:9090/readiness and curl <pod IP>:9090/readiness. The latter won't work.

Environment

• GKE 1.23 with COS containerd nodes
• Cloud SQL Proxy version: docker container built from the v2.0.0.preview.0 tag, targeting Linux amd64

EDIT: I can open a pull request if you want. I tested it, and it worked by replacing localhost with 0.0.0.0 in the HTTP server.

[enocom]

Thanks for the bug report. I think defaulting to localhost but letting people change the host with a flag is the way to go here. What do you think @daquinoaldo?

[enocom]

I’m thinking mostly about supporting this feature on GCE where any host could be a security problem.

[daquinoaldo]

Sorry for the late reply. Sure, a flag does the job!
I added a couple of comments in the PR. Thank you for taking care of it!