Define a Docker health check

[GergelyKalmar]

Feature Description

I'd like to use Docker Compose's health checks to bring up the proxy before starting dependent services, but I can't seem to be able to ping the readiness endpoints from within the container image.

It would be awesome if there was a health check defined in the cloud-sql-proxy image itself (see https://docs.docker.com/engine/reference/builder/#healthcheck).

Sample code

No response

Alternatives Considered

I tried pinging the existing readiness endpoint:

services:
  ...
  cloud_sql_proxy:
    ...
    healthcheck:
      test: ['CMD', 'curl', '-f', 'http://localhost:9999/readiness']
      interval: 3s
      timeout: 3s
      retries: 5

However, it seems that curl is not available in the Docker image, and neither is any other utility that would allow one to hit the readiness endpoint.

Additional Details

No response

[jackwotherspoon]

Hi @GergelyKalmar thanks for raising an issue on the Cloud SQL Proxy 😄

I'll take a look into this and see about adding a built-in health check to the docker image.

[enocom]

I bet the new wait command would be a perfect fit for this: #2041. @GergelyKalmar Do you think the new wait command would help?

In terms of Kubernetes, I see the Docker healthcheck has been disabled for years now: kubernetes/kubernetes#50703. So I think that means we could safely add a health check to our images without affecting kubernetes.

[GergelyKalmar]

Hm, I'm not yet sure if the wait command helps. In this case we would want to wait until the image itself is ready to serve traffic (as opposed to waiting for proxysql running in a separate process).

[enocom]

Got it. I think it would be nice if we could avoid a dependency on curl or similar, such that people could use this with the distroless container. Maybe cloud-sql-proxy ready that exits 0 or otherwise?

[GergelyKalmar]

Sure, that should work fine!