Support tcp scheme for DOCKER_HOST

[fmanzali]

I am running the CLI in a GitLab CI pipeline, but if I try to update it to v1.29.8 or later, I get this error:

failed to generate docker-compose.yaml: failed to get docker host: unsupported scheme tcp in DOCKER_HOST, only unix supported

The issue stems from this update. When using Docker-in-Docker on GitLab, the scheme (on a shared runner) is tcp, not unix (see the docs). In fact, my CI works by setting this environment variable: DOCKER_HOST: tcp://docker:2375/.

Is it possible to allow the tcp scheme? Or is there a specific reason for why only the unix scheme is now allowed?

[dbarrosop]

Prior to that PR it was harcoded to unix:///var/run/docker.sock so you can try setting it to that value in your CI to restore pre-1.29.8 behavior:

https://github.com/nhost/cli/pull/959/files#diff-67d473eea1a53a8257f907983067eaabe35308b83d3a28d7f7705e7dfa396c40L244-R257

Supporting tcp is tricky because traefik needs to interact with docker to configure itself and I am unsure if it is even supported.

[fmanzali]

I tried rerunning the CI with v1.30.0 using DOCKER_HOST=unix:///var/run/docker.sock nhost up. Unfortunately this does not work at all on a GitLab shared runner, since the Docker API is provided only via tcp, and it is not possible to bind the /var/run/docker.sock (actually I'm not sure how it was working before).

However, it looks like traefik does support tcp, if I'm understanding correctly this page in the docs: Traefik Provider Configuration. If so, it should be possible to support it in compose.go.

[dbarrosop]

I really don't understand how it worked before but anyway, opened a PR that may address the issue. Unfortunately I cannot test it but hopefully it will work (at least it doesn't break the case we currently support)

[fmanzali]

I'm getting back with feedback after a long time. So basically for some reason using the tcp scheme does not really work on GitLab shared runners, even after the patch, and even if the docs suggest that it should work (yet I have still no idea why).

But I managed to find a workaround, which may be of relevance for whoever attempts to run the nhost-cli on GitLab CI/CD. The basic idea is to remap the tcp://docker:2375 host that GitLab forces us to use to the unix:///var/run/docker.sock scheme.

Assuming that nhost-cli and socat are already installed, these are the commands to add to a script: section in .gitlab-ci.yml:

script:
  - socat -d UNIX-LISTEN:/var/run/docker.sock,fork,reuseaddr,unlink-early,mode=777,max-children=4,backlog=100 TCP-CONNECT:docker:2375 &
  - nhost up

This has been stable for a few weeks now, so it should be viable.