Network Per Build feature does not be to work

I am trying to run angular E2E testing in a pipeline. I want my entire app (front-end / backend) handled by the pipeline, by defining them as services. I have tried everything I could think of, the services do not see each other at all.

My gitlab-ci script is somewhat like this:

  stage: e2e
    - name: mongo:4.2
    - name: mybackend
    - cd src
    - yarn
    - ... 

In the scenario above, ‘mybackend’ service waits for mongo to come up. but it never sees it.
I have tried calling Mongo by:

  • mongo:27017
  • localhost:27017

tried with FF_NETWORK, without it, aliasing the services, and so many other things I don’t even recall them…

I am on gitlab 13.2

gitlab-runner version 13.3

How can I run all my backend servers needed for this task, and make them speak to each other?