cloudbuild-network-experiment

Minimal reproducible repo for studying sharing of network, in Cloud Build CI.

The goal:

• to be able to launch background servers
• ..and use them in following Cloud Build steps

TL;DR

Solved this, for my use case (running Firebase Emulators within Cloud Build run, and then accessing them in later steps).

The solution is based on wrapping whatever tools you want to use (e.g. npm) into a Docker (or Docker Compose) step. This is acceptable to the author.

Found clues

Cloud Build documentation states:

Each build step is run with its container attached to a local Docker network named cloudbuild. This allows build steps to communicate with each other and share data.

However, it does not give a sample on how this is done!

The only source found by the author is: Communicate between two containers in Google cloud build (SO)

Does it work, in 2021???

Requirements

• gcloud installed, and a project activated (with CloudBuild APIs enabled)

Steps

$ gcloud builds submit --config=ci/cloudbuild.yaml

Expected / wished for

• Port 6768 would respond with 200; the Cloud Build run will pass

Actual

Could not resolve host: abc

Conclusion

Studying the said SO entry 3-5 times, and trying different approaches the author concludes (Sep 2021):

1. Wasn't able to:

• get a "native" Cloud Build step, following Docker Compose up -d, to reach such service

In particular, the mention of cloudbuild network in the Cloud Build docs is confusing. There are no samples, on how it would be used.

2. Was able to:

   • listen to the server, from cloudbuild.yaml, if the step is wrapped like this:

     # Listen from Docker. Works
   

• name: docker args: ['run', '--network', 'workspace_default', 'gcr.io/cloud-builders/curl', 'abc:6768']

Note that the name of the network is `workspace_default`, derived from the working directory of Cloud Build runs (`/workspace`).


This is enough.

It's a bit clumsy, but means that *any* steps can be declared within the `cloudbuild.yaml`, without help from the Docker Compose file. This is one of the goals of the author, to keep CI definitions away from cluttering the developer's folder.