Cloud Build env variables not passed to Django app on GAE

Question

I have a Django app running on Google AppEngine Standard environment. I've set up a cloud build trigger from my master branch in Github to run the following steps:

steps:
  - name: 'python:3.7'
    entrypoint: python3
    args: ['-m', 'pip', 'install', '--target', '.', '--requirement', 'requirements.txt']
  - name: 'python:3.7'
    entrypoint: python3
    args: ['./manage.py', 'collectstatic', '--noinput']
  - name: 'gcr.io/cloud-builders/gcloud'
    args: ['app', 'deploy', 'app.yaml']
    env:
    - 'SHORT_SHA=$SHORT_SHA'
    - 'TAG_NAME=$TAG_NAME'

I can see under the Execution Details tab on Cloud Build that the variables were actually set.

The problem is, SHORT_SHA and TAG_NAME aren't accessible from my Django app (followed instructions at https://cloud.google.com/cloud-build/docs/configuring-builds/substitute-variable-values#using_user-defined_substitutions)! But if I set them in my app.yaml file with hardcoded values under env_variables, then my Django app can access those hardcoded values (and the values set in my build don't overwrite those hardcoded in app.yaml).

Why is this? Am I accessing them/setting them incorrectly? Should I be setting them in app.yaml somehow?

I even printed the whole os.environ dictionary in one of my views to see if they were just there with different names or something, but they're not present in there.

Answer 1

Not the cleanest solution, but I used this medium post as a guidance to my solution. I hypothesize that runserver command isn't being passed those env variables, and that those variables are only used for the app deploy command.

1. Write a Python script to dump the current environment variables in a .env file in project dir
2. In your settings file, read env variables from the .env file (I used django-environ library for this)
3. Add a step to cloud build file that runs your new Python script and pass env variables in that step (you're essentially dumping these variables into a .env file in this step)

  - name: 'python:3.7'
    entrypoint: python3
    args: ['./create_env_file.py']
    env:
    - 'SHORT_SHA=$SHORT_SHA'
    - 'TAG_NAME=$TAG_NAME'

4. Set the variables through Substitution Variables section in Edit Trigger page in Cloud Build
5. Now your application should have these env variables when app deploy happens