Is it possible to add dependent environment variables in Google Cloud Run? - kubernetes

Question

I would like to specify dependent environment variables on a Cloud Run service.
If the environment variables have been defined in a .env file it would look like this
DATABASE_NAME=my-database
DATABASE_USER=root
DATABASE_PASSWORD=P4SSw0rd!
DATABASE_PORT=5432
DATABASE_HOST="/socket/my-database-socket"
DATABASE_URL="user=${DATABASE_USER} password=${DATABASE_PASSWORD} dbname=${DATABASE_NAME} host=${DATABASE_HOST}"
In this example, DATABASE_URL depends on every other environment variables.
To deploy the service I run the following command:
gcloud run deploy my-service \
--image gcr.io/my-project/my-image:latest \
--region europe-west1 \
--port 80 \
--platform managed \
--allow-unauthenticated \
--set-env-vars 'DATABASE_NAME=my-database' \
--set-env-vars 'DATABASE_USER=root' \
--set-env-vars 'DATABASE_PASSWORD=P4SSw0rd!' \
--set-env-vars 'DATABASE_PORT=5432' \
--set-env-vars 'DATABASE_HOST="/socket/my-database-socket"' \
--set-env-vars 'DATABASE_URL="user=$(DATABASE_USER) password=$(DATABASE_PASSWORD) dbname=$(DATABASE_NAME) host=$(DATABASE_HOST)"'
Here is the created YAML definition of the service (some values are omitted)
apiVersion: serving.knative.dev/v1
kind: Service
metadata:
name: my-service
spec:
template:
metadata:
name: ...
spec:
containerConcurrency: 80
timeoutSeconds: 300
containers:
- image: ...
ports:
- name: http1
containerPort: 80
env:
- name: DATABASE_NAME
value: my-database
- name: DATABASE_USER
value: root
- name: DATABASE_PASSWORD
value: P4SSw0rd!
- name: DATABASE_HOST
value: /socket/my-database-socket
- name: DATABASE_URL
value: user=$(DATABASE_USER) password=$(DATABASE_PASSWORD) dbname=$(DATABASE_NAME) host=$(DATABASE_HOST)
The problem is that when the service is running, the env vars in DATABASE_URL seem not interpolated.
I read that Kubernetes supports dependent env vars but I can't figure out how to make this run in Cloud Run.
I am wondering if it is supported in Cloud Run in the end.

Answer 1

It's likely this may work in Knative open source (which uses Kubernetes to execute pods) but not on Google Cloud Run (fully hosted), which runs on a proprietary execution engine.