How to use GCP service account json files in Docker - docker

Question

I am dockerizing Fastapi application which is using Firebase. I need to access service json file and I have configured my docker container as follows.
Dockerfile
FROM python:3.10-slim
ENV PYTHONUNBUFFERED 1
WORKDIR /app
# Install dependencies
COPY ./requirements.txt /requirements.txt
EXPOSE 8000
RUN pip install --no-cache-dir --upgrade -r /requirements.txt
RUN mkdir /env
# Setup directory structure
COPY ./app /app/app
COPY ./service_account.json /env
CMD ["uvicorn", "app.app:app", "--host", "0.0.0.0", "--port", "8000"]
Docker-compose file
version: "3.9"
services:
app:
build:
context: .
restart: always
environment:
- GOOGLE_APPLICATION_CREDENTIALS_CLOUDAPI=${GOOGLE_APPLICATION_CREDENTIALS_CLOUDAPI}
- GOOGLE_APPLICATION_CREDENTIALS=${GOOGLE_APPLICATION_CREDENTIALS}
volumes:
- ./env:/env
volumes:
env:
Now when I run docker-compose up -d --build the container fails with the error FileNotFoundError: [Errno 2] No such file or directory: '/env/service_account.json'. When I inspect the container I can see the ENV variable set successfully as shown "GOOGLE_APPLICATION_CREDENTIALS=/env/service_account.json",. Now why is this failing?

Answer 1

You have context: . and COPY ./service_account.json /env
But when you run the container, you have
volumes:
- ./env:/env
Meaning your service_acccount file is not in ./env folder, and is instead outside of it.
When you mount a volume, it replaces the directory inside the container, so if you need a local env folder mounted as /env in the container, then you should move your JSON file somewhere else such as /opt (COPY ./service_account.json /opt), and then set GOOGLE_APPLICATION_CREDENTIALS=/opt/service_account.json
If you don't need the whole folder, then you only need
volumes:
- ./service_account.json:/env/service_account.json:ro
Otherwise, move the JSON file into ./env on your host and change COPY ./env/service_account.json /env