Google Cloud Build - Pass environment variable for Dockerfile

Question

I´m trying to dockerize my Angular application for Cloud Run and then conditionally build it with the production or the development configuration based on an environment variable.

cloud build command:

gcloud builds submit --tag gcr.io/project-id/image-id --timeout=1200

Dockerfile:

FROM node:14

WORKDIR usr/src/app

COPY package*.json ./

RUN npm install

# Copy local code to the container
COPY . .

# Build app
RUN if [ "$ENV" = "development" ] ; then npm run build-dev:ssr ; else npm run build-prod:ssr ; fi

CMD ["npm", "run", "serve:ssr"]

At the moment, the $ENV doesn´t exist, but is there a way to pass this with the gcloud build submit command?

Answer 1

You can't pass build argument as you do with docker build command. To achieve this, you need to create a simple Cloud Build file

steps:
  - name: 'gcr.io/cloud-builders/docker'
    args: [ 'build', '-t', 'gcr.io/project-id/image-id', '--build-arg=ENV=$_MY_VARIABLE', '.' ]
  # push the container image to Container Registry
  - name: 'gcr.io/cloud-builders/docker'
    args: ['push', 'gcr.io/project-id/image-id']
images:
  - 'gcr.io/project-id/image-id'
timeout: 1200s
substitutions:
  _MY_VARIABLE: default value if not passed in the build command

And run it like this

gcloud builds submit --substitutions=_MY_VARIABLE=specific_value

Answer 2

Adding on Guillaume Blaquiere's answer

Do not forget to add the ARG VAR_NAME in the Dockerfile (it is like a placeholder waiting for the --build-arg input). Adding only the '--build-arg=ENV=$_MY_VARIABLE' argument in the Cloud Build YAML file will not be enough for you to access the variable from the Dockerfile itself since you are giving an input to a placeholder that does not exist.