How to swap env file for another docker service-CodePudding

I have a docker-compose.yml

services:
  nextjs:
    container_name: next_app
    build:
      context: ./
    restart: on-failure
    command: npm run dev
    volumes:
      - ./:/app
      - /app/node_modules
      - /app/.next
    ports:
      - "3000:3000"
  cypress:
    image: "cypress/included:9.4.1"
    depends_on:
      - next_app
    environment:
      - CYPRESS_baseUrl=http://nextjs:3000
    working_dir: /e2e
    volumes:
      - ./e2e:/e2e

I want to change env_file for next_app from cypress service. I found solution like this

cypress:
    image: "cypress/included:9.4.1"
    depends_on:
      - next_app
    environment:
      - CYPRESS_baseUrl=http://nextjs:3000
    working_dir: /e2e
    volumes:
      - ./e2e:/e2e
    next_app:
      env_file: .env.test

But this solution does not work. Is it even possible ?

CodePudding user response：

Hello Rajesh Koothropali! Try something like cp .env #docker/.env

CodePudding user response：

No. In Compose (or Docker, or even more generally in Linux/Unix) there is no way for one container (process) to specify environment variables for another.

You can think of a docker-compose.yml file as a set of instructions only for running containers. If you need a specific set of containers for a specific context – you don't normally need to run Cypress in production, but this is an integration-test setup – it's fine to write a separate Compose file just for that setup.

# docker-compose.cypress.yml
# Used only for integration testing
version: '3.8'
services:
  nextjs:
    build: .
    restart: on-failure
    ports:
      - "3000:3000"
    env_file: .env.test # <-- specific to this test-oriented Compose file
  cypress:
    build: ./e2e
    depends_on:
      - nextjs
    environment:
      - CYPRESS_baseUrl=http://nextjs:3000

docker-compose -f docker-compose.cypress.yml up --build

This can also be a case where using multiple Compose files together can be a reasonable option. You can define a "standard" Compose setup that only defines the main service, and then an e2e-test Compose file that adds the Cypress container and the environment settings.

# docker-compose.yml
version: '3.8'
services:
  nextjs:
    image: registry.example.com/nextjs:${NEXTJS_TAG:-latest}
    restart: on-failure
    ports:
      - '3000:3000'

# docker-compose.e2e.yaml
version: '3.8'
services:
  nextjs:
    # These add to the definitions in the base `docker-compose.yml`
    build: .
    env_file: .env.test
  cypress:
    # This is a brand new container for this specific setup
    depends_on: [nextjs]
    et: cetera # copy from question or previous Compose setup

docker-compose \
  -f docker-compose.yml \
  -f docker-compose.e2e.yml \
  up --build