How to prevent overwriting the whole environment field while using YAML anchors

Question

I am writing my docker-compose.yml file and to avoid writing redundant lines especially for using different profiles for dev, uat, prod etc, I was using yaml anchors. Here is a sample for one of the adapters I used for uat and for dev.

Adapter:&Adapter
  image:"my-image"
  profiles:
    - uat
  environment:
    - JAVA_OPTS="${JAVA_OPTS} -Dloader.main=com.my.class"
    - SPRING_PROFILES_ACTIVE=uat
  volumes:
    - /local/path/to/logs:/logs
  depends_on:
    - some_image

Adapter-dev:
  <<: *Adapter
  profiles:
    - dev
  environment:
    - SPRING_PROFILES_ACTIVE=dev

.env file contains:

JAVA_OPTS=-Xmx3g -Xms3g

The key part is that the JAVA_OPTS is a must have in order to run properly. The JAVA_OPTS is stored in a .env file, and I append to the JAVA_OPTS variable to specify my main class. I just found out that doing it in the way above, it overwrites the environment entirely and only passes the SPRING_PROFILES_ACTIVE to my docker container's environment variables. What I expected would be that only SPRING_PROFILES_ACTIVE would be overwritten, but the JAVA_OPTS would be preserved. How can I only overwrite the SPRING_PROFILES_ACTIVE in my docker-compose.yml without overwriting the JAVA_OPTS?

Answer 1

The specific solution used was to utilise a common-services.yml file. This allowed me to only run the services with the specified profile without running the default services. What I did was to extract the default service to an additional yml file like so:

#common-services.yml:
services:
  adapter:
    image: "my-image"
    profiles: []
    environment:
      - JAVA_OPTS="${JAVA_OPTS} -Dloader.main=com.my.class"
    volumes:
      - /local/path/to/logs:/logs

and the docker compose yaml will look like:

#docker-compose.yml
version: '3.9'
services:
  adapter-uat:
    extends:
      file: common-services.yml
      service: adapter
    profiles:
      - uat
    environment:
      - SPRING_PROFILES_ACTIVE=uat
    depends_on:
      - some_image

  adapter-dev:
    extends:
      file: common-services.yml
      service: adapter
    profiles:
      - dev
    environment:
      - SPRING_PROFILES_ACTIVE=dev
    depends_on:
      - some_image