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I try to set variables in my `docker-compose.yml` file in a separate `PORTAL_ENVIRONMENT.env` file
I don't know, what I am doing wrong.
I have this output:

WARNING: The POSTGRES_DB variable is not set. Defaulting to a blank string.
WARNING: The POSTGRES_USER variable is not set. Defaulting to a blank string.
WARNING: The POSTGRES_PASSWORD variable is not set. Defaulting to a blank string.
WARNING: The HOST variable is not set. Defaulting to a blank string.
WARNING: The PORT2 variable is not set. Defaulting to a blank string.
WARNING: The PORT3 variable is not set. Defaulting to a blank string.
WARNING: The PORT1 variable is not set. Defaulting to a blank string.

docker-compose.yml looks like this:

  client_app:
    env_file:
      - PORTAL_ENVIRONMENT.env
    image: 'client:latest'
    build:
      context: ./
    container_name: client
    depends_on:
      - db
    environment:
      - SPRING_DATASOURCE_URL=jdbc:postgresql://db:5432/${POSTGRES_DB}
      - SPRING_DATASOURCE_USERNAME=${POSTGRES_USER}
      - SPRING_DATASOURCE_PASSWORD=${POSTGRES_PASSWORD}
      - SPRING_JPA_HIBERNATE_DDL_AUTO=update
      - HOST_NAME=${HOST}
      - CREDIT_POST=${PORT1}
      - PRODUCT_POST=${PORT3}
    ports:
      - ${PORT2}:8080

(there are 3 separate modules,every looks almost the same)

PORTAL_ENVIRONMENT.env looks like this:

HOST=localhost

PORT1=8089
PORT2=8090
PORT3=8091

POSTGRES_DB=create_credit
POSTGRES_USER=user
POSTGRES_PASSWORD=pass123

I run it with:

sudo docker-compose up --force-recreate --build

Answers

When specifying your service's environment, you want those environment variables (HOST, POSTGRES_DB, etc) to be accessible to docker-compose at the time that it parses your docker-compose file. To do that, you should put them in a file called just .env. (Alternatively, if they are set in your shell environment at the time you run docker-compose, that is okay too, but you probably want to be keeping them in a .env file.)

Instead, you're trying to use env_file: in the docker-compose file. That specifies that the service that uses the env_file should look in that file and then update its own environment with that information. env_file is like environment:, but it looks at a file. It's just for the container to use, and docker-compose can't use it to set up how to run the container.

If you'd like to also pass variables from a .env file into a container, you can do something like one of these:

environment:
 - MY_VARIABLE=${VARIABLE_IN_MY_ENV_FILE}
 - MY_VARIABLE_SAFER=${VARIABLE_IN_MY_ENV_FILE:?err}

(the ?err will cause the startup to fail if the environment variable is not set, which is a nice trick.)

If you want the .env file used by docker-compose to not be named .env (maybe you are fond of the name you already have for some reason), docker-compose also has its own --env-file command-line option which you can use to specify the path of the .env file to use.

If you're still curious or confused you could also check out the docker-compose Environment Variables documentation page - that one talks about both environment-setting for docker-compose and for containers, all in the same webpage.