How do I configure Docker Compose to use a single password for both PostgreSQL and node-postgres?

I did a little experiment to confirm that the password wasn't being set, but apparently it is actually being set. I don't know why I'm getting that warning message though.

The experimient:

JAVASCRIPTCopied
const { Client } = pg;
const client = new Client({
  user: 'root',
  password: 'root',
  database: 'qr_orders_db',
});
await client.connect();

Apparently this doesn't throw errors when .env.local is loaded before .env in the docker compose file. Mysteries of life I guess ¯_( Ts)_/¯.

I won't mark my own answer as the accepted one for now because I want to see if someone knows how to get rid of that warning.

---

EDIT: (Actual answer)

You can rename the .env file to something different to make sure docker-compose itself doesn't load it because it loads .env by default before loading the environment files specified in the yaml file. For instance you can rename it to .environment:

YAMLCopied
env_file:
  - ./.env.local
  - ./.environment

Now the warning won't show up because docker-compose itself is not loading it because it's not present anymore.

However the problem now is that you might be working with other software that also uses .env like Nextjs. In the case of Nextjs .environment won't work so you will have to rename it to something like .env.development instead.

Alternatively you can also use @DavidMaze's solution. And because it consists of setting the COMPOSE_ENV_FILES environment variable and because you can technically set predefined environment variables like this one in the .env file, in theory you should also be able to just add COMPOSE_ENV_FILES to .env. However it won't actually work :(

Compose has two layers of environment-variable management. Compose itself uses a .env file and the host environment to do variable substitution in the Compose file, and then it uses environment: and env_file: directives to populate the per-container environment.

I'd probably set this up by writing the credentials in the .env file, and then selectively importing these into containers.

The first step is to make Compose aware of your .env.local file. I'd set a COMPOSE_ENV_FILES environment variable so that you only need to do this once. (The alternative is passing a docker-compose --env-file option every time you run any Compose command.)

BASHCopied
export COMPOSE_ENV_FILES=.env,.env.local
docker-compose up -d

Remove the env_file: settings, but add environment: blocks that set the variables to the correct values, renaming them if needed. The $VARIABLE references will come from the settings in the $COMPOSE_ENV_FILES.

YAMLCopied
services:
  db:
    image: postgres
    environment:
      POSTGRES_USER: ${DB_USER}
      POSTGRES_PASSWORD: ${DB_PASSWORD}
      POSTGRES_DB: ${DB_DATABASE}
  app:
    build: .
    environment:
      PGHOST: db
      PGUSER: ${DB_USER}
      PGPASSWORD: ${DB_PASSWORD}
      PGDATABASE: ${DB_DATABASE}

I might use the standard PostgreSQL client variable names in the .env.local file, in which case there's special Compose syntax to pass through the host-environment value.

YAMLCopied
services:
  db:
    environment:
      POSTGRES_USER: ${PGUSER}
  app:
    environment:
      PGUSER:

In the last block, $PGUSER intentionally has an empty (null) value. If you're using YAML list syntax environment: [VAR=value, VAR2=value2] then specifying just the variable name with no value (just a bare PGUSER) has the same effect.