Connect to a PostgreSQL database on a Docker container

Question

I want to run an application with a PostgreSQL database and a REST API powered by Django on separate Docker containers. So far the API has been running on Docker connecting to a SQLite database, but I'm having trouble now that I want to connect to a PostgreSQL database instead. Docker's `docker-compose.yml` file: ``` version: '2' services: postgres: image: postgres api: build: . command: bash -c "python manage.py migrate && python manage.py runserver 0.0.0.0:1337" volumes: - .:/usr/src/app ports: - "1337:1337" depends_on: - postgres ``` Django's `settings.py` (using the default settings which the base `postgres` image works with according to the documentation): ``` DATABASES = { 'default': { 'ENGINE': 'django.db.backends.postgresql', 'NAME': 'wgomanager', 'USER': 'postgres', 'PASSWORD': 'mysecretpassword', 'HOST': 'localhost', 'PORT': '5432', } } ``` When I launch the application with `docker-compose up` eventually this error is thrown: ``` api_1 | connection = Database.connect(**conn…

Accepted Answer

When using docker-compose, you "discover" services via hostname. Your database service is defined with label postgres. Use it as a hostname in your application cofiguration.

Also password and DB name must be in sync with your app config. This is done via environment variables for postgres service:

```
services:
  postgres:
    environment:
      - POSTGRES_PASSWORD: "mysecretpassword"
      - POSTGRES_DB: "wgomanager"
  # rest of docker-compose.yml
```

Reffer to image docs on how various env. vars affect service configuration.

Connect to a PostgreSQL database on a Docker container

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