Docker-compose: bind Celery to Postgres database

Question

My Docker app runs with Flask as backend and Celery as an asyncronous task manager. Task results are then dumped in a SQLalchemy database owned by Postgres.

However, I am not being able to make Celery interact with Postgres.

Configuration:

docker-compose-dev.yml

  web:
    build:
      context: ./services/web
      dockerfile: Dockerfile-dev
    volumes:
      - './services/web:/usr/src/app' 
    ports:
      - 5001:5000
    environment:
      - FLASK_ENV=development
      - APP_SETTINGS=project.config.DevelopmentConfig
      - DATABASE_URL=postgres://postgres:postgres@web-db:5432/web_dev 
      - DATABASE_TEST_URL=postgres://postgres:postgres@web-db:5432/web_test
      - SECRET_KEY=my_precious  
    depends_on:  
      - web-db
      - redis

  web-db:  
    build:
      context: ./services/web/project/db
      dockerfile: Dockerfile
    ports:
      - 5435:5432
    environment:
      - POSTGRES_USER=postgres
      - POSTGRES_PASSWORD=postgres

  celery:
    image: dev3_web
    restart: always
    volumes:
     - ./services/web:/usr/src/app
     - ./services/web/celery_logs:/usr/src/app/celery_logs

    command: celery worker -A celery_worker.celery --loglevel=DEBUG --logfile=celery_logs/celery.log -Q cache
    environment:
     - CELERY_BROKER=redis://redis:6379/0
     - CELERY_RESULT_BACKEND=redis://redis:6379/0
    depends_on:
     - web
     - redis
    links:
     - redis:redis
     - web-db

  redis:
    image: redis:5.0.3-alpine
    restart: always
    expose:
      - '6379'
    ports:
      - '6379:6379'

  monitor:
    image: dev3_web
    ports:
      - 5555:5555
    command:  flower -A celery_worker.celery --port=5555 --broker=redis://redis:6379/0
    depends_on:
      - web
      - redis

Log:

celery_1| Neither SQLALCHEMY_DATABASE_URI nor SQLALCHEMY_BINDS is set. Defaulting SQLALCHEMY_DATABASE_URI to "sqlite:///:memory:".

How do I bind Celery tasks to my Postgres database?

Answer 1

celery_1   | Neither SQLALCHEMY_DATABASE_URI nor SQLALCHEMY_BINDS is set. Defaulting SQLALCHEMY_DATABASE_URI to "sqlite:///:memory:".

suggests that the error from your celery container, which missing the environment valuable setup, you might need DATABASE_URL setup for it which created based on dev3_web.

changes need apply to your docker-compose-dev.yml:

  celery:
    image: dev3_web
    restart: always
    volumes:
     - ./services/web:/usr/src/app
     - ./services/web/celery_logs:/usr/src/app/celery_logs

    command: celery worker -A celery_worker.celery --loglevel=DEBUG --logfile=celery_logs/celery.log -Q cache
    environment:
     - CELERY_BROKER=redis://redis:6379/0
     - CELERY_RESULT_BACKEND=redis://redis:6379/0
     - APP_SETTINGS=project.config.DevelopmentConfig
     - DATABASE_URL=postgres://postgres:postgres@web-db:5432/web_dev 
    depends_on:
     - web
     - redis
    links:
     - redis:redis
     - web-db