Docker, Flask, SQLAlchemy: ValueError: invalid literal for int() with base 10: 'None'

Question

I have a flask app that can be initialized successfully and connects to Postgresql database. However, when i try to dockerize this app, i get the below error message. "SQLALCHEMY_DATABASE_URI" is correct and i can connect to it, so i can't figure where I have gone wrong.

docker-compose logs

app_1       |   File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/engine/url.py", line 60, in __init__
app_1       |     self.port = int(port)
app_1       | ValueError: invalid literal for int() with base 10: 'None'

Postgres database connects successfully in Docker container

postgres_1  | LOG:  database system is ready to accept connections

config.py

from os import environ
import os

RDS_USERNAME = environ.get('RDS_USERNAME')
RDS_PASSWORD = environ.get('RDS_PASSWORD')
RDS_HOSTNAME = environ.get('RDS_HOSTNAME')
RDS_PORT = environ.get('RDS_PORT')
RDS_DB_NAME = environ.get('RDS_DB_NAME')

SQLALCHEMY_DATABASE_URI = "postgresql+psycopg2://{username}:{password}@{hostname}:{port}/{dbname}"\
                          .format(username = RDS_USERNAME, password = RDS_PASSWORD, \
                           hostname = RDS_HOSTNAME, port = RDS_PORT, dbname = RDS_DB_NAME)

flask_app.py (entry point)

def create_app():
    app = Flask(__name__, static_folder="./static", template_folder="./static")
    app.config.from_pyfile('./app/config.py', silent=True)

    register_blueprint(app)
    register_extension(app)

    with app.app_context():
        print(db) -> This prints the correct path for SQLALCHEMY_DATABASE_URI
        db.create_all()
        db.session.commit()
    return app

def register_blueprint(app):
    app.register_blueprint(view_blueprint)
    app.register_blueprint(race_blueprint)


def register_extension(app):
    db.init_app(app)
    migrate.init_app(app)


app = create_app()

if __name__ == '__main__':
    app.run(host='0.0.0.0', port=8080, debug=True)

Dockerfile

FROM ubuntu

RUN apt-get update && apt-get -y upgrade

RUN apt-get install -y python-pip && pip install --upgrade pip

RUN mkdir /home/ubuntu

WORKDIR /home/ubuntu/celery-scheduler

ADD requirements.txt /home/ubuntu/celery-scheduler/

RUN pip install -r requirements.txt

COPY . /home/ubuntu/celery-scheduler

EXPOSE 5000

CMD ["python", "flask_app.py", "--host", "0.0.0.0"]

docker-compose.yml

version: '2' 

services:
  app:
    restart: always
    build: 
      context: .
      dockerfile: Dockerfile
    volumes:
      - .:/app
    depends_on:
      - postgres

  postgres:
    restart: always
      image: postgres:9.6
    environment:
      - POSTGRES_USER=${RDS_USERNAME}
      - POSTGRES_PASSWORD=${RDS_PASSWORD}
      - POSTGRES_HOSTNAME=${RDS_HOSTNAME}
      - POSTGRES_DB=${RDS_DB_NAME}
    ports:
      - "5432:5432"

Answer 1

You need to set environment variables RDS_USERNAME, RDS_PASSWORD, RDS_HOSTNAME, RDS_PORT , and RDS_DB_NAME in Dockerfile with ENV key value, for example

ENV RDS_PORT 5432