[FIXED] How to set Environment Variables on Flask/MongoDB on AWS ECS?

Issue

I have a flask application that runs with MongoDB.

Locally, When I build and run the container using the following below, the app runs perfectly good locally.

docker-compose build
docker-compose up

These are the created containers:

/application$ docker ps -a
CONTAINER ID        IMAGE               COMMAND                  CREATED             STATUS              PORTS                           NAMES
9e054b28bb46        application_web     "/bin/sh -c 'python …"   38 seconds ago      Up 37 seconds       0.0.0.0:80->80/tcp, 27017/tcp   application_web_1
2a19a8e9a267        mongo:3.0.2         "/entrypoint.sh mong…"   39 seconds ago      Up 38 seconds       0.0.0.0:27017->27017/tcp        application_db_1

I have the following in my app.py:

MONGODB_HOST = os.environ['DB_PORT_27017_TCP_ADDR']
MONGODB_PORT = 27017

app = Flask(__name__)
bootstrap = Bootstrap(app)
client = MongoClient(MONGODB_HOST, MONGODB_PORT)

docker-compose.yml

web:
  build: .
  command: python -u app.py
  ports:
    - "80:80"
  volumes:
    - .:/project
  environment:
    MONGODB_HOST: db
  links:
      - db

db:
  image: mongo:3.4
  command: mongod
  ports:
    - "27017:27017"

Dockerfile

FROM python:3.6.1-alpine

MAINTAINER [email protected]

WORKDIR /project

ADD . /project

RUN pip install -r requirements.txt

EXPOSE 80

EXPOSE 27017

CMD ["mongod"]

ENV NAME Cheppers_DevOps_Challenge

ENTRYPOINT python app.py

The problem that I am facing, after pushing the images into AWS ECS then I create the cluster with given pushed repository for the container image, I always get this error in the task definition logs:

2019-10-08 14:19:02
MONGODB_HOST = os.environ['DB_PORT_27017_TCP_ADDR']
KeyError: 'DB_PORT_27017_TCP_ADDR'

Solution

I suggest you to change mongo host :

MONGODB_HOST = "db"

this os.environ['DB_PORT_27017_TCP_ADDR'] will use the IP address of the container which you do not need since compose will handle that for you using the service names.

I think AWS handle the IP address in different way that is not a dict anymore ("KeyError")

Answered By - LinPy