how to setup the flask pymongo configuration to use it with a container with a mongo image?

Question

I made a super simple python app which I am using to learn about docker and K8s, but I am having issues with the authentication, as I get this error when the app starts:

app_1      | pymongo.errors.OperationFailure: Authentication failed., full error: {'ok': 0.0, 'errmsg': 'Authentication failed.', 'code': 18, 'codeName': 'AuthenticationFailed'}

Here is my app, I have tried with both the comment and the uncomment configuration, as I saw in this thread from SO here , but none of them works:

from flask import Flask, jsonify
from flask_pymongo import PyMongo
import os
import json_logging, logging, sys

app = Flask(__name__)

json_logging.init_flask(enable_json=True)
json_logging.init_request_instrument(app)
logger = logging.getLogger("mongodb-service")
logger.setLevel(logging.DEBUG)
logger.addHandler(logging.StreamHandler(sys.stdout))


# app.config['MONGO_HOST'] = os.environ['MONGODB_HOSTNAME']
# app.config['MONGO_DBNAME'] = os.environ['MONGODB_DATABASE']
# app.config['MONGO_USERNAME'] = os.environ['MONGODB_USERNAME']
# app.config['MONGO_PASSWORD'] =  os.environ['MONGODB_PASSWORD']
# app.config['MONGO_AUTH_SOURCE'] = 'admin'
# mongo = PyMongo(app, config_prefix='MONGO')

app.config["MONGO_URI"] = 'mongodb://' + os.environ['MONGODB_USERNAME'] + ':' + os.environ['MONGODB_PASSWORD'] + '@' + os.environ['MONGODB_HOSTNAME'] + ':27017/' + os.environ['MONGODB_DATABASE']
mongo = PyMongo(app)
db = mongo.db

@app.route('/')
def ping_server():
    return "Welcome to the second best website ever(v2) "

@app.route('/cars')
def get_stored_cars():
    _cars = db.car_tb.find()
    cars = [{"brand": car["brand"], "model": car["model"]} for car in _cars]
    return jsonify({"cars": cars})
......

I am connecting it to a mongodb container I create in my docker-compose:

version: "3.7"
services:
  app:
    container_name: cars_app
    image: latalavera/flask-app:20.1
    build: .
    environment:
      APP_ENV: "dev"
      APP_DEBUG: "False"
      MONGODB_DATABASE: cars_db
      MONGODB_USERNAME: root
      MONGODB_PASSWORD: pass
      MONGODB_HOSTNAME: mongodb-flask
    ports:
      - ${APP_PORT}:${APP_PORT}
    depends_on:
      - mongodb
    networks:
      - app_network 
  mongodb:
    container_name: cars_db
    image: mongo:4.0
    hostname: mongodb-flask
    env_file:
      - db-env-vars.env
    volumes:
      - ./init-db.js:/docker-entrypoint-initdb.d/init-db.js:ro
      - ./mongo-volume:/data/db 
    ports:
      - ${DB_PORT}:${DB_PORT}
    networks:
      - app_network 
networks:
  app_network:
    name: app_net
    driver: bridge

but I cannot figure out what is the issue after going through the documentation and several threads here in SO

Answer 1

so I found a way to make it work, I just defined the connection like this:

def get_db():
    client = MongoClient(host=os.environ['MONGODB_HOSTNAME'],
                         port=27017, 
                         username=os.environ['MONGODB_USERNAME'], 
                         password=os.environ['MONGODB_PASSWORD'],
                        authSource="admin")
    db = client[os.environ['MONGODB_DATABASE']]
    return db

then defined the variables in the env filed in the dockerfile as above