Docker mongodb connection refused on mac os when loading http://0.0.0.0:27017

Question

Browser Screenshot I have 2 docker containers running mongo:3.0.3 and python:2.7. And I have an app.py which connects to mongodb instance. In my app.py I have used port 5000 to map 27017. The app.py runs fine but when I visit http://0.0.0.0:5000 this connection refused error comes on terminal.

172.17.0.1 - - [01/Jul/2018 10:01:32] "GET / HTTP/1.1" 500 -
Traceback (most recent call last):
  File "/usr/local/lib/python2.7/site-packages/flask/app.py", line 1836, in __call__
return self.wsgi_app(environ, start_response)
  File "/usr/local/lib/python2.7/site-packages/flask/app.py", line 1820, in wsgi_app
    response = self.make_response(self.handle_exception(e))
  File "/usr/local/lib/python2.7/site-packages/flask/app.py", line 1403, in handle_exception
    reraise(exc_type, exc_value, tb)
  File "/usr/local/lib/python2.7/site-packages/flask/app.py", line 1817, in wsgi_app
    response = self.full_dispatch_request()
  File "/usr/local/lib/python2.7/site-packages/flask/app.py", line 1477, in full_dispatch_request
    rv = self.handle_user_exception(e)
  File "/usr/local/lib/python2.7/site-packages/flask/app.py", line 1381, in handle_user_exception
    reraise(exc_type, exc_value, tb)
  File "/usr/local/lib/python2.7/site-packages/flask/app.py", line 1475, in full_dispatch_request
    rv = self.dispatch_request()
  File "/usr/local/lib/python2.7/site-packages/flask/app.py", line 1461, in dispatch_request
    return self.view_functions[rule.endpoint](**req.view_args)
  File "/pythonApp/app.py", line 16, in form
    if posts.count()!=0:
  File "/usr/local/lib/python2.7/site-packages/pymongo/collection.py", line 1023, in count
    return self._count(cmd)
  File "/usr/local/lib/python2.7/site-packages/pymongo/collection.py", line 985, in _count
    with self._socket_for_reads() as (sock_info, slave_ok):
  File "/usr/local/lib/python2.7/contextlib.py", line 17, in __enter__
    return self.gen.next()
  File "/usr/local/lib/python2.7/site-packages/pymongo/mongo_client.py", line 699, in _socket_for_reads
    with self._get_socket(read_preference) as sock_info:
  File "/usr/local/lib/python2.7/contextlib.py", line 17, in __enter__
    return self.gen.next()
  File "/usr/local/lib/python2.7/site-packages/pymongo/mongo_client.py", line 663, in _get_socket
    server = self._get_topology().select_server(selector)
  File "/usr/local/lib/python2.7/site-packages/pymongo/topology.py", line 121, in select_server
address))
  File "/usr/local/lib/python2.7/site-packages/pymongo/topology.py", line 97, in select_servers
    self._error_message(selector))
ServerSelectionTimeoutError: localhost:27017: [Errno 111] Connection refused

I can't find any .conf files as this is a container. Any idea on how to get this fixed? :/

my docker image https://hub.docker.com/r/sizijay/dockerexercise/ see the long description for dockerfile

Answer 1

Run the Mongo container:

$ docker run -d -p "27017:27017" mongo 

In your app.py, use pymongo Connection.

from pymongo import Connection
c = Connection(host=0.0.0.0, port=27017)
c.test_database

Note: the host is 0.0.0.0.

Run your container:

$ docker run -d -p 5000:5000 sizijay/dockerexercise

If you use localhost as your host, pymongo will be looking inside the container from which is running (i.e. sizijay/dockerexercise). When you use 0.0.0.0, the connection will be to your host machine, which now has port 27017 bound to 27017 inside your mongo container.

---

A better alternative would be to use docker-compose to link your containers.

In this case, you need to create a file: docker-compose.yml:

version: '3'

services:
  db:
    image: mongo
    ports:
      - "27017:27017"

  myapp:
    image: sizijay/dockerexercise
    ports:
      - "5000:5000"
    links:
      - db
    depends_on:
      - db

In your app.py, use pymongo Connection.

from pymongo import Connection
c = Connection(host='db', port=27017)
c.test_database

Note: the host is db.

Now your host is not inside your app container, but inside the db service (i.e. the mongo container).

You can run docker-compose by:

$ docker build -t sizijay/dockerexercise .
$ cd location_of_docker-compose.yml
$ docker-compose up