How to connect nodeJS docker container to mongoDB

Question

I have problems to connect a nodeJS application which is running as a docker container to a mongoDB. Let me explain what I have done so far:

$ docker ps

CONTAINER ID    IMAGE        COMMAND                  CREATED        STATUS        PORTS        NAMES
3a3732cc1d90    mongo:3.4    "docker-entrypoint..."   3 weeks ago    Up 3 weeks    27017/tcp    mongo_live

As you can see, there is already a mongo docker container running.

Now I'm running my nodeJS application docker container (which is a build from meteorJS):

$ docker run -it 0b422defbd59 /bin/bash

In this docker container I want to run the application by running:

$ node main.js

Now I'm getting the error

Error: MONGO_URL must be set in environment

I already tried to set MONGO_URL by setting:

ENV MONGO_URL mongodb://mongo_live:27017/

But this doesn't work:

MongoError: failed to connect to server [mongo_live:27017] on first connect

So my question is how to connect to a DB, which is - as far as I understand - 'outside' of the running container. Alternativly how do I set up a new DB to this container?

Answer 1

There are couple of ways to do it.

• run your app in the same network as your mongodb:

  docker run --net container:mongo_live your_app_docker_image
  
  # then you can use mongodb in your localhost
  $ ENV MONGO_URL mongodb://localhost:27017/
  

• Also you can link two containers:

  docker run --link mongo_live:mongo_live you_app_image ..
  # Now mongodb is accessible via mongo_live
  

• use mongodb container ip address:

  docker inspect -f '{{.NetworkSettings.IPAddress}}' mongo_live
  # you will get you container ip here
  
  $ docker run -it 0b422defbd59 /bin/bash
  # ENV MONGO_URL mongodb://[ip from previous command]:27017/
  

• You can bind your mongodb port to your host and use host's hostname in your app

• You can use docker network and run both apps in the same network

• You could pass --add-host mongo_live:<ip of mongo container> to docker run for your application and then use mongo_live for mongodb url

• You can also use docker compose to make your life easier ;)

...