Cannot connect to MongoDB via node.js in Docker - node.js

Question

My node.js express app cannot connect to the MongoDB in a Docker. I'm not that familiar with Docker.
node.js connection:
import mongodb from 'mongodb';
...
mongodb.MongoClient.connect('mongodb://localhost:27017', ... );
Dockerfile:
FROM node:argon
RUN mkdir /app
WORKDIR /app
COPY package.json /app
RUN npm install
COPY . /app
EXPOSE 3000
CMD ["npm", "start"]
docker-compose.yml
version: “2”
services:
web:
build: .
volumes:
— ./:/app
ports:
— “3000:3000”
links:
— mongo
mongo:
image: mongo
ports:
— “27017:27017”
Build command: docker build -t NAME .
Run command: docker run -ti -p 3000:3000 NAME
Connection error:
[MongoError: failed to connect to server [localhost:27017] on first connect [MongoError: connect ECONNREFUSED 127.0.0.1:27017]]
name: 'MongoError',
message: 'failed to connect to server [localhost:27017] on first connect [MongoError: connect ECONNREFUSED 127.0.0.1:27017]'

Answer 1

Try:
mongodb.MongoClient.connect('mongodb://mongo:27017', ... );
Change your docker-compose.yml:
version: "2"
services:
web:
build: .
volumes:
- ./:/app
ports:
- "3000:3000"
links:
- mongo
mongo:
image: mongo
ports:
- "27017:27017"
And use some docker compose commands:
docker-compose down
docker-compose build
docker-compose up -d mongo
docker-compose up web

Answer 2

Try this.
When using linked docker containers you should use the name of the container in this case for example your connection to mongodb should be mongodb.MongoClient.connect('mongodb://mongo:27017', ... ); instead of mongodb.MongoClient.connect('mongodb://localhost:27017', ... );. The reason for changing it to mongo is because you used the links attribute to mongo in your docker-compose.yml. That would result to a hostname of mongo in your /etc/hosts of the web docker container. Reference linking-containers.
The docker-compose.yml seems to be lacking an indention. On the mongo attribute should be the same level as web.
version: '2'
services:
web:
build: .
volumes: ['./:/app']
ports: [ '3000:3000' ]
links: [ mongo ]
mongo:
image: mongo
ports: [ '27017:27017' ]
I tried your configuration using my docker what Ive done is update docker-compose.yml then I docker-compose build then docker-compose up. Logs of my local run

Answer 3

I am not sure if you still have this question, but the datasources.json should be:
"host": "mongo"
rather than "localhost".
In my logs I see:
mongo | NETWORK [listener] connection accepted from 172.22.0.3:47880 #1 (1 connection now open)
As you can see, docker compose will NAT mongo to another V-LAN. The IP address 172.22.0.0 is an internal IP address used by the daemon to route a docker-compose image. So localhost is now not in the game.
At least, it works for me.
datasources.json
"mongoDS": {
"host": "mongo",
"port": 27017,
...

Answer 4

in my case works like this :
just link to the container from the command line. db is my up database container
sudo docker run -it --link db:db1 --publish 4000-4006:4000-4006 --name backend backend:latest