How to connect NATS server to NodeJS app in Docker

Question

I have a node app which connects to NATS server. Below is my docker-compose.yml for both the servers.

    version: "3"
    services:
      app:
        image: node:12.13.1
        volumes:
          - ./:/app
        working_dir: /app
        depends_on:
          - mongo
          - nats
        environment:
          NODE_ENV: development
        ports:
          - 3000:3000
        command: npm run dev
      mongo:
        image: mongo
        expose:
          - 27017
        volumes:
          - ./data/db:/data/db
      nats:
        image: 'nats:2.1.2'
    #    entrypoint: "/gnatsd -DV"
    #    entrypoint: "/nats-server -p 4222 -m 8888 "
        expose:
          - "4222"
        ports:
          - "8222:8222"
        hostname: nats-server

    app.post('/pets', function(req, res, next) {
      let nats = NATS.connect('nats://nats-server:4222');
      nats.publish('foo', 'Hello World!');
      res.json({ stats: 'success' });
    });

The above nodejs snippet gives me:

NatsError: Could not connect to server: Error: getaddrinfo ENOTFOUND nats-server

If I use let nats = NATS.connect() it gives me:

NatsError: Could not connect to server: Error: connect ECONNREFUSED 127.0.0.1:4222

Kindly throw me some ideas on how to resolve this issue. Thanks.

Answer 1

let nats = NATS.connect('nats://nats:8222');

you need to use the name of the container, and attach the internal port