Unable to curl from one container to another

Question

I have two containers in one docker-compose.yml. Both are on same on same network. I have added the dependency using "depends_on", I am able to ping the other container, but curl is not working.

version: "2.1"
services:
    web:
            restart: always
            build:
                    context: .
                    dockerfile: web.dockerfile
            ports:
                    - "9000:8080"
            expose:
                    - "8080"

            networks:
                    - test

    nginx_web:
            restart: always
            build:
                    context: .
                    dockerfile: nginx_web.dockerfile
            ports:
                    - "8100:80"
            expose:
                    - "80"
            depends_on:
                    - web
            networks:
                    - test
    networks:
            test:

When I am trying ping from nginx_web container to web, it is working fine. But the curl isn't working. I am getting

curl: (7) Failed to connect to 172.28.0.7 port 8080: Connection refused

And when I am doing curl from the host machine directly to web at port 9000, it is working fine.

Answer 1

In your django app, change it from listening on 127.0.0.1 to listen on all interfaces with 0.0.0.0. Docker containers get their own network namespace, so you can't access another container's loopback interface.

Also, your ports do not match. Django is responding on 9000, so from container to container, you need to use port 9000. The mapping to your published port only happens on the docker host. And exposing a port really doesn't do anything for this use case.

Lastly, from your host, you have the ports reversed. It's the port on the host followed by the port inside the container. So "8080:9000".