Communication between multiple docker-compose projects

Question

I have two separate docker-compose.yml files in two different folders:

• ~/front/docker-compose.yml
• ~/api/docker-compose.yml

How can I make sure that a container in front can send requests to a container in api?

I know that --default-gateway option can be set using docker run for an individual container, so that a specific IP address can be assigned to this container, but it seems that this option is not available when using docker-compose.

Currently I end up doing a docker inspect my_api_container_id and look at the gateway in the output. It works but the problem is that this IP is randomly attributed, so I can't rely on it.

Another form of this question might thus be:

• Can I attribute a fixed IP address to a particular container using docker-compose?

But in the end what I'm looking after is:

• How can two different docker-compose projects communicate with each other?

Answer 1

You just need to make sure that the containers you want to talk to each other are on the same network. Networks are a first-class docker construct, and not specific to compose.

# front/docker-compose.yml
version: '2'
services:
  front:
    ...
    networks:
      - some-net
networks:
  some-net:
    driver: bridge

...

# api/docker-compose.yml
version: '2'
services:
  api:
    ...
    networks:
      - front_some-net
networks:
  front_some-net:
    external: true

Note: Your app’s network is given a name based on the “project name”, which is based on the name of the directory it lives in, in this case a prefix front_ was added

They can then talk to each other using the service name. From front you can do ping api and vice versa.