Will docker-compose allow mapping a port to two ports or do I need an ambassador?

Question

Suppose I have an application that listens on 8888 - other parts of the application want to continue to access it on 8888 - but the external users need to access it at a port range above 50000 - eg 50888.

What I'd like to do in my docker-compose.yml is:

ports:
  - "8888:8888"
  - "50888:8888"

Will this work?

My other alternative is to add an ambassador in there like this:

blah:
  image: blah:6
  ports:
    - "8888:8888"
  container_name: blah
  networks:
    default: {}
blah_ambassador:
  image: svendowideit/ambassador
  links:
    - blah
  ports:
    - "50888:8888"
  environment:
    - BLAH_PORT_8888_TCP:tcp://blah:8888 
  container_name: ops_ambassador
  networks:
    default: {}

My question is: Will docker-compose allow mapping a port to two ports or do I need an ambassador?

Answer 1

Some time ago, docker-compose used a dictionary to store the mapping ports and the key was the internal port, so one value overrode the other.

This was fixed here using a list. So, currently, docker-compose allows mapping an internal port to two ports. Maybe you are using an older docker-compose version.

Example:

→ docker-compose -v
docker-compose version 1.8.0, build f3628c7

Docker-compose file content (docker-compose.yml):

backend:
  image: your_image
  ports:
    - 3000:3000
    - 8888:3000

docker inspect command: docker inspect your_container_id

"Ports": {
            "3000/tcp": [
                {
                    "HostIp": "0.0.0.0",
                    "HostPort": "8888"
                },
                {
                    "HostIp": "0.0.0.0",
                    "HostPort": "3000"
                }
            ]
        },