Unable to start multiple containers with the same port

[strangiato]

When attempting to start two services that both leverage the same port on a container podman-compose fails where docker-compose starts successfully.

The following is a simple compose file that demonstrates the issue:

version: "3"
services:
  web1:
    image: nginx
    ports:
    - "8080:80"
  web2:
    image: nginx
    ports:
    - "8081:80"

In docker-compose the two containers are started in a separate networking space and exposed on the host with the host port. In podman-compose it appears to create a single pod and all containers share the pods networking space.

Since default behavior in docker-compose is to not share the networking space, I would recommend that each service be created in it's own pod by default and the services only share a pod by exception.

One possible way to define this would be something like this:

version: "3"
services:
  web1:
    pod: "web-with-sidecar"
    image: nginx
    ports:
    - "8080:80"
  web1-sidecar:
    pod: "web-with-sidecar"
    image: sidecar
    ports:
    - "8181:8080"
  web2:
    image: nginx
    ports:
    - "8081:80"

This would allow podman-compose to maintain backwards compatibility with docker-compose and allow a new way to define pods with a shared networking layer.

[rpodgorny]

dupe? https://github.com/containers/podman-compose/issues/224