如何将Docker容器端口映射到其他号码-但不在主机上

Question

For testing purposes I would like to run a cluster of three containers, each running the same service on port 7600. Those containers should reside in one network and could theoretically access each other as host1:7600 , host2:7600 and host3:7600 .

However I want to 'emulate' an external port mapping, such that the service of each container is still bound to port 7600 but that the services can acess each other by maped (different) ports like host1:8881 , host2:8882 and host3:8883 .

How can I do that as easily as possible - preferred within a Docker Compose setup.

The reasoning is that I want to test how the service will behave with a configuration of three physical hosts running that service and mapped its port to an arbitrary external port.

Following some edits to clarify the task, after the first comments won't met the requirements (however thank you for every answer).

• I can't use VMs , as the Test is already running within VirtualBox with no ability to get nested VT-x running.
• I would neither bind the ports to the host, nor to the same IP address.

Answer 1

After further investigation I found a working solution for me.

The following Docker Compose file shows an example of the solution. It shows how to make two services accessible by an external IP and external port. The example works completely in Docker without the need to run the containers in two separate virtual machines.

The two services are by example two Nginx instances. Imagine both services should access each other by their external IP and port to form a cluster. The external IP and port are emulated by two separate busybox containers mapping the ports of the service containers to their own IP.

version: '3'

services:

  service1:
    image: nginx:latest

  service2:
    image: nginx:latest

  proxy1:
    image: busybox:latest
    command: nc -lk -p 8081 -e /bin/nc service1 80
    expose:
      - "8081"

  proxy2:
    image: busybox:latest
    command: nc -lk -p 8082 -e /bin/nc service2 80
    expose:
      - "8082"

The services service1:80 and service2:80 can access each other by their external representations proxy1:8081 and proxy2:8082