如何从容器内部访问正在运行的docker容器外部ip？

Question

When I deploy via docker-compose , I can run inspect on any of the containers and see the external ip.

$ docker inspect --format '{{ .NetworkSettings.IPAddress }}' parentserver
>>>172.17.0.3

My question is, if someone were to, say, git clone my repository on their local machine and run docker-compose , is it guaranteed that the IP of parentserver would be 172.17.0.3 on their machine as well?

The reason I ask is I have microservices that talk to each other via HTTP, and I currently have the IPs hardcoded inside my apps logic.

If the IP of each docker container is guaranteed to be the same no matter where it's run, this wouldn't be an issue, either way I need to find a better solution which is why I'm wondering if I can query the external IP from running docker containers from within the container?

Answer 1

Docker containers created via docker-compose are put in a shared network by default and are hooked to an embedded DNS server. This means they are linked by default. A container "A" linked to container "B" can ping container "B" by its assigned link name, by default, the container name.

Take as an example my nginx config:

version: '2'

services:
  # ... more config

  nginx:
    environment:
      API_DOMAIN:     api.mysite.com
      FRONT_DOMAIN:   'mysite.com www.mysite.com'
      ERRBIT_DOMAIN:  errbit.mysite.com
      ERRBIT_HOST:    http://errbit:8080
      PGADMIN_DOMAIN: pgadmin.mysite.com
      PGADMIN_HOST:   http://pgadmin:5050

  errbit:
    env_file: ./production/errbit.env

I've made an nginx image that accepts domains via environment vars, and the hosts are the names of other containers running in the same docker host created using this config.

https://docs.docker.com/engine/userguide/networking/