Using the host ip in docker-compose

Question

I want to create a docker-compose file that is able to run on different servers.

For that I have to be able to specify the host-ip or hostname of the server (where all the containers are running) in several places in the docker-compose.yml.

E.g. for a consul container where I want to define how the server can be found by fellow consul containers.

consul:   image: progrium/consul   command: -server -advertise 192.168.1.125 -bootstrap 

I don't want to hardcode 192.168.1.125 obviously.

I could use env_file: to specify the hostname or ip and adopt it on every server, so I have that information in one place and use that in docker-compose.yml. But this can only be used to specifiy environment variables and not for the advertise parameter.

Is there a better solution?

Answer 1

docker-compose allows to use environment variables from the environment running the compose command.

See documentation at https://docs.docker.com/compose/compose-file/#variable-substitution

Assuming you can create a wrapper script, like @balver suggested, you can set an environment variable called EXTERNAL_IP that will include the value of $(docker-machine ip).

Example:

#!/bin/sh export EXTERNAL_IP=$(docker-machine ip) exec docker-compose $@ 

and

# docker-compose.yml version: "2" services:   consul:     image: consul     environment:       - "EXTERNAL_IP=${EXTERNAL_IP}"     command: agent -server -advertise ${EXTERNAL_IP} -bootstrap 

Unfortunately if you are using random port assignment, there is no way to add EXTERNAL_PORT, so the ports must be linked statically.

PS: Something very similar is enabled by default in HashiCorp Nomad, also includes mapped ports. Doc: https://www.nomadproject.io/docs/jobspec/interpreted.html#interpreted_env_vars

Answer 2

I've used docker internal network IP that seems to be static: 172.17.0.1