dynamic rails config files

.env

ODC_REDIS_SERVER_URL="redis://$(docker-service odc-redis 6379)"␍

readme.md

I've started running app services on docker so I don't have to deal with installing shit all the time.

However that means each time you start up a service it comes up on a different random port unless you deliberately map one. But dynamic ports are easier so provided you give the containers for each service a name then they are inspectable using the docker commands.

docker-machine ip default gives you the ip address of the default docker host. docker port name-of-container will list all mapped ports from internal port number to host port number

3306/tcp -> 0.0.0.0:32769

docker inspect --format="{formatstr}" name-of-container will let you pick elements out of the Go formatted data structure

docker inspect --format="{{(index (index .NetworkSettings.Ports \"3306/tcp\") 0).HostPort}}" name-of-mysql

That's a bit unwieldy so I made a docker-service script that will give you the ip, port or ip:port for a container-name and standard port number eg.

$ docker-service odc-mysql 3306 ip
192.168.99.100
$ docker-service odc-mysql 3306 port
32769
$ docker-service odc-mysql 3306 addr
192.168.99.100:32769

dotenv lets you run commands when setting variables by using $(cmd) and all .yml files in rails let you embed ERB so you can use ruby backticks to execute shell commands there and get the output.

database.yml

development: &dev
  host: <%= `docker-service odc-mysql 3306 ip` %>
  port: <%= `docker-service odc-mysql 3306 port` %>

docker-service.sh

#!/bin/bash

set -e

SERVICE=$1
PORT=$2
OUTPUT=${3:-addr}

IP=$(docker-machine ip default)
MAPPED_PORT=$(docker inspect --format="{{(index (index .NetworkSettings.Ports \"${PORT}/tcp\") 0).HostPort}}" ${SERVICE})

case $OUTPUT in
  ip)
    echo "${IP}"
    ;;
  port)
    echo "${MAPPED_PORT}"
    ;;
  *)
    echo "${IP}:${MAPPED_PORT}"
esac