This document provides instructions for running a Flask Python todo application with a RethinkDB database using Docker containers with links. It explains that containers should only communicate with other containers, not expose ports publicly. It shows commands to run RethinkDB, publishing the admin UI port but keeping other ports internal, and to run the frontend container, linking it to the database container. Environment variables from the linked containers are prefixed and accessible.

1. Links

2. Why?
● Most containers only need to communicate
with other containers
● Only expose the frontend to the public

3. Stack
Todo MVC
Flask python app
Requires rethinkdb
Publish port 5000
RethinkDB
Expose port 27015
Publish port 8080

4. Environment
Links will expose the child container’s exposed
ports, ip, and environment to the parent.
Environment vars are prefixed with the alias of
the child i.e.
DB_PORT_27015_TCP=tcp://xxx.x...:27015

5. Starting Rethinkdb
docker run -d -p 8080 -name rethinkdb -e NAME=todo
crosbymichael/rethinkdb --bind all
Publish the admin ui to the host, keep
everything else internally.
0.0.0.0:49155->8080/tcp, 28015/tcp, 29015/tcp

6. Starting the frontend
docker run -d -p 5000 -link rethinkdb:db -name
todo frontend
#python code using a client lib
proto, ip, port = docker.require_port('db', 28015)
database_name = docker.require_env('db', 'name')

7. Code
github.com/crosbymichael/docker-links-backbone-todo