The document discusses linking Docker containers together for a Todo application using Flask, RethinkDB, and Docker links. It explains that containers only need to communicate with each other, not publicly. It provides instructions for starting RethinkDB with port bindings and environment variables, then starting the Flask frontend container linked to RethinkDB to access the database.

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