Talkbox

A proof of concept in building browser-based telephony applications using functional programming languages. The back-end is implemented with Elixir, the front-end implemented with Elm.

Why?

• To improve my knowledge of functional programming.
• To learn what types of problems are more/less difficult to solve in the telephony domain using functional languages vs. object oriented languages.
• To gain more experience with event-driven architectures.

What does it do?

• Make a call from the browser
• Receive a call from another browser
• Make a conference call
• Receive a call from a telephone

Design

This project serves as an umbrella enclosing some smaller applications.

Goals

• Small, loosely coupled components, each with a narrow set of responsibilities
• Components that can be tested in isolation

Components

Each of these components is implemented as a child-project under the /apps directory. This was done to promote the abovementioned design goals. Communication between components is achieved by publishing and subscribing to events.

• ContactCentre A Phoenix application that serves the interface allowing the user to make and receive calls. Contains the core business logic for managing calls and conferences.
• Telephony Encapsulates the logic for communicating with the telephony provider. Makes API calls and accepts webhook requests from the telephony provider (also uses Phoenix).
• Events Contains event definitions used to communicate between applications and facilitates publishing of events

Set up

1. Install dependencies

   brew bundle
   mix deps.get
   

2. Install Node packages

   # within the `apps/contact_centre/assets` directory:
   npm install
   

3. Set environment variables

   export TWILIO_ACCOUNT_SID=<account sid>
   export TWILIO_AUTH_TOKEN=<auth token>
   

4. Run the tests

   mix test
   

5. Start the applications

   iex -S mix phx.server
   

6. Open the application

   open http://localhost:5000/?client_name=yourname
   

Docker

To run Talkbox in a container:

1. Ensure Docker is installed and running

2. Compile Elm files

   MIX_ENV=prod mix package_ui
   

3. Build the image

   docker build -t talkbox .
   

4. Ensure the following environment variables are set

   • TWILIO_AUTH_TOKEN
   • TWILIO_ACCOUNT_SID
   • SECRET_KEY_BASE Secret key base for Phoenix
   • COOKIE Erlang cookie
   • TELEPHONY_CLI Must be a verified phone number in Twilio
   • TELEPHONY_WEBHOOK_URL A public url that points to port 4000 on the docker container

5. Run the container

   docker run -p 4000:4000 -p 5000:5000 --env TWILIO_ACCOUNT_SID --env TWILIO_AUTH_TOKEN --env SECRET_KEY_BASE --env TELEPHONY_CLI --env TELEPHONY_WEBHOOK_URL --env COOKIE -it talkbox
   

6. Open the application

   open http://localhost:5000/?client_name=yourname
   

Proposed enhancements

• Resilience to client crash (fetch state from server at load)
• Resilience to server crash (fetch call state from Twilio at boot)
• Rolling deploys (proposing Docker with Consul)