This is a simple chat application using Elixir/Phoenix and WebSockets. The purpose is to explore Event Sourcing; all events are first written to a Kafka log which are then propagated to a PostgreSQL database for reading.
This design was inspired by Martin Kleppman's talk "Turning the database inside out with Apache Samza".
Installing Kafka:
$ brew install kafka
$ brew services start zookeeper
$ brew services start kafka
Zookeeper is running on port 2181, Kafka on port 9092.
To start your Phoenix app:
- Install dependencies with
mix deps.get - Create and migrate your database with
mix ecto.create && mix ecto.migrate - Install Node.js dependencies with
npm install - Start Phoenix endpoint with
mix phoenix.server
Now you can visit localhost:4000 from your browser.
There is a separate process that streams messages from Kafka and writes them to Postgres.
$ mix run lib/ingest/writer.exs
Not sure what the best way to run this is in the context of an Elixir/OTP application.