The challenge:

You need to build a little event/stream-powered chat backend.

Here is the expected flow in a nutshell:

• Messages flow through a Kafka broker, you capture these messages and
  • ... place them in permanent storage
  • ... as well as deliver them to a redis pubsub
• Write a websocket server that accepts subscribe events and:
  • ... returns the last N messages from permanent storage
  • ... and returns messages in real time from redis pubsub from the corresponding channel

You are free to structure the projects, choose frameworks and/or libraries as you see fit to deliver on this project. Also feel free to use any of the databases provided in the docker-compose file or add your own choice to it.

Visual guideline

Here's a little example flow in case you need a little push to get going:

WSServer flow:

sequenceDiagram
WSClient ->> WSServer: { command: 'subscribe', channel: '#kerno-challenge' }
WSServer -->> Database: getMessages(channel)
WSServer -->> PubSub: subscribe(channel)
WSServer -->> WSServer: 
WSServer ->> WSClient: [messages]

Loading

StreamWorker flow:

sequenceDiagram
Worker ->> Kafka: subscribe(channel)
Kafka -->> Worker: [messages]
Worker -->> Database: insert(channel, message)
Worker -->> PubSub: publish(channel, message)

Loading