Exclusible Project

This project is a simple microservice architecture with two services(exchange rate and user api). The services communicate through a message broker like Redis PubSub.

High-level Architecure

Problem

When building software solutions, it's good to understand the underlying problem. This understanding enable us to build resilient and effective applications that are easy to use, maintain and scale.

For this technical task, I see a problem with administrators of a system finding it difficult to update rates and let user be aware of these changes in realtime. I also see an existing pattern of updating rates on a system that needs to be better.

Solution

For a task like, I'm tasked with the responsibility to provide a solution. And here are a few steps I'm taking.

Service that stream live rates from CoinmarketCap or Kraken Exchange
A service that shares these rates with another services where users' information are stored
A service that gets notified of new rates
A service that provides an endpoint for admin to add spread to exchange rate
Websocket with subscription for Exchange rate on the FE (connecting to external API or websocket)

These solutions are my assumptions and not what may seem!!

Technologies

For every problem given to an engineer, there will be tools needed to help them solve those problems. Here are the technologies used for this task.

JavaScript (Language)
Node.js (Run-time)
MySQL (Datastore)
Typescript (Typing)
Redis (Caching & PubSub)
Adonisjs (Framework)
Jest (Testing)
Japa (Testing)
Docker (Virtualization, Contanerization, Orchestration)
Socket.io (Websocket)

The Services

As earlier mentioned and seen on the high-level architecture above, we need two services, and they should be able to communicate effectively with each other. Here are the services:

Exchange Rate
- This service is responsible for getting rates from Kraken exchange via a websocket connection
- Publishing the rates to Redis
- Providing an endpoint to get rates via http
User Api
- The service enable users to register, login and logout
- It's responsible for getting rates published by the exchange rate service through subscription
- It stores spread values on a DB table
- It provides an endpoint an Admin user to update rates
- It creates Websocket connection for the Frontend to stream live rates from
- It broadcasts live rates to the frontend
- It provides an endpoint for the frontend to get rates + spread via with http

How to use

Running Services

The two services and other depencies like MySQL and Redis, are all bundled into a docker container. This means, we only need Docker on a machine to run the services.
1. You can run the services by executing the docker command below:
```
  docker compose up
```
As soon as the container is running, you may run the command below to ssh into the services
```
  # Exchange rate
  docker exec -it exchange-rate-service sh 
  
  # User Api
  docker exec -it user-api-service sh
```
You need to ssh into the services to be able to run migrations and seeders. Here are the commands:
```
  node ace migration:

  # To Seed data on User Api, run this command
  node ace db:seed
```
API Documentation

The documentation for all API endpoints are found on the link below: https://documenter.getpostman.com/view/6955209/2s8YY9vmW9
Collection

Find link to the postman collection for all endpoints below:

Exclusible Postman Collection

Websocket

The websocket server is accessible on the link below:

ws://127.0.0.1:3334

As soon as the user-api-service is running, you can make websocket connection the link above.

Websocket payload

{
   BTC_USD: {
      original: { buy: 20249, sell: 20249 },
      withSpread: { buy: 20699, sell: 20682 },
      currentSpread: { buy: 450, sell: 433 }
   }
}

Websocket event

All rates are broadcasted through the rates:live event.

Misc

I created a frontend page to demo rate streaming. You may access the page by visiting the link below. Do not forget to check out to the ws-client-test branch.

http://127.0.0.1:3334/ws-test/

# Ensure you switch branch to "ws-client-test"

coderatio/exclusible