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README.md

Home Broker: NestJS Microservice

This API works as an intermediate between client, Kafka and another Go Microservice. Inside this API you'll have persisting and part of the business logic regarding a home broker.

📖 Table of Contents

📝 Requirements

💡 Features

With this API you'll be able to:

  • Manage Assets, Wallets and Orders in a home broker;
  • Listen to negotiated trades sent via Kafka by GO Service;
  • Get data using Server Sent Events (SSE) in order to get real time changes regarding daily changes in Assets, Orders or Wallets;
  • Listen to changes in MongoDB and send it to client using SSE, the SSE endpoint send a payload to the client in the subscribed endpoint.

📦 Docs: Architecture, Endpoints, Kafka topics and more

This API has different types of resources and ways to communicate with client and another services (such as Kafka topics), beyond that, a MongoDB database is used to store home broker data.

Architecture

Nest Architecture

REST Endpoints

Base URL: http://localhost:3000

Create a financial asset to be negotiated

POST /assets

REQUEST BODY:

{
  "id": "asset1",
  "symbol": "A1",
  "price": 100
}

RESPONSE BODY:

{
  "id": "asset1",
  "symbol": "A1",
  "price": 100,
  "created_at": "2023-07-14T01:19:36.015Z",
  "updated_at": "2023-07-14T01:19:36.015Z"
}

List all assets to be negotiated

GET /assets

RESPONSE BODY:

[
  {
    "id": "asset1",
    "symbol": "asset1",
    "price": 199,
    "created_at": "2023-07-12T23:26:13.224Z",
    "updated_at": "2023-07-12T23:29:32.951Z"
  }
]

Create a wallet

POST /wallets

REQUEST BODY:

{
  "id": "wallet1"
}

RESPONSE BODY:

{
  "id": "wallet3",
  "created_at": "2023-07-14T01:51:42.950Z",
  "updated_at": "2023-07-14T01:51:42.950Z"
}

List all wallets

GET /wallets

RESPONSE BODY:

[
  {
    "id": "wallet1",
    "created_at": "2023-07-12T23:26:13.241Z",
    "updated_at": "2023-07-12T23:26:13.241Z"
  }
]

Add asset to wallet

POST /wallets/:wallet_id/assets

REQUEST BODY:

{
  "asset_id": "asset1",
  "shares": 10
}

RESPONSE BODY:

{
  "id": "64b0ab6ed743e0f15b94ba5a",
  "wallet_id": "wallet1",
  "asset_id": "asset1",
  "shares": 10,
  "version": 1,
  "created_at": "2023-07-14T01:57:02.199Z",
  "updated_at": "2023-07-14T01:57:02.199Z"
}

List wallets with its assets

GET /wallets/:wallet_id/assets

RESPONSE BODY:

[
  {
    "id": "64af3695361708b34d0d12c6",
    "wallet_id": "wallet1",
    "asset_id": "asset1",
    "shares": -89000,
    "version": 100,
    "created_at": "2023-07-12T23:26:13.257Z",
    "updated_at": "2023-07-12T23:29:32.915Z",
    "Asset": {
      "id": "asset1",
      "symbol": "asset1",
      "price": 199
    }
  }
]

Init order transaction

POST /wallets/:wallet_id/orders

REQUEST BODY:

{
  "asset_id": "asset1",
  "shares": 5,
  "price": 100,
  "type": "SELL"
}

RESPONSE BODY:

{
  "id": "64b0ae2ed743e0f15b94ba5b",
  "wallet_id": "wallet1",
  "asset_id": "asset1",
  "shares": 5,
  "price": 100,
  "type": "SELL",
  "status": "PENDING",
  "partial": 5,
  "version": 1,
  "created_at": "2023-07-14T02:08:46.641Z",
  "updated_at": "2023-07-14T02:08:46.641Z"
}

List all order transactions

GET /wallets/:wallet_id/orders

RESPONSE BODY:

[
  {
    "id": "64b0ae2ed743e0f15b94ba5b",
    "wallet_id": "wallet1",
    "asset_id": "asset1",
    "shares": 5,
    "price": 100,
    "type": "SELL",
    "status": "PENDING",
    "partial": 5,
    "version": 1,
    "created_at": "2023-07-14T02:08:46.641Z",
    "updated_at": "2023-07-14T02:08:46.641Z",
    "Transactions": [],
    "Asset": {
      "id": "asset1",
      "symbol": "asset1"
    }
  }
]

SSE Routes

Triggered when daily asset is created in MongoDB

GET|SSE /assets/:id/daily/events

RESPONSE BODY:

{
  "type": "asset-daily-created",
  "data": {
    "id": "64af369dd743e0f15b94b769",
    "asset_id": "asset2",
    "price": 205,
    "date": "2023-07-12T23:26:21.654Z",
    "created_at": "2023-07-12T23:26:21.656Z",
    "updated_at": "2023-07-12T23:26:21.656Z"
  }
}

Triggered when asset price is updated in MongoDB

GET|SSE /assets/events

RESPONSE BODY:

{
  "type": "asset-price-changed",
  "data": {
    "id": "asset3",
    "symbol": "A1",
    "price": 100,
    "created_at": "2023-07-14T01:19:36.015Z",
    "updated_at": "2023-07-14T01:19:36.015Z"
  }
}

Triggered when an order is updated or created in MongoDB

GET|SSE /wallets/:wallet_id/orders/events

RESPONSE BODY 1:

{
  "type": "order-created",
  "data": {
    "id": "64af369d361708b34d0d12dd",
    "wallet_id": "wallet2",
    "asset_id": "asset2",
    "shares": 1000,
    "price": 215,
    "type": "BUY",
    "status": "CLOSED",
    "partial": 0,
    "version": 2,
    "created_at": "2023-07-12T23:26:21.505Z",
    "updated_at": "2023-07-12T23:26:21.629Z"
  }
}

RESPONSE BODY 2:

{
  "type": "order-updated",
  "data": {
    "id": "64af369d361708b34d0d12dd",
    "wallet_id": "wallet2",
    "asset_id": "asset2",
    "shares": 1000,
    "price": 215,
    "type": "BUY",
    "status": "CLOSED",
    "partial": 0,
    "version": 2,
    "created_at": "2023-07-12T23:26:21.505Z",
    "updated_at": "2023-07-12T23:26:21.629Z"
  }
}

Triggered when an asset belonging to a wallet is updated

GET|SSE /wallets/:wallet_id/assets/events

RESPONSE BODY:

{
  "type": "wallet-asset-updated",
  "data": {
    "_id": "64b0ab6ed743e0f15b94ba5a",
    "wallet_id": "wallet1",
    "asset_id": "asset1",
    "shares": 10,
    "version": 1,
    "created_at": "2023-07-14T01:57:02.199Z",
    "updated_at": "2023-07-14T01:57:02.199Z"
  }
}

Kafka Topics

You can make a negotiation in home broker through a Kafka topic in order to buy or sell assets. You'll see below the routes whose send and receive data from Kafka.

Execute transaction consumer

Receive from topic: output

Route: /wallets/:wallet_id/orders/output

BODY FROM TOPIC:

{
  "order_id": "64af370d361708b34d0d13b9",
  "investor_id": "wallet2",
  "assset_id": "asset2",
  "order_type": "BUY",
  "status": "CLOSED",
  "partial": 0,
  "shares": 1000,
  "transactions": [
    {
      "transaction_id": "fb712cef-9217-4369-b49b-b172bc50f150",
      "buyer_id": "64af370d361708b34d0d13b9",
      "seller_id": "64af370d361708b34d0d13b8",
      "asset_id": "asset2",
      "price": 260,
      "shares": 1000
    }
  ]
}

Init transaction

Send to topic: input

POST Route: /wallets/:wallet_id/orders/output

BODY TO TOPIC:

{
  "order_id": "64af36a7361708b34d0d12f1",
  "investor_id": "wallet2",
  "asset_id": "asset2",
  "shares": 1000,
  "price": 220,
  "order_type": "BUY"
}

MongoDB (Prisma Schema)

Mongo Diagram

MongoDB Events (with SSE)

Event When is Triggered? SSE Route to be Called
asset-daily-created When a new asset is created /assets/:id/daily/events
asset-price-changed When an asset has its price changes during a negotiation /assets/events
order-created When a negotiation begins /wallets/:wallet_id/orders/events
order-updated When a negotiation is updated /wallets/:wallet_id/orders/events
wallet-asset-updated When an asset that belongs to an asset changes /wallets/:wallet_id/assets/events

🚀 How to Run?

The steps below will show you how to use this service properly:

  1. You need to start GO Service;
  2. Start this service with command:
docker-compose up
  1. Optional, but not mandatory, you may subscribe to SSE endpoints, and in your command line, access the API with docker-compose and run the command script as shown below:
docker-compose exec app bash
npm run command simulate-assets-price

This command simulate the message broker working, this creates wallets, assets, negotiations, etc... Click here to see the implementation of this command;

  1. Optional also, you may want to use the REST Extension in VSCode.

🔄 How to use this?

You can simulate the home broker working by running:

npm run command simulate-assets-price

This command will execute all process and endpoints inside the home broker, also will trigger the SSE routes as shown above in the Docs.

⚙️ Made With:

  • NestJS 10.0.0
  • Prisma 4.16.1
  • MongoDB 5.0.17
  • NodeJS 20.0.0
  • Typescript 5.1.3
  • Docker 20.10.7

🧑🏻‍💻 Author

Matheus Oliveira da Silva - Github | Linkedin