Balance Service Library

A lightweight NestJS library that pushes balance update messages into a RabbitMQ queue named BALANCE and consumes them to update Redis keys in the form userId:balance:{INR:10,USD:20}.

Features

• Class-based BalanceService with small, focused methods
• Uses amqplib for RabbitMQ and ioredis for Redis
• Easy to import as a linked package (npm link or local path)

Getting Started

1. Install dependencies:

   npm install

2. Build the library:

   npm run build

3. In your NestJS application, add the library as a dependency. If you're developing locally, you can use npm link or a relative path in package.json:

   "dependencies": {
     "balance-service-lib": "file:../az-omi-balance"
   }

4. Import the module and inject the service:

   import { Module } from '@nestjs/common';
   import { BalanceModule, BalanceService } from 'balance-service-lib';
   
   @Module({
     imports: [BalanceModule],
     providers: [],
   })
   export class AppModule {
     constructor(private readonly balance: BalanceService) {
       // ensure service is initialized by Nest
     }
   }

5. Use the service to push messages:

   this.balance.pushToQueue('1234', 'INR', -10);

The consumer automatically starts on module initialization and persists balance data to Redis.

Configuration

• RABBIT_URL – URL to RabbitMQ server (default: amqp://localhost)
• REDIS_URL – URL to Redis server (default: redis://localhost:6379/0)