SMS Gatekeeper

A comprehensive SMS rate limiting and monitoring system that validates incoming messages against configurable rate limits. This project demonstrates a microservices architecture with real-time monitoring capabilities.

Project Overview

SMS Gatekeeper is designed to protect SMS infrastructure by enforcing rate limits on both account and phone number levels. The system tracks message history, provides real-time metrics, and offers a user-friendly dashboard for monitoring and analysis.

Architecture

The project follows a microservices architecture with the following components:

Backend (.NET Core)

Located in src/backend/SmsGatekeeper/:

• SmsGatekeeper: The main API service that handles SMS rate limiting logic

  • Validates incoming SMS requests against configurable rate limits
  • Uses Redis for distributed rate limiting with sliding window algorithm
  • Exposes REST endpoints for SMS validation

• SmsDataApi: API service for historical data and metrics

  • Provides endpoints for querying message history with filtering and pagination
  • Hosts SignalR hub for real-time metrics updates

• SmsGatekeeper.Domain: Shared domain models and database context

  • Contains entity models, database context and migrations

• HistoryWorker: Background services

  • Processes and stores SMS events for historical tracking

Frontend (Angular)

Located in src/frontend/:

• Real-time Dashboard: Displays current SMS processing metrics

  • Uses SignalR for real-time updates from the backend
  • Shows current message processing rate

• Message History: Provides searchable history of SMS requests

  • Supports filtering by phone number, account ID, and date range
  • Includes pagination with configurable page size
  • Persists user preferences in localStorage

Technical Features

• Rate Limiting: Implements a sliding window rate limiter using Redis
• Real-time Updates: Uses SignalR for pushing metrics to the frontend
• Responsive UI: Built with Bootstrap
• Fallback Mechanism: Frontend gracefully degrades to mock data if backend is unavailable (for debugging / frontend development purposes)
• Validation: Client and server-side validation for phone numbers (format: 1NPANXXXXX - according to E.164 standard)
• Persistence: Uses SQL Server for historical data and Redis for rate limiting and events / subscriptions.

Development Setup

Backend Requirements

• .NET 8.0 SDK
• SQL Server (or LocalDB)
• Redis

Frontend Requirements

• Node.js (v18+)
• npm

Running the Application

1. Start Redis server

   docker run -p 6379:6379 redis
   

2. Start SQL Server
3. Run the backend services:
4. Run the frontend:

   cd src/frontend
   npm install
   ng serve --open
   

API Endpoints

SmsGatekeeper API

• POST /sms/cansendsms: Validates if a message can be sent based on rate limits

SmsDataApi

• GET /api/history: Retrieves message history with filtering and pagination
• /metrics: SignalR hub for real-time metrics updates

Configuration

Rate limits and other settings can be configured in the respective appsettings.json (or appsettings.{EnvironmentName}.json) files:

• Account-level rate limit
• Phone number rate limit
• Database connection string
• Redis connection string