# 📢 Distributed Notification and Alert System

## 📌 Overview

This project is a **distributed backend system** designed to process and deliver notifications across multiple channels (Email, SMS, Push). It supports **real-time alerts, scheduled notifications, user preference handling, and query-driven delivery logic**. The system is built for scalability, resilience, and extensibility, leveraging **Node.js, Kafka, MongoDB, and Dockerized microservices**.

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## 🎯 Key Features

- **Real‑Time & Scheduled Delivery**: Immediate processing for urgent alerts, scheduled pipelines for deferred notifications.
- **User Preferences**: Configurable quiet hours, channel selection, and throttling limits.
- **Advanced Query Logic**:
  - [Throttling](ca://s?q=Notification_throttling) to enforce per‑user limits.
  - [Quiet Hours Filtering](ca://s?q=Quiet_hours_notification_filtering).
  - [Deduplication](ca://s?q=Notification_deduplication) of similar alerts.
  - [Aggregation](ca://s?q=Notification_aggregation) of low‑priority notifications.
  - [Priority‑Based Delivery](ca://s?q=Priority_based_notification_delivery).
- **Resilient Messaging**: Kafka decouples ingestion, processing, and delivery for fault tolerance.
- **Retry & Logging**: Failed deliveries retried with logging into MongoDB.
- **Analytics API**: `/analytics` endpoint for delivery stats, retries, and engagement metrics.

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## 🎯 Objectives

- Ingest and validate notification requests via APIs.
- Process notifications in real-time or schedule them for future delivery.
- Respect **user preferences** (quiet hours, channel selection, throttling limits).
- Support **deduplication, aggregation, and prioritization** of alerts.
- Deliver notifications reliably with retry logic and logging.
- Provide analytics and monitoring endpoints for system visibility.

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## ⚙️ Implementation Details

- **Backend Framework**: Node.js, Express.js
- **Messaging System**: Apache Kafka
- **Database**: MongoDB (notifications, preferences, analytics)
- **Job Scheduling**: node-schedule
- **ORM**: Mongoose
- **Containerization**: Docker + Docker Compose

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## 🏗️ System Components

1. **Notification Ingestion & Validation Service**
   - `/notify` API endpoint to receive requests.
   - Validates payload and publishes to Kafka topic `notifications`.

2. **Notification Processing & Scheduling Engine**
   - Real-time delivery for urgent/high-priority alerts.
   - Scheduled notifications stored in MongoDB and checked periodically.

3. **User Preferences & Rules**
   - Preferred channels (Email, SMS, Push).
   - Quiet hours (Do Not Disturb).
   - Notification limits (e.g., max 3/hour).

4. **Query Logic**
   - **Throttling**: Restrict notifications per user-defined limits.
   - **Quiet Hours Filtering**: Reschedule notifications outside quiet hours.
   - **Deduplication**: Suppress duplicate alerts within a time window.
   - **Aggregation**: Batch low-priority notifications into summaries.
   - **Urgent Alerts**: Immediate bypass of scheduling.

5. **Notification Delivery Service**
   - Channels: Email, SMS, Push (mock integrations).
   - Retry mechanism for failed deliveries.
   - Logging of statuses in MongoDB.

6. **Analytics & Monitoring**
   - `/analytics` endpoint for delivery stats, retries, and engagement metrics.

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## 🛠️ Installation & Setup

```bash
# Clone the repository
git clone https://github.com/akshay931/distri_notification_and_alert_system.git
cd distri_notification_and_alert_system

# Install dependencies
npm install

# Start services with Docker Compose
docker-compose up -d
```