Khalil Anis Zabat
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Distributed Pub/Sub System

Topic-based Publish/Subscribe Messaging System

A robust, distributed messaging platform built from the ground up that enables efficient communication between applications via a publish/subscribe pattern with advanced topic routing capabilities.

System Architecture

This project implements a complete messaging system with the following components:

  • Message Broker: Central hub managing topic subscriptions and message routing
  • Publisher Client: Applications that send messages to specific topics
  • Subscriber Client: Applications that receive messages from topics they’ve subscribed to
  • Topic Registry: Hierarchical topic management with wildcard support
  • Message Store: Persistent storage for messages with configurable retention

Technical Features

Core Functionality

  • Wildcard Topic Routing: Support for * (single-level) and # (multi-level) wildcards
  • Message Filtering: Server-side filtering based on message properties
  • Format Conversion: Automatic translation between XML, JSON, and custom formats
  • Quality of Service: Configurable delivery guarantees (at-most-once, at-least-once, exactly-once)
  • Persistent Subscriptions: Durable subscriptions surviving client disconnection

Implementation Details

  • Pure Java Implementation: Built from scratch without messaging frameworks
  • Socket Communication: Direct TCP/IP communication for core functionality
  • RabbitMQ Integration: Optional bridge to industry-standard message broker
  • Multithreaded Architecture: Concurrent message processing for high throughput
  • Stream Processing: Efficient handling of message streams

Performance Considerations

The system is designed for high performance in distributed environments:

  • Optimized thread pool for message processing
  • Batched message delivery for efficiency
  • Minimal object creation in hot paths
  • Efficient topic matching algorithms
  • Backpressure handling for slow consumers

Use Cases

This messaging system is suitable for various distributed application scenarios:

  • Event-driven architectures
  • Microservices communication
  • IoT device messaging
  • Real-time data processing
  • System monitoring and logging

The implementation demonstrates deep understanding of messaging patterns, multithreaded programming, and network communication principles.