Java Multi-Threaded TCP Load Balancer

A Layer 4 (Transport Layer) Load Balancer built from scratch using Java's native Networking API. This project acts as a Reverse Proxy that distributes incoming traffic across multiple backend servers using various balancing algorithms.

Features

• TCP Socket Streaming: High-performance byte-level proxying between clients and backends.
• Multi-threaded Architecture: Utilizes a ThreadPool to handle multiple concurrent connections efficiently.
• Strategy Design Pattern: Decoupled balancing logic allowing easy switching between algorithms.
• HTTP/1.1 Compatible: Includes connection handling (Connection: close) to prevent hanging proxy streams.

System Architecture

The system follows a clean, modular structure:

1. Core: Manages the ServerSocket and delegates connection handling to workers.
2. Strategy: The "Brain" of the system. Implements the balancing logic.
3. Backend: Mock HTTP servers to demonstrate the traffic distribution.

Balancing Strategies

• Round Robin: Distributes requests in a circular, fair order (1, 2, 1, 2...).
• Random: Uses probabilistic distribution to select the next available backend.

Getting Started

Prerequisites

• JDK 17 or higher.

Compilation

From the src directory, run:

javac br/com/luisfelipe/loadbalancer/Main.java br/com/luisfelipe/loadbalancer/core/*.java br/com/luisfelipe/loadbalancer/backend/*.java br/com/luisfelipe/loadbalancer/strategy/*.java

Running the project

java br.com.luisfelipe.loadbalancer.Main

The Load Balancer will start on port 8080, proxying to backends on ports 8081 and 8082.