🏗️ Jakarta EE Learning + Golang LoadBalancer

A distributed system project demonstrating a high-performance Golang Load Balancer sitting in front of a Java (JSP/Servlet) Backend.

🌌 System Architecture

This project bridges modern systems programming (Go) with enterprise web standards (Java Jakarta EE).

📊 Full-Stack Architecture Flow:

graph TD
    User((User/Browser)) -->|Port 8080| LB[Go Load Balancer]
    
    subgraph "Infrastructure Layer (Go)"
        LB -->|Round Robin| RR[Routing Logic]
        RR -.->|Heartbeat| HC{Health Check}
    end

    subgraph "Backend Tier"
        RR -->|Forward| J[Java Backend: Tomcat/Glassfish]
        RR -->|Forward| G[Go Backend: Native]
        
        subgraph "Data Persistence"
            J -->|JDBC| DB[(H2 Database)]
        end
    end

    style LB fill:#00ADD8,stroke:#333,stroke-width:2px,color:#fff
    style J fill:#f89820,stroke:#333,stroke-width:2px,color:#fff
    style DB fill:#4479A1,stroke:#333,stroke-width:1px,color:#fff
    style G fill:#00ADD8,stroke:#333,stroke-width:2px,color:#fff

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• The Front Door: Go Load Balancer (Port 8080) - Go Logic Details
• Backend Instance 1: Java JSP/Servlet on Tomcat (Port 8081) - Java Logic Details
• Backend Instance 2: Go Native Microservice (Port 8082) - Serving as a fallback/secondary node.

📂 Explore the Codebase

• Java Backend (Jakarta EE/Tomcat) — View the core business logic and JSP templates.
• Go Infrastructure (Load Balancer) — View the networking logic, health checks, and goroutines.

🛠️ Key Infra Features

1. Dynamic Rerouting: If the Java Tomcat server is killed, the Load Balancer detects the failure within 5 seconds and automatically reroutes all traffic to the Go backend.
2. Cross-Language Proxying: Demonstrates the ability to manage traffic between different language runtimes (JVM and Go Binary).
3. Concurrency Control: Utilizes Go's concurrency primitives to handle health checks without blocking incoming user requests.

🛠️ Prerequisites & Setup

This system is designed to be cross-platform. Ensure you have the following based on your OS:

1. Infrastructure Layer (Go)

• Go 1.26+:
  • macOS: brew install go
  • Windows: Download the .msi from golang.org
  • Linux (Ubuntu/Debian): sudo apt install golang-go

2. Backend Layer (Java)

• OpenJDK 21+:
  • macOS/Linux: Use sdk install java 21-open (via SDKMAN!)
  • Windows: Download from Adoptium (Eclipse Temurin)
• Apache Tomcat 11: Required for Jakarta EE 11 support.
• Maven: To build the .war file for the Java backend.

3. Containerization (Optional but Recommended)

• Docker Desktop (Mac/Windows) or Docker Engine (Linux) to run the entire stack via one command.

🛠️ Developer's Notes & "Real-World" Considerations

While this project is a fully functional distributed system, it was built as a deep-dive into Infrastructure Logic and Cross-Runtime Communication. Here is how this would differ in a modern production environment:

• The "JSP" Reality: I chose JSP/Servlets to understand the fundamental request-response lifecycle of the Java ecosystem. In a modern 2026 production environment, I would replace this with a Spring Boot/Quarkus REST API and a decoupled frontend (React/Next.js).
• Database Scaling: This system uses an H2 In-Memory Database for zero-config portability. For a production CRUD application, a persistent RDBMS like PostgreSQL or MySQL would be used, likely managed via an ORM like Hibernate or Go's GORM.
• Load Balancing: The Go Load Balancer here is a "from-scratch" implementation of a Round Robin algorithm. In enterprise-grade infra, one might use Nginx, HAProxy, or AWS ELB, but building it in Go proves an understanding of how those tools work under the hood.
• Security: This project prioritizes architectural clarity over security hardening. Production apps would require JWT/OAuth2 for auth and TLS/SSL for all container-to-container traffic.