haproxy-load-balancing-simulation

A comprehensive load balancing simulation project built with Java, HAProxy, and Docker Compose. This project demonstrates HTTP and TCP load balancing, health checks, and advanced failover behaviors using multiple backend services and a backup server. You can easily observe how HAProxy distributes traffic, handles server failures, and automatically routes requests to backup infrastructure, all within an isolated container environment.

Key Features:

• Supports both Layer 4 (TCP) and Layer 7 (HTTP) load balancing with separate HAProxy configurations
• Path-based routing and per-endpoint failover logic for HTTP requests (Layer 7)
• Transparent round robin balancing and failover for generic TCP traffic (Layer 4)
• Automatic backup server activation in case of backend failures

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How to Build and Run:

docker compose up --build

All components will be built and started automatically. This includes:

• Three main Java backend servers and a dedicated backup server
• HAProxy in both Layer 4 (TCP) and Layer 7 (HTTP) proxy modes
• Pre-configured routing and health check scenarios

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How to Simulate Failover and Load Balancing:

• Test HTTP Layer 7: Send requests to http://localhost:8087/ with different endpoints (e.g., /api/hello, /auth/hello, /other/hello, /) Observe how traffic is routed according to endpoint and how backup takes over if a primary server fails.

• Test TCP Layer 4: Send requests to http://localhost:8084/ and see round robin balancing among healthy servers. When all primary servers are down, backup-server automatically handles all traffic.

• Simulate Failover: While the system is running, stop any backend server using:

  docker stop server2

  or

  docker stop server1

  Watch as HAProxy reroutes traffic to the remaining healthy servers or backup according to your configuration.

• Logs and Troubleshooting: All HAProxy and backend logs can be viewed using:

  docker logs <container_name>

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