“What I cannot create. I do not understand.” ― Richard Feynman
This project implements a high-performance Layer 4 load balancer using modern C++. The architecture is inspired by NGINX and Envoy proxy, designed to efficiently handle high volumes of network traffic at the transport layer (TCP/UDP). The load balancer uses a process-per-core model and leverages io_uring for event-driven I/O management, ensuring low latency and scalable performance.
- IO_uring: High-performance I/O operations using io_uring
- Modern C++: Written in C++17
- Process-per-Core: The load balancer spawns a dedicated process for each CPU core, ensuring maximum parallelism and efficient use of system resources.
- Event Loop with io_uring: The core of the load balancer revolves around an io_uring-based event loop. This allows the system to efficiently handle I/O operations (e.g., network connections, file descriptors) with minimal system calls and context switches.
- Layer 4 Protocol Handling: Focuses on balancing traffic at the transport layer. Currently supports TCP and UDP traffic, with plans to extend protocol support.
- Worker Processes: Each CPU core runs a separate worker process, similar to how NGINX operates. This provides better resource utilization and scales well with multi-core systems.
- Event-Driven Design: The event loop uses io_uring to queue and manage I/O operations asynchronously, significantly reducing the overhead of traditional I/O mechanisms like
epoll
orselect
. - Connection Handling: Each worker process independently manages client connections and handles incoming traffic. The load balancer distributes incoming requests across available backends based on predefined algorithms (e.g., round-robin, least-connections).
The architecture of this Layer 4 load balancer takes inspiration from the efficient design principles of NGINX. A key feature of NGINX's architecture is its worker model, which is designed to handle thousands of connections per worker with minimal resource overhead.
The load balancer does not spawn a new process or thread for every incoming connection in this model. Instead, a shared listening socket is used by all workers to accept new requests. Each worker then runs a highly efficient run-loop, which manages the processing of multiple connections simultaneously within a single process. This approach eliminates the need for explicit connection distribution, as the OS kernel handles the allocation of connections to available workers.
Upon startup, a set of listening sockets is created, and each worker process continuously handles the lifecycle of a connection, including accepting, reading, processing, and writing responses. The model is designed to be asynchronous and non-blocking as much as possible, using modular event notifications and callback functions to handle tasks like I/O operations and connection management.
Non-blocking Event Loop The core of this architecture is an event loop that uses io_uring for high-performance I/O operations. Like NGINX, the goal is to avoid blocking operations. Workers are designed to remain highly responsive, waiting for network or I/O events to occur before processing them. The event loop processes tasks asynchronously, leveraging callbacks and fine-tuned timers to handle tasks efficiently without stalling.
- L7 htto Load Balancing: Extend the load balancer to support Layer 7 (HTTP) load balancing, including features like URL-based routing, header-based routing, and SSL termination.
- Dynamic Configuration: Support dynamic configuration updates without requiring a restart of the load balancer.
- Monitoring: Integrate monitoring capabilities to track performance metrics and diagnose issues.
- Traffic Routing for A/B Testing: Implement a feature to route a certain percentage of traffic to a new version of the service for A/B testing or canary deployments.
MIT