Envoy vs HAProxy: What are the differences?

Introduction

Envoy and HAProxy are popular open-source proxy servers used for load balancing and reverse proxying. While both serve the same purpose, there are several key differences between these two options.

1. Architecture: Envoy follows a decentralized architecture, with each instance capable of full autonomy. This allows for easy scalability and fault tolerance as there is no central point of failure. In contrast, HAProxy follows a centralized architecture, where a single instance acts as the central point for managing traffic distribution.

2. Protocol Support: Envoy supports a wide range of protocols including HTTP, gRPC, WebSocket, TCP, and more. It provides advanced features like HTTP/2 and HTTP/3 support, automatic request splitting, and retries. On the other hand, HAProxy primarily focuses on TCP and HTTP load balancing, with limited support for other protocols.

3. Service Discovery: Envoy has built-in service discovery capabilities that enable automatic detection and load balancing of backend services. It can integrate with service registries like Consul, Kubernetes, and more. While HAProxy supports service discovery through DNS resolution, it lacks the built-in flexibility and advanced features provided by Envoy.

4. Configuration: Envoy uses a dynamic configuration system, where changes can be made without restarting the proxy. It supports dynamic update APIs like xDS (eXtensible Data Discovery Service) for real-time configuration management. In contrast, HAProxy requires manual configuration changes and a restart for updating proxy settings.

5. Observability: Envoy offers extensive observability via built-in metrics, logging, and tracing capabilities. It provides detailed statistics about traffic, latency, error rates, and more. HAProxy also provides basic logging and monitoring features but lacks the comprehensive observability features offered by Envoy.

6. Community and Adoption: Envoy has gained significant traction in recent years, backed by a vibrant community and strong industry support. It is heavily used in cutting-edge environments like Istio service mesh and Kubernetes ingress. HAProxy, while also popular, has been around for a longer time and has a more established user base.

In summary, Envoy and HAProxy differ in their architecture, protocol support, service discovery capabilities, configuration management, observability features, and community adoption. Envoy offers a more decentralized and feature-rich solution, while HAProxy is a more traditional load balancing option with a longer history.