How does Envoy perform health checks on service endpoints?

Envoy performs health checks on service endpoints primarily by sending periodic requests to gauge service performance. This mechanism enables Envoy to determine whether a service is healthy and ready to accept traffic. The health check process usually involves sending a specific request to a service endpoint at regular intervals to receive a response. If the endpoint responds appropriately, it indicates that the service is functioning well. Conversely, if the endpoint fails to respond or returns an error, Envoy can mark the service as unhealthy and optionally stop routing traffic to it.

This method of active health checking is crucial for maintaining the reliability and stability of microservices architectures, as it ensures that only services that are operational successfully handle requests. This approach helps maintain the overall health of the application and improves user experience by routing traffic only to functional components of the system. Other methods, such as logging error rates or relying on user feedback, do not provide the real-time and proactive assurance that periodic health checks offer, making them less effective for immediate service health assessments. Traffic redirection strategies, while applicable in certain scenarios, do not inherently assess the health of the service endpoints themselves.