What is the distinction between a cluster and an endpoint in Envoy?

In Envoy, a cluster comprises multiple endpoints, which represent individual service instances. This means that a cluster is a logical grouping that can include multiple instances of a service, each of which is identified as an endpoint. The cluster serves as a load balancing unit, directing incoming requests to one of the available endpoints based on the load balancing strategy defined in Envoy’s configuration.

The distinction is significant because it reflects the architecture of microservices, where a single service might be deployed in multiple instances to handle varying levels of traffic and provide redundancy. Each endpoint is a specific instance of the service that can be addressed directly, while the cluster is used to manage these instances collectively for routing traffic efficiently.

Understanding this relationship is crucial for configuring Envoy properly to ensure that traffic is distributed among the available service instances and that the system remains resilient.