After the frontend and the backend of the load balancer are defined, traffic is evenly distributed among endpoints in the backend. But what if one of the endpoints is unavailable? In that case, some of the requests will fail until we detect the issue or even fail indefinitely, in case issue is not detected. The load balancer would send a request to all the defined endpoints in the backend pool and the request would fail when directed to an unavailable server.
This is why we introduce the next two components in the load balancer—health probes and rules. These components are used to detect issues and describe what to do when issues are detected.
Health probes constantly monitor all endpoints defined in the backend pool and detect whether any of them become unavailable.
