Load Balancing

For HTTP, HTTP/2, and gRPC connections, Linkerd automatically load balances requests across all destination endpoints without any configuration required. (For TCP connections, Linkerd will balance connections.)

Linkerd uses an algorithm called EWMA, or exponentially weighted moving average, to automatically send requests to the fastest endpoints. This load balancing can improve end-to-end latencies.

Service discovery

For destinations that are not in Kubernetes, Linkerd will balance across endpoints provided by DNS.

For destinations that are in Kubernetes, Linkerd will look up the IP address in the Kubernetes API. If the IP address corresponds to a Service, Linkerd will load balance across the endpoints of that Service and apply any policy from that Service’s Service Profile. On the other hand, if the IP address corresponds to a Pod, Linkerd will not perform any load balancing or apply any Service Profiles.

Note

If working with headless services, endpoints of the service cannot be retrieved. Therefore, Linkerd will not perform load balancing and instead route only to the target IP address.

Load balancing gRPC

Linkerd’s load balancing is particularly useful for gRPC (or HTTP/2) services in Kubernetes, for which Kubernetes’s default load balancing is not effective.