localityLbPolicy

The load balancing algorithm used within the scope of the locality. The possible values are:

• ROUND_ROBIN: This is a simple policy in which each healthy backend is selected in round robin order.

• LEAST_REQUEST: An O(1) algorithm which selects two random healthy hosts and picks the host which has fewer active requests.

• RING_HASH: The ring/modulo hash load balancer implements consistent hashing to backends. The algorithm has the property that the addition/removal of a host from a set of N hosts only affects 1/N of the requests.

• RANDOM: The load balancer selects a random healthy host.

• ORIGINAL_DESTINATION: Backend host is selected based on the client connection metadata, i.e., connections are opened to the same address as the destination address of the incoming connection before the connection was redirected to the load balancer.

• MAGLEV: used as a drop in replacement for the ring hash load balancer. Maglev is not as stable as ring hash but has faster table lookup build times and host selection times. For more information about Maglev, refer to https://ai.google/research/pubs/pub44824

• WEIGHTED_MAGLEV: Per-instance weighted Load Balancing via health check reported weights. Only applicable to loadBalancingScheme EXTERNAL. If set, the Backend Service must configure a non legacy HTTP-based Health Check, and health check replies are expected to contain non-standard HTTP response header field X-Load-Balancing-Endpoint-Weight to specify the per-instance weights. If set, Load Balancing is weight based on the per-instance weights reported in the last processed health check replies, as long as every instance either reported a valid weight or had UNAVAILABLE_WEIGHT. Otherwise, Load Balancing remains equal-weight.

• WEIGHTED_ROUND_ROBIN: Per-endpoint weighted round-robin Load Balancing using weights computed from Backend reported Custom Metrics. If set, the Backend Service responses are expected to contain non-standard HTTP response header field X-Endpoint-Load-Metrics. The reported metrics to use for computing the weights are specified via the backends[].customMetrics fields. locality_lb_policy is applicable to either:

• A regional backend service with the service_protocol set to HTTP, HTTPS, or HTTP2, and loadBalancingScheme set to INTERNAL_MANAGED.

• A global backend service with the load_balancing_scheme set to INTERNAL_SELF_MANAGED.

• A regional backend service with loadBalancingScheme set to EXTERNAL (External Network Load Balancing). Only MAGLEV and WEIGHTED_MAGLEV values are possible for External Network Load Balancing. The default is MAGLEV. If session_affinity is not NONE, and locality_lb_policy is not set to MAGLEV, WEIGHTED_MAGLEV, or RING_HASH, session affinity settings will not take effect. Only ROUND_ROBIN and RING_HASH are supported when the backend service is referenced by a URL map that is bound to target gRPC proxy that has validate_for_proxyless field set to true. Possible values are: ROUND_ROBIN, LEAST_REQUEST, RING_HASH, RANDOM, ORIGINAL_DESTINATION, MAGLEV, WEIGHTED_MAGLEV, WEIGHTED_ROUND_ROBIN.