grpc-js-xds: Add wrr_locality to LB policy registry

packages/grpc-js-xds/package.json

@@ -12,7 +12,7 @@
     "prepare": "npm run generate-types && npm run generate-interop-types && npm run generate-test-types && npm run compile",
     "pretest": "npm run compile",
     "posttest": "npm run check",
-    "generate-types": "proto-loader-gen-types --keepCase --longs String --enums String --defaults --oneofs --includeComments --includeDirs deps/envoy-api/ deps/xds/ deps/googleapis/ deps/protoc-gen-validate/ -O src/generated/ --grpcLib @grpc/grpc-js envoy/service/discovery/v3/ads.proto envoy/service/load_stats/v3/lrs.proto envoy/config/listener/v3/listener.proto envoy/config/route/v3/route.proto envoy/config/cluster/v3/cluster.proto envoy/config/endpoint/v3/endpoint.proto envoy/extensions/filters/network/http_connection_manager/v3/http_connection_manager.proto udpa/type/v1/typed_struct.proto xds/type/v3/typed_struct.proto envoy/extensions/filters/http/fault/v3/fault.proto envoy/service/status/v3/csds.proto envoy/extensions/load_balancing_policies/wrr_locality/v3/wrr_locality.proto envoy/extensions/load_balancing_policies/ring_hash/v3/ring_hash.proto envoy/extensions/load_balancing_policies/pick_first/v3/pick_first.proto envoy/extensions/clusters/aggregate/v3/cluster.proto envoy/extensions/transport_sockets/tls/v3/tls.proto envoy/config/rbac/v3/rbac.proto envoy/extensions/filters/http/rbac/v3/rbac.proto envoy/extensions/load_balancing_policies/client_side_weighted_round_robin/v3/client_side_weighted_round_robin.proto",
+    "generate-types": "proto-loader-gen-types --keepCase --longs String --enums String --defaults --oneofs --includeComments --includeDirs deps/envoy-api/ deps/xds/ deps/googleapis/ deps/protoc-gen-validate/ -O src/generated/ --grpcLib @grpc/grpc-js envoy/service/discovery/v3/ads.proto envoy/service/load_stats/v3/lrs.proto envoy/config/listener/v3/listener.proto envoy/config/route/v3/route.proto envoy/config/cluster/v3/cluster.proto envoy/config/endpoint/v3/endpoint.proto envoy/extensions/filters/network/http_connection_manager/v3/http_connection_manager.proto udpa/type/v1/typed_struct.proto xds/type/v3/typed_struct.proto envoy/extensions/filters/http/fault/v3/fault.proto envoy/service/status/v3/csds.proto envoy/extensions/load_balancing_policies/wrr_locality/v3/wrr_locality.proto envoy/extensions/load_balancing_policies/ring_hash/v3/ring_hash.proto envoy/extensions/load_balancing_policies/pick_first/v3/pick_first.proto envoy/extensions/clusters/aggregate/v3/cluster.proto envoy/extensions/transport_sockets/tls/v3/tls.proto envoy/config/rbac/v3/rbac.proto envoy/extensions/filters/http/rbac/v3/rbac.proto envoy/extensions/load_balancing_policies/client_side_weighted_round_robin/v3/client_side_weighted_round_robin.proto envoy/extensions/load_balancing_policies/wrr_locality/v3/wrr_locality.proto",
     "generate-interop-types": "proto-loader-gen-types --keep-case --longs String --enums String --defaults --oneofs --json --includeComments --includeDirs proto/ -O interop/generated --grpcLib @grpc/grpc-js grpc/testing/test.proto",
     "generate-test-types": "proto-loader-gen-types --keep-case --longs String --enums String --defaults --oneofs --json --includeComments --includeDirs proto/ -O test/generated --grpcLib @grpc/grpc-js grpc/testing/echo.proto"
   },

packages/grpc-js-xds/src/index.ts

@@ -31,6 +31,7 @@ import * as round_robin_lb from './lb-policy-registry/round-robin';
 import * as typed_struct_lb from './lb-policy-registry/typed-struct';
 import * as pick_first_lb from './lb-policy-registry/pick-first';
 import * as weighted_round_robin_lb from './lb-policy-registry/weighted-round-robin';
+import * as wrr_locality from './lb-policy-registry/wrr-locality';
 
 export { XdsServer } from './server';
 export { XdsChannelCredentials, XdsServerCredentials } from './xds-credentials';
@@ -61,4 +62,5 @@ export function register() {
   typed_struct_lb.setup();
   pick_first_lb.setup();
   weighted_round_robin_lb.setup();
+  wrr_locality.setup();
 }

packages/grpc-js-xds/src/lb-policy-registry/wrr-locality.ts

@@ -0,0 +1,75 @@
+/*
+ * Copyright 2025 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+import { LoadBalancingConfig } from "@grpc/grpc-js";
+import { LoadBalancingPolicy__Output } from "../generated/envoy/config/cluster/v3/LoadBalancingPolicy";
+import { TypedExtensionConfig__Output } from "../generated/envoy/config/core/v3/TypedExtensionConfig";
+import { loadProtosWithOptionsSync } from "@grpc/proto-loader/build/src/util";
+import { Any__Output } from "../generated/google/protobuf/Any";
+import { registerLbPolicy } from "../lb-policy-registry";
+import { WrrLocality__Output } from "../generated/envoy/extensions/load_balancing_policies/wrr_locality/v3/WrrLocality";
+
+const WRR_LOCALITY_TYPE_URL = 'envoy.extensions.load_balancing_policies.wrr_locality.v3.WrrLocality';
+
+const resourceRoot = loadProtosWithOptionsSync([
+  'envoy/extensions/load_balancing_policies/wrr_locality/v3/wrr_locality.proto'], {
+    keepCase: true,
+    includeDirs: [
+      // Paths are relative to src/build/lb-policy-registry
+      __dirname + '/../../../deps/envoy-api/',
+      __dirname + '/../../../deps/xds/',
+      __dirname + '/../../../deps/protoc-gen-validate'
+    ],
+  }
+);
+
+const toObjectOptions = {
+  longs: String,
+  enums: String,
+  defaults: true,
+  oneofs: true
+}
+
+function decodePickFirstConfig(message: Any__Output): WrrLocality__Output {
+  const name = message.type_url.substring(message.type_url.lastIndexOf('/') + 1);
+  const type = resourceRoot.lookup(name);
+  if (type) {
+    const decodedMessage = (type as any).decode(message.value);
+    return decodedMessage.$type.toObject(decodedMessage, toObjectOptions) as WrrLocality__Output;
+  } else {
+    throw new Error(`WRR Locality parsing error: unexpected type URL ${message.type_url}`);
+  }
+}
+
+function convertToLoadBalancingPolicy(protoPolicy: TypedExtensionConfig__Output, selectChildPolicy: (childPolicy: LoadBalancingPolicy__Output) => LoadBalancingConfig): LoadBalancingConfig | null {
+  if (protoPolicy.typed_config?.type_url !== WRR_LOCALITY_TYPE_URL) {
+    throw new Error(`WRR Locality LB policy parsing error: unexpected type URL ${protoPolicy.typed_config?.type_url}`);
+  }
+  const wrrLocalityMessage = decodePickFirstConfig(protoPolicy.typed_config);
+  if (!wrrLocalityMessage.endpoint_picking_policy) {
+    throw new Error('WRR Locality LB policy parsing error: no endpoint_picking_policy set');
+  }
+  return {
+    wrr_locality: {
+      shuffleAddressList: selectChildPolicy(wrrLocalityMessage.endpoint_picking_policy)
+    }
+  };
+}
+
+export function setup() {
+  registerLbPolicy(WRR_LOCALITY_TYPE_URL, convertToLoadBalancingPolicy);
+}