grpc-js: Implement weighted_round_robin LB policy

packages/grpc-js/package.json

@@ -64,7 +64,7 @@
     "pretest": "npm run generate-types && npm run generate-test-types && npm run compile",
     "posttest": "npm run check && madge -c ./build/src",
     "generate-types": "proto-loader-gen-types --keepCase --longs String --enums String --defaults --oneofs --includeComments --includeDirs proto/ --include-dirs proto/ proto/xds/ proto/protoc-gen-validate/ -O src/generated/ --grpcLib ../index channelz.proto xds/service/orca/v3/orca.proto",
-    "generate-test-types": "proto-loader-gen-types --keepCase --longs String --enums String --defaults --oneofs --includeComments --include-dirs test/fixtures/ -O test/generated/ --grpcLib ../../src/index test_service.proto",
+    "generate-test-types": "proto-loader-gen-types --keepCase --longs String --enums String --defaults --oneofs --includeComments --include-dirs test/fixtures/ -O test/generated/ --grpcLib ../../src/index test_service.proto echo_service.proto",
     "copy-protos": "node ./copy-protos"
   },
   "dependencies": {

packages/grpc-js/src/duration.ts

@@ -58,3 +58,18 @@ export function parseDuration(value: string): Duration | null {
     nanos: match[2] ? Number.parseInt(match[2].padEnd(9, '0'), 10) : 0
   };
 }
+
+export function durationToString(duration: Duration): string {
+  if (duration.nanos === 0) {
+    return `${duration.seconds}s`;
+  }
+  let scaleFactor: number;
+  if (duration.nanos % 1_000_000 === 0) {
+    scaleFactor = 1_000_000;
+  } else if (duration.nanos % 1_000 === 0) {
+    scaleFactor = 1_000;
+  } else {
+    scaleFactor = 1;
+  }
+  return `${duration.seconds}.${duration.nanos/scaleFactor}s`;
+}

packages/grpc-js/src/index.ts

@@ -296,6 +296,7 @@ import * as resolver_ip from './resolver-ip';
 import * as load_balancer_pick_first from './load-balancer-pick-first';
 import * as load_balancer_round_robin from './load-balancer-round-robin';
 import * as load_balancer_outlier_detection from './load-balancer-outlier-detection';
+import * as load_balancer_weighted_round_robin from './load-balancer-weighted-round-robin';
 import * as channelz from './channelz';
 import { Deadline } from './deadline';
 
@@ -306,5 +307,6 @@ import { Deadline } from './deadline';
   load_balancer_pick_first.setup();
   load_balancer_round_robin.setup();
   load_balancer_outlier_detection.setup();
+  load_balancer_weighted_round_robin.setup();
   channelz.setup();
 })();

packages/grpc-js/src/load-balancer-pick-first.ts

@@ -588,6 +588,11 @@ export class PickFirstLoadBalancer implements LoadBalancer {
   destroy() {
     this.resetSubchannelList();
     this.removeCurrentPick();
+    this.metricsCall?.cancel();
+    this.metricsCall = null;
+    this.orcaClient?.close();
+    this.orcaClient = null;
+    this.metricsBackoffTimer.stop();
   }
 
   getTypeName(): string {