balancer: populate endpoint weight by edsbalancer for weighted_round_…

…robin (#2945)

balancer/weightedroundrobin/weightedroundrobin.go

@@ -0,0 +1,29 @@
+/*
+ *
+ * Copyright 2019 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.
+ *
+ */
+
+// Package weightedroundrobin defines a weighted roundrobin balancer.
+package weightedroundrobin
+
+// Name is the name of weighted_round_robin balancer.
+const Name = "weighted_round_robin"
+
+// AddrInfo will be stored inside Address metadata in order to use weighted roundrobin
+// balancer.
+type AddrInfo struct {
+	Weight uint32
+}

balancer/xds/edsbalancer/edsbalancer.go

@@ -27,6 +27,7 @@ import (
 
 	"google.golang.org/grpc/balancer"
 	"google.golang.org/grpc/balancer/roundrobin"
+	"google.golang.org/grpc/balancer/weightedroundrobin"
 	"google.golang.org/grpc/balancer/xds/internal"
 	edspb "google.golang.org/grpc/balancer/xds/internal/proto/envoy/api/v2/eds"
 	endpointpb "google.golang.org/grpc/balancer/xds/internal/proto/envoy/api/v2/endpoint/endpoint"
@@ -227,9 +228,16 @@ func (xdsB *EDSBalancer) HandleEDSResponse(edsResp *edspb.ClusterLoadAssignment)
 		var newAddrs []resolver.Address
 		for _, lbEndpoint := range locality.GetLbEndpoints() {
 			socketAddress := lbEndpoint.GetEndpoint().GetAddress().GetSocketAddress()
-			newAddrs = append(newAddrs, resolver.Address{
+			address := resolver.Address{
 				Addr: net.JoinHostPort(socketAddress.GetAddress(), strconv.Itoa(int(socketAddress.GetPortValue()))),
-			})
+			}
+			if xdsB.subBalancerBuilder.Name() == weightedroundrobin.Name &&
+				lbEndpoint.GetLoadBalancingWeight().GetValue() != 0 {
+				address.Metadata = &weightedroundrobin.AddrInfo{
+					Weight: lbEndpoint.GetLoadBalancingWeight().GetValue(),
+				}
+			}
+			newAddrs = append(newAddrs, address)
 		}
 		var weightChanged, addrsChanged bool
 		config, ok := xdsB.lidToConfig[lid]