Add xDS e2e test

balancer/leastrequest/leastrequest.go

@@ -31,7 +31,7 @@ import (
 	"google.golang.org/grpc/serviceconfig"
 )
 
-// Global to stub out in tests.
+// grpcranduint32 is a global to stub out in tests.
 var grpcranduint32 = grpcrand.Uint32
 
 // Name is the name of the least request balancer.

test/xds/xds_client_custom_lb_test.go

@@ -25,6 +25,7 @@ import (
 	"time"
 
 	"google.golang.org/grpc"
+	_ "google.golang.org/grpc/balancer/leastrequest"       // To register least_request
 	_ "google.golang.org/grpc/balancer/weightedroundrobin" // To register weighted_round_robin
 	"google.golang.org/grpc/credentials/insecure"
 	"google.golang.org/grpc/internal/envconfig"
@@ -41,6 +42,7 @@ import (
 	v3listenerpb "github.com/envoyproxy/go-control-plane/envoy/config/listener/v3"
 	v3routepb "github.com/envoyproxy/go-control-plane/envoy/config/route/v3"
 	v3clientsideweightedroundrobinpb "github.com/envoyproxy/go-control-plane/envoy/extensions/load_balancing_policies/client_side_weighted_round_robin/v3"
+	v3leastrequestpb "github.com/envoyproxy/go-control-plane/envoy/extensions/load_balancing_policies/least_request/v3"
 	v3roundrobinpb "github.com/envoyproxy/go-control-plane/envoy/extensions/load_balancing_policies/round_robin/v3"
 	v3wrrlocalitypb "github.com/envoyproxy/go-control-plane/envoy/extensions/load_balancing_policies/wrr_locality/v3"
 	"github.com/golang/protobuf/proto"
@@ -96,6 +98,11 @@ func (s) TestWrrLocality(t *testing.T) {
 	defer func() {
 		envconfig.XDSCustomLBPolicy = oldCustomLBSupport
 	}()
+	oldLeastRequestLBSupport := envconfig.LeastRequestLB
+	envconfig.LeastRequestLB = true
+	defer func() {
+		envconfig.LeastRequestLB = oldLeastRequestLBSupport
+	}()
 
 	backend1 := stubserver.StartTestService(t, nil)
 	port1 := testutils.ParsePort(t, backend1.Address)
@@ -194,12 +201,31 @@ func (s) TestWrrLocality(t *testing.T) {
 				{addr: backend5.Address, count: 8},
 			},
 		},
+		{
+			name: "custom_lb_least_request",
+			wrrLocalityConfiguration: wrrLocality(&v3leastrequestpb.LeastRequest{
+				ChoiceCount: wrapperspb.UInt32(2),
+			}),
+			// Least request's randomness of indexes to sample (unary RPCs which
+			// don't persist so never any actual RPC counts over iterations)
+			// converges onto a round robin distribution per locality. Thus,
+			// expect the same distribution as round robin above.
+			addressDistributionWant: []struct {
+				addr  string
+				count int
+			}{
+				{addr: backend1.Address, count: 6},
+				{addr: backend2.Address, count: 6},
+				{addr: backend3.Address, count: 8},
+				{addr: backend4.Address, count: 8},
+				{addr: backend5.Address, count: 8},
+			},
+		},
 	}
 	for _, test := range tests {
 		t.Run(test.name, func(t *testing.T) {
 			managementServer, nodeID, _, r, cleanup := e2e.SetupManagementServer(t, e2e.ManagementServerOptions{})
 			defer cleanup()
-
 			routeConfigName := "route-" + serviceName
 			clusterName := "cluster-" + serviceName
 			endpointsName := "endpoints-" + serviceName

xds/internal/balancer/balancer.go

@@ -20,6 +20,7 @@
 package balancer
 
 import (
+	_ "google.golang.org/grpc/balancer/leastrequest"                  // Register the least_request_experimental balancer
 	_ "google.golang.org/grpc/balancer/weightedtarget"                // Register the weighted_target balancer
 	_ "google.golang.org/grpc/xds/internal/balancer/cdsbalancer"      // Register the CDS balancer
 	_ "google.golang.org/grpc/xds/internal/balancer/clusterimpl"      // Register the xds_cluster_impl balancer

xds/internal/xdsclient/xdslbregistry/converter/converter.go

@@ -30,9 +30,9 @@ import (
 	"github.com/golang/protobuf/proto"
 	"google.golang.org/grpc"
 	"google.golang.org/grpc/balancer"
+	"google.golang.org/grpc/balancer/leastrequest"
 	"google.golang.org/grpc/balancer/roundrobin"
 	"google.golang.org/grpc/balancer/weightedroundrobin"
-	"google.golang.org/grpc/internal/balancer/leastrequest"
 	"google.golang.org/grpc/internal/envconfig"
 	internalserviceconfig "google.golang.org/grpc/internal/serviceconfig"
 	"google.golang.org/grpc/xds/internal/balancer/ringhash"

xds/internal/xdsclient/xdsresource/tests/unmarshal_cds_test.go

@@ -25,8 +25,8 @@ import (
 
 	"github.com/google/go-cmp/cmp"
 	"github.com/google/go-cmp/cmp/cmpopts"
+	"google.golang.org/grpc/balancer/leastrequest"
 	_ "google.golang.org/grpc/balancer/roundrobin" // To register round_robin load balancer.
-	"google.golang.org/grpc/internal/balancer/leastrequest"
 	"google.golang.org/grpc/internal/balancer/stub"
 	"google.golang.org/grpc/internal/envconfig"
 	"google.golang.org/grpc/internal/grpctest"