snapshot of https://github.com/grpc/grpc-go.git (master, 2026-09-15; blobs > 131072B omitted)

internal/xds/balancer/cdsbalancer/e2e_test/dns_impl_test.go

@@ -0,0 +1,136 @@
+/*
+ * Copyright 2026 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 e2e_test
+
+import (
+	"context"
+	"fmt"
+	"testing"
+
+	"github.com/google/uuid"
+	"google.golang.org/grpc"
+	"google.golang.org/grpc/credentials/insecure"
+	"google.golang.org/grpc/internal"
+	"google.golang.org/grpc/internal/stubserver"
+	"google.golang.org/grpc/internal/testutils/xds/e2e"
+	"google.golang.org/grpc/peer"
+	"google.golang.org/grpc/resolver"
+	"google.golang.org/grpc/resolver/manual"
+
+	v3clusterpb "github.com/envoyproxy/go-control-plane/envoy/config/cluster/v3"
+	v3listenerpb "github.com/envoyproxy/go-control-plane/envoy/config/listener/v3"
+	v3routepb "github.com/envoyproxy/go-control-plane/envoy/config/route/v3"
+	testgrpc "google.golang.org/grpc/interop/grpc_testing"
+	testpb "google.golang.org/grpc/interop/grpc_testing"
+
+	_ "google.golang.org/grpc/internal/xds/balancer/priority" // Register priority LB policy.
+)
+
+// TestLogicalDNS_MultipleEndpoints tests the priority LB policy using a
+// LOGICAL_DNS discovery mechanism.
+//
+// The test verifies that multiple addresses returned by the DNS resolver are
+// grouped into a single endpoint (as per gRFC A61). Because the round_robin LB
+// policy sees only one endpoint, it should not rotate traffic between the
+// addresses. Instead, the single endpoint is picked, and connects to the first
+// address.
+func (s) TestLogicalDNS_MultipleEndpoints(t *testing.T) {
+	// Spin up a management server to receive xDS resources from.
+	managementServer := e2e.StartManagementServer(t, e2e.ManagementServerOptions{})
+
+	// Create bootstrap configuration pointing to the above management server.
+	nodeID := uuid.New().String()
+	bootstrapContents := e2e.DefaultBootstrapContents(t, nodeID, managementServer.Address)
+	resolverBuilder, err := internal.NewXDSResolverWithConfigForTesting.(func([]byte) (resolver.Builder, error))(bootstrapContents)
+	if err != nil {
+		t.Fatalf("Failed to create xDS resolver for testing: %v", err)
+	}
+
+	// Start backend servers which provide an implementation of the TestService.
+	server1 := stubserver.StartTestService(t, nil)
+	defer server1.Stop()
+	server2 := stubserver.StartTestService(t, nil)
+	defer server2.Stop()
+
+	// Register a manual resolver with the "dns" scheme to override DNS resolution.
+	// This global override is safe because connection to the xDS management
+	// server uses the passthrough scheme instead and therefore overriding
+	// the DNS resolver does not affect it in any way.
+	const dnsScheme = "dns"
+	dnsR := manual.NewBuilderWithScheme(dnsScheme)
+	originalDNS := resolver.Get("dns")
+	resolver.Register(dnsR)
+	t.Cleanup(func() { resolver.Register(originalDNS) })
+
+	// For LOGICAL_DNS, this updates the SINGLE endpoint to have 2 IPs.
+	dnsR.InitialState(resolver.State{
+		Endpoints: []resolver.Endpoint{{
+			Addresses: []resolver.Address{
+				{Addr: server1.Address},
+				{Addr: server2.Address},
+			}}},
+	})
+
+	const (
+		serviceName   = "test-xds-service"
+		clusterName   = "cluster-test-xds-service"
+		endpointsName = "endpoints-test-xds-service"
+		rdsName       = "route-test-xds-service"
+	)
+
+	resources := e2e.UpdateOptions{
+		NodeID:    nodeID,
+		Listeners: []*v3listenerpb.Listener{e2e.DefaultClientListener(serviceName, rdsName)},
+		Routes:    []*v3routepb.RouteConfiguration{e2e.DefaultRouteConfig(rdsName, serviceName, clusterName)},
+		Clusters: []*v3clusterpb.Cluster{e2e.ClusterResourceWithOptions(e2e.ClusterOptions{
+			ClusterName: clusterName,
+			ServiceName: endpointsName,
+			Type:        e2e.ClusterTypeLogicalDNS,
+			DNSHostName: "dns",
+			DNSPort:     uint32(8080),
+			Policy:      e2e.LoadBalancingPolicyRoundRobin,
+		})},
+		Endpoints: nil,
+	}
+
+	ctx, cancel := context.WithTimeout(context.Background(), defaultTestTimeout)
+	defer cancel()
+
+	if err := managementServer.Update(ctx, resources); err != nil {
+		t.Fatalf("Failed to update management server: %v", err)
+	}
+
+	// Create a ClientConn and make a successful RPC.
+	cc, err := grpc.NewClient(fmt.Sprintf("xds:///"+serviceName), grpc.WithTransportCredentials(insecure.NewCredentials()), grpc.WithResolvers(resolverBuilder))
+	if err != nil {
+		t.Fatalf("Failed to create new client for local test server: %v", err)
+	}
+	defer cc.Close()
+
+	// Ensure the RPC is routed to the first backend.
+	testClient := testgrpc.NewTestServiceClient(cc)
+	for i := 0; i < 10; i++ {
+		var peer peer.Peer
+		if _, err := testClient.EmptyCall(ctx, &testpb.Empty{}, grpc.Peer(&peer)); err != nil {
+			t.Fatalf("RPC failed: %v", err)
+		}
+
+		if got, want := peer.Addr.String(), server1.Address; got != want {
+			t.Errorf("peer.Addr = %q, want = %q", got, want)
+		}
+	}
+}