xdsclient: correct logic used to suppress empty ADS requests on new streams

xds/internal/xdsclient/transport/transport.go

@@ -363,29 +363,21 @@ func (t *Transport) send(ctx context.Context) {
 	// The xDS protocol only requires that we send the node proto in the first
 	// discovery request on every stream. Sending the node proto in every
 	// request message wastes CPU resources on the client and the server.
-	sendNodeProto := true
+	sentNodeProto := false
 	for {
 		select {
 		case <-ctx.Done():
 			return
 		case stream = <-t.adsStreamCh:
 			// We have a new stream and we've to ensure that the node proto gets
-			// sent out in the first request on the stream. At this point, we
-			// might not have any registered watches. Setting this field to true
-			// here will ensure that the node proto gets sent out along with the
-			// discovery request when the first watch is registered.
-			if len(t.resources) == 0 {
-				sendNodeProto = true
-				continue
-			}
-
-			if !t.sendExisting(stream) {
+			// sent out in the first request on the stream.
+			var err error
+			if sentNodeProto, err = t.sendExisting(stream); err != nil {
 				// Send failed, clear the current stream. Attempt to resend will
 				// only be made after a new stream is created.
 				stream = nil
 				continue
 			}
-			sendNodeProto = false
 		case u, ok := <-t.adsRequestCh.Get():
 			if !ok {
 				// No requests will be sent after the adsRequestCh buffer is closed.
@@ -416,12 +408,12 @@ func (t *Transport) send(ctx context.Context) {
 				// sending response back).
 				continue
 			}
-			if err := t.sendAggregatedDiscoveryServiceRequest(stream, sendNodeProto, resources, url, version, nonce, nackErr); err != nil {
+			if err := t.sendAggregatedDiscoveryServiceRequest(stream, !sentNodeProto, resources, url, version, nonce, nackErr); err != nil {
 				t.logger.Warningf("Sending ADS request for resources: %q, url: %q, version: %q, nonce: %q failed: %v", resources, url, version, nonce, err)
 				// Send failed, clear the current stream.
 				stream = nil
 			}
-			sendNodeProto = false
+			sentNodeProto = true
 		}
 	}
 }
@@ -433,7 +425,9 @@ func (t *Transport) send(ctx context.Context) {
 // that here because the stream has just started and Send() usually returns
 // quickly (once it pushes the message onto the transport layer) and is only
 // ever blocked if we don't have enough flow control quota.
-func (t *Transport) sendExisting(stream adsStream) bool {
+//
+// Returns true if the node proto was sent.
+func (t *Transport) sendExisting(stream adsStream) (sentNodeProto bool, err error) {
 	t.mu.Lock()
 	defer t.mu.Unlock()
 
@@ -450,16 +444,18 @@ func (t *Transport) sendExisting(stream adsStream) bool {
 	t.nonces = make(map[string]string)
 
 	// Send node proto only in the first request on the stream.
-	sendNodeProto := true
 	for url, resources := range t.resources {
-		if err := t.sendAggregatedDiscoveryServiceRequest(stream, sendNodeProto, mapToSlice(resources), url, t.versions[url], "", nil); err != nil {
+		if len(resources) == 0 {
+			continue
+		}
+		if err := t.sendAggregatedDiscoveryServiceRequest(stream, !sentNodeProto, mapToSlice(resources), url, t.versions[url], "", nil); err != nil {
 			t.logger.Warningf("Sending ADS request for resources: %q, url: %q, version: %q, nonce: %q failed: %v", resources, url, t.versions[url], "", err)
-			return false
+			return false, err
 		}
-		sendNodeProto = false
+		sentNodeProto = true
 	}
 
-	return true
+	return sentNodeProto, nil
 }
 
 // recv receives xDS responses on the provided ADS stream and branches out to

xds/internal/xdsclient/transport/transport_resource_test.go

@@ -21,6 +21,7 @@ package transport_test
 
 import (
 	"context"
+	"errors"
 	"testing"
 	"time"
 
@@ -217,3 +218,193 @@ func (s) TestHandleResponseFromManagementServer(t *testing.T) {
 		})
 	}
 }
+
+func (s) TestEmptyListenerResourceOnStreamRestart(t *testing.T) {
+	ctx, cancel := context.WithTimeout(context.Background(), defaultTestTimeout)
+	defer cancel()
+
+	mgmtServer, cleanup := startFakeManagementServer(t)
+	defer cleanup()
+	t.Logf("Started xDS management server on %s", mgmtServer.Address)
+	nodeProto := &v3corepb.Node{Id: uuid.New().String()}
+	tr, err := transport.New(transport.Options{
+		ServerCfg: *xdstestutils.ServerConfigForAddress(t, mgmtServer.Address),
+		OnRecvHandler: func(update transport.ResourceUpdate) error {
+			return nil
+		},
+		OnSendHandler:  func(*transport.ResourceSendInfo) {},                // No onSend handling.
+		OnErrorHandler: func(error) {},                                      // No stream error handling.
+		Backoff:        func(int) time.Duration { return time.Duration(0) }, // No backoff.
+		NodeProto:      nodeProto,
+	})
+	if err != nil {
+		t.Fatalf("Failed to create xDS transport: %v", err)
+	}
+	defer tr.Close()
+
+	// Send a request for a listener resource.
+	const resource = "some-resource"
+	tr.SendRequest(version.V3ListenerURL, []string{resource})
+
+	// Ensure the proper request was sent.
+	val, err := mgmtServer.XDSRequestChan.Receive(ctx)
+	if err != nil {
+		t.Fatalf("Error waiting for mgmt server response: %v", err)
+	}
+	wantReq := &fakeserver.Request{Req: &v3discoverypb.DiscoveryRequest{
+		Node:          nodeProto,
+		ResourceNames: []string{resource},
+		TypeUrl:       "type.googleapis.com/envoy.config.listener.v3.Listener",
+	}}
+	gotReq := val.(*fakeserver.Request)
+	if diff := cmp.Diff(gotReq, wantReq, protocmp.Transform()); diff != "" {
+		t.Fatalf("Discovery request received at management server is %+v, want %+v", gotReq, wantReq)
+	}
+
+	// Remove the subscription by requesting an empty list.
+	tr.SendRequest(version.V3ListenerURL, []string{})
+
+	// Ensure the proper request was sent.
+	val, err = mgmtServer.XDSRequestChan.Receive(ctx)
+	if err != nil {
+		t.Fatalf("Error waiting for mgmt server response: %v", err)
+	}
+	wantReq = &fakeserver.Request{Req: &v3discoverypb.DiscoveryRequest{
+		ResourceNames: []string{},
+		TypeUrl:       "type.googleapis.com/envoy.config.listener.v3.Listener",
+	}}
+	gotReq = val.(*fakeserver.Request)
+	if diff := cmp.Diff(gotReq, wantReq, protocmp.Transform()); diff != "" {
+		t.Fatalf("Discovery request received at management server is %+v, want %+v", gotReq, wantReq)
+	}
+
+	// Cause the stream to restart.
+	mgmtServer.XDSResponseChan <- &fakeserver.Response{Err: errors.New("go away")}
+
+	// Ensure no request is sent since there are no resources.
+	ctxShort, cancel := context.WithTimeout(ctx, defaultTestShortTimeout)
+	defer cancel()
+	if got, err := mgmtServer.XDSRequestChan.Receive(ctxShort); !errors.Is(err, context.DeadlineExceeded) {
+		t.Fatalf("mgmt server received request: %v; wanted DeadlineExceeded error", got)
+	}
+
+	tr.SendRequest(version.V3ListenerURL, []string{resource})
+
+	// Ensure the proper request was sent with the node proto.
+	val, err = mgmtServer.XDSRequestChan.Receive(ctx)
+	if err != nil {
+		t.Fatalf("Error waiting for mgmt server response: %v", err)
+	}
+	wantReq = &fakeserver.Request{Req: &v3discoverypb.DiscoveryRequest{
+		Node:          nodeProto,
+		ResourceNames: []string{resource},
+		TypeUrl:       "type.googleapis.com/envoy.config.listener.v3.Listener",
+	}}
+	gotReq = val.(*fakeserver.Request)
+	if diff := cmp.Diff(gotReq, wantReq, protocmp.Transform()); diff != "" {
+		t.Fatalf("Discovery request received at management server is %+v, want %+v", gotReq, wantReq)
+	}
+
+}
+
+func (s) TestEmptyClusterResourceOnStreamRestartWithListener(t *testing.T) {
+	ctx, cancel := context.WithTimeout(context.Background(), defaultTestTimeout)
+	defer cancel()
+
+	mgmtServer, cleanup := startFakeManagementServer(t)
+	defer cleanup()
+	t.Logf("Started xDS management server on %s", mgmtServer.Address)
+	nodeProto := &v3corepb.Node{Id: uuid.New().String()}
+	tr, err := transport.New(transport.Options{
+		ServerCfg: *xdstestutils.ServerConfigForAddress(t, mgmtServer.Address),
+		OnRecvHandler: func(update transport.ResourceUpdate) error {
+			return nil
+		},
+		OnSendHandler:  func(*transport.ResourceSendInfo) {},                // No onSend handling.
+		OnErrorHandler: func(error) {},                                      // No stream error handling.
+		Backoff:        func(int) time.Duration { return time.Duration(0) }, // No backoff.
+		NodeProto:      nodeProto,
+	})
+	if err != nil {
+		t.Fatalf("Failed to create xDS transport: %v", err)
+	}
+	defer tr.Close()
+
+	// Send a request for a listener resource.
+	const resource = "some-resource"
+	tr.SendRequest(version.V3ListenerURL, []string{resource})
+
+	// Ensure the proper request was sent.
+	val, err := mgmtServer.XDSRequestChan.Receive(ctx)
+	if err != nil {
+		t.Fatalf("Error waiting for mgmt server response: %v", err)
+	}
+	wantReq := &fakeserver.Request{Req: &v3discoverypb.DiscoveryRequest{
+		Node:          nodeProto,
+		ResourceNames: []string{resource},
+		TypeUrl:       "type.googleapis.com/envoy.config.listener.v3.Listener",
+	}}
+	gotReq := val.(*fakeserver.Request)
+	if diff := cmp.Diff(gotReq, wantReq, protocmp.Transform()); diff != "" {
+		t.Fatalf("Discovery request received at management server is %+v, want %+v", gotReq, wantReq)
+	}
+
+	// Send a request for a cluster resource.
+	tr.SendRequest(version.V3ClusterURL, []string{resource})
+
+	// Ensure the proper request was sent.
+	val, err = mgmtServer.XDSRequestChan.Receive(ctx)
+	if err != nil {
+		t.Fatalf("Error waiting for mgmt server response: %v", err)
+	}
+	wantReq = &fakeserver.Request{Req: &v3discoverypb.DiscoveryRequest{
+		ResourceNames: []string{resource},
+		TypeUrl:       "type.googleapis.com/envoy.config.cluster.v3.Cluster",
+	}}
+	gotReq = val.(*fakeserver.Request)
+	if diff := cmp.Diff(gotReq, wantReq, protocmp.Transform()); diff != "" {
+		t.Fatalf("Discovery request received at management server is %+v, want %+v", gotReq, wantReq)
+	}
+
+	// Remove the cluster subscription by requesting an empty list.
+	tr.SendRequest(version.V3ClusterURL, []string{})
+
+	// Ensure the proper request was sent.
+	val, err = mgmtServer.XDSRequestChan.Receive(ctx)
+	if err != nil {
+		t.Fatalf("Error waiting for mgmt server response: %v", err)
+	}
+	wantReq = &fakeserver.Request{Req: &v3discoverypb.DiscoveryRequest{
+		ResourceNames: []string{},
+		TypeUrl:       "type.googleapis.com/envoy.config.cluster.v3.Cluster",
+	}}
+	gotReq = val.(*fakeserver.Request)
+	if diff := cmp.Diff(gotReq, wantReq, protocmp.Transform()); diff != "" {
+		t.Fatalf("Discovery request received at management server is %+v, want %+v", gotReq, wantReq)
+	}
+
+	// Cause the stream to restart.
+	mgmtServer.XDSResponseChan <- &fakeserver.Response{Err: errors.New("go away")}
+
+	// Ensure the proper LDS request was sent.
+	val, err = mgmtServer.XDSRequestChan.Receive(ctx)
+	if err != nil {
+		t.Fatalf("Error waiting for mgmt server response: %v", err)
+	}
+	wantReq = &fakeserver.Request{Req: &v3discoverypb.DiscoveryRequest{
+		Node:          nodeProto,
+		ResourceNames: []string{resource},
+		TypeUrl:       "type.googleapis.com/envoy.config.listener.v3.Listener",
+	}}
+	gotReq = val.(*fakeserver.Request)
+	if diff := cmp.Diff(gotReq, wantReq, protocmp.Transform()); diff != "" {
+		t.Fatalf("Discovery request received at management server is %+v, want %+v", gotReq, wantReq)
+	}
+
+	// Ensure no cluster request is sent since there are no cluster resources.
+	ctxShort, cancel := context.WithTimeout(ctx, defaultTestShortTimeout)
+	defer cancel()
+	if got, err := mgmtServer.XDSRequestChan.Receive(ctxShort); !errors.Is(err, context.DeadlineExceeded) {
+		t.Fatalf("mgmt server received request: %v; wanted DeadlineExceeded error", got)
+	}
+}