From 6c12c2bd2438551dc19bd941d158c065eed9e37c Mon Sep 17 00:00:00 2001
From: Eric Anderson <ejona@google.com>
Date: Mon, 6 Jan 2025 10:24:42 -0800
Subject: [PATCH] xds: Remember nonces for unknown types

If the control plane sends a resource type the client doesn't understand
at-the-moment, the control plane will still expect the client to include
the nonce if the client subscribes to the type in the future.

This most easily happens when unsubscribing the last resource of a type.
Which meant 1cf1927d1 was insufficient.
---
 .../main/java/io/grpc/xds/client/ControlPlaneClient.java  | 8 ++++----
 .../test/java/io/grpc/xds/GrpcXdsClientImplTestBase.java  | 5 ++++-
 2 files changed, 8 insertions(+), 5 deletions(-)

diff --git a/xds/src/main/java/io/grpc/xds/client/ControlPlaneClient.java b/xds/src/main/java/io/grpc/xds/client/ControlPlaneClient.java
index 878f1686a8..278bf8b80e 100644
--- a/xds/src/main/java/io/grpc/xds/client/ControlPlaneClient.java
+++ b/xds/src/main/java/io/grpc/xds/client/ControlPlaneClient.java
@@ -309,7 +309,7 @@ final class ControlPlaneClient {
     private boolean responseReceived;
     private boolean sentInitialRequest;
     private boolean closed;
-    // Response nonce for the most recently received discovery responses of each resource type.
+    // Response nonce for the most recently received discovery responses of each resource type URL.
     // Client initiated requests start response nonce with empty string.
     // Nonce in each response is echoed back in the following ACK/NACK request. It is
     // used for management server to identify which response the client is ACKing/NACking.
@@ -318,7 +318,7 @@ final class ControlPlaneClient {
     // map; nonces are only discarded once the stream closes because xds_protocol says "the
     // management server should not send a DiscoveryResponse for any DiscoveryRequest that has a
     // stale nonce."
-    private final Map<XdsResourceType<?>, String> respNonces = new HashMap<>();
+    private final Map<String, String> respNonces = new HashMap<>();
     private final StreamingCall<DiscoveryRequest, DiscoveryResponse> call;
     private final MethodDescriptor<DiscoveryRequest, DiscoveryResponse> methodDescriptor =
         AggregatedDiscoveryServiceGrpc.getStreamAggregatedResourcesMethod();
@@ -369,7 +369,7 @@ final class ControlPlaneClient {
     final void sendDiscoveryRequest(XdsResourceType<?> type, Collection<String> resources) {
       logger.log(XdsLogLevel.INFO, "Sending {0} request for resources: {1}", type, resources);
       sendDiscoveryRequest(type, versions.getOrDefault(type, ""), resources,
-          respNonces.getOrDefault(type, ""), null);
+          respNonces.getOrDefault(type.typeUrl(), ""), null);
     }
 
     @Override
@@ -400,6 +400,7 @@ final class ControlPlaneClient {
           boolean isFirstResponse = !responseReceived;
           responseReceived = true;
           inError = false;
+          respNonces.put(response.getTypeUrl(), response.getNonce());
 
           XdsResourceType<?> type = fromTypeUrl(response.getTypeUrl());
           if (logger.isLoggable(XdsLogLevel.DEBUG)) {
@@ -433,7 +434,6 @@ final class ControlPlaneClient {
                                  String nonce, boolean isFirstResponse) {
       checkNotNull(type, "type");
 
-      respNonces.put(type, nonce);
       ProcessingTracker processingTracker = new ProcessingTracker(
           () -> call.startRecvMessage(), syncContext);
       xdsResponseHandler.handleResourceResponse(type, serverInfo, versionInfo, resources, nonce,
diff --git a/xds/src/test/java/io/grpc/xds/GrpcXdsClientImplTestBase.java b/xds/src/test/java/io/grpc/xds/GrpcXdsClientImplTestBase.java
index 9a80e3c36b..00fbfe669a 100644
--- a/xds/src/test/java/io/grpc/xds/GrpcXdsClientImplTestBase.java
+++ b/xds/src/test/java/io/grpc/xds/GrpcXdsClientImplTestBase.java
@@ -2898,10 +2898,13 @@ public abstract class GrpcXdsClientImplTestBase {
     xdsClient.cancelXdsResourceWatch(XdsEndpointResource.getInstance(), "A.1", edsResourceWatcher);
     verifySubscribedResourcesMetadataSizes(0, 0, 0, 0);
     call.verifyRequest(EDS, Arrays.asList(), VERSION_1, "0000", NODE);
+    // The control plane can send an updated response for the empty subscription list, with a new
+    // nonce.
+    call.sendResponse(EDS, Arrays.asList(), VERSION_1, "0001");
 
     // When re-subscribing, the version was forgotten but not the nonce
     xdsClient.watchXdsResource(XdsEndpointResource.getInstance(), "A.1", edsResourceWatcher);
-    call.verifyRequest(EDS, "A.1", "", "0000", NODE, Mockito.timeout(2000));
+    call.verifyRequest(EDS, "A.1", "", "0001", NODE, Mockito.timeout(2000));
   }
 
   @Test