googleapis: Allow user set c2p bootstrap config (#9856)

Instead of always overriding the bootstrap with a custom c2p config, now
we allow user defined ones to also be used. This only applies when
running in GCP with federation.

Author: temawi

googleapis/src/main/java/io/grpc/googleapis/GoogleCloudToProdNameResolver.java

@@ -156,22 +156,28 @@ private void resolve() {
     class Resolve implements Runnable {
       @Override
       public void run() {
-        String zone;
-        boolean supportIpv6;
         ImmutableMap<String, ?> rawBootstrap = null;
         try {
-          zone = queryZoneMetadata(METADATA_URL_ZONE);
-          supportIpv6 = queryIpv6SupportMetadata(METADATA_URL_SUPPORT_IPV6);
-          rawBootstrap = generateBootstrap(zone, supportIpv6);
+          // User provided bootstrap configs are only supported with federation. If federation is
+          // not enabled or there is no user provided config, we set a custom bootstrap override.
+          // Otherwise, we don't set the override, which will allow a user provided bootstrap config
+          // to take effect.
+          if (!enableFederation || !xdsBootstrapProvided) {
+            rawBootstrap = generateBootstrap(queryZoneMetadata(METADATA_URL_ZONE),
+                queryIpv6SupportMetadata(METADATA_URL_SUPPORT_IPV6));
+          }
         } catch (IOException e) {
-          listener.onError(Status.INTERNAL.withDescription("Unable to get metadata").withCause(e));
+          listener.onError(
+              Status.INTERNAL.withDescription("Unable to get metadata").withCause(e));
         } finally {
           final ImmutableMap<String, ?> finalRawBootstrap = rawBootstrap;
           syncContext.execute(new Runnable() {
             @Override
             public void run() {
-              if (!shutdown && finalRawBootstrap != null) {
-                bootstrapSetter.setBootstrap(finalRawBootstrap);
+              if (!shutdown) {
+                if (finalRawBootstrap != null) {
+                  bootstrapSetter.setBootstrap(finalRawBootstrap);
+                }
                 delegate.start(listener);
                 succeeded = true;
               }

googleapis/src/test/java/io/grpc/googleapis/GoogleCloudToProdNameResolverTest.java

@@ -195,9 +195,9 @@ public void onGcpAndNoProvidedBootstrapDelegateToXds() {
 
   @SuppressWarnings("unchecked")
   @Test
-  public void onGcpAndProvidedBootstrapAndFederationEnabledDelegateToXds() {
+  public void onGcpAndNoProvidedBootstrapAndFederationEnabledDelegateToXds() {
     GoogleCloudToProdNameResolver.isOnGcp = true;
-    GoogleCloudToProdNameResolver.xdsBootstrapProvided = true;
+    GoogleCloudToProdNameResolver.xdsBootstrapProvided = false;
     GoogleCloudToProdNameResolver.enableFederation = true;
     createResolver();
     resolver.start(mockListener);
@@ -223,6 +223,21 @@ public void onGcpAndProvidedBootstrapAndFederationEnabledDelegateToXds() {
         ImmutableMap.of("xds_servers", ImmutableList.of(server)));
   }
 
+  @SuppressWarnings("unchecked")
+  @Test
+  public void onGcpAndProvidedBootstrapAndFederationEnabledDontDelegateToXds() {
+    GoogleCloudToProdNameResolver.isOnGcp = true;
+    GoogleCloudToProdNameResolver.xdsBootstrapProvided = true;
+    GoogleCloudToProdNameResolver.enableFederation = true;
+    createResolver();
+    resolver.start(mockListener);
+    fakeExecutor.runDueTasks();
+    assertThat(delegatedResolver.keySet()).containsExactly("xds");
+    verify(Iterables.getOnlyElement(delegatedResolver.values())).start(mockListener);
+    // Bootstrapper should not have been set, since there was no user provided config.
+    assertThat(fakeBootstrapSetter.bootstrapRef.get()).isNull();
+  }
+
   @Test
   public void failToQueryMetadata() {
     GoogleCloudToProdNameResolver.isOnGcp = true;