xds: override bootstrap for xds server

xds/src/main/java/io/grpc/xds/XdsServerBuilder.java

@@ -22,7 +22,6 @@
 import static io.grpc.xds.InternalXdsAttributes.ATTR_DRAIN_GRACE_NANOS;
 import static io.grpc.xds.InternalXdsAttributes.ATTR_FILTER_CHAIN_SELECTOR_MANAGER;
 
-import com.google.common.annotations.VisibleForTesting;
 import com.google.errorprone.annotations.DoNotCall;
 import io.grpc.Attributes;
 import io.grpc.ExperimentalApi;
@@ -37,9 +36,12 @@
 import io.grpc.netty.NettyServerBuilder;
 import io.grpc.xds.FilterChainMatchingProtocolNegotiators.FilterChainMatchingNegotiatorServerFactory;
 import io.grpc.xds.XdsNameResolverProvider.XdsClientPoolFactory;
+
+import java.util.Map;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.logging.Logger;
+import javax.annotation.Nullable;
 
 /**
  * A version of {@link ServerBuilder} to create xDS managed servers.
@@ -130,9 +132,18 @@ public Server build() {
             filterChainSelectorManager, xdsClientPoolFactory, filterRegistry);
   }
 
-  @VisibleForTesting
-  XdsServerBuilder xdsClientPoolFactory(XdsClientPoolFactory xdsClientPoolFactory) {
-    this.xdsClientPoolFactory = checkNotNull(xdsClientPoolFactory, "xdsClientPoolFactory");
+  /**
+   * Allows injecting {@link XdsClientPoolFactory} and/or overriding bootstrap configuration, useful
+   * for testing.
+   */
+  public XdsServerBuilder xdsClientPoolFactory(@Nullable XdsClientPoolFactory xdsClientPoolFactory,
+                                        @Nullable Map<String, ?> bootstrapOverride) {
+    if (xdsClientPoolFactory != null) {
+      this.xdsClientPoolFactory = xdsClientPoolFactory;
+    }
+    if (bootstrapOverride != null) {
+      this.xdsClientPoolFactory.setBootstrapOverride(bootstrapOverride);
+    }
     return this;
   }
 

xds/src/test/java/io/grpc/xds/XdsSdsClientServerTest.java

@@ -337,7 +337,7 @@ private void buildServerWithFallbackServerCredentials(
       throws Exception {
     ServerCredentials xdsCredentials = XdsServerCredentials.create(fallbackCredentials);
     XdsServerBuilder builder = XdsServerBuilder.forPort(0, xdsCredentials)
-            .xdsClientPoolFactory(fakePoolFactory)
+            .xdsClientPoolFactory(fakePoolFactory, null)
             .addService(new SimpleServiceImpl());
     buildServer(builder, downstreamTlsContext);
   }

xds/src/test/java/io/grpc/xds/XdsServerBuilderTest.java

@@ -77,7 +77,7 @@ private void buildBuilder(XdsServerBuilder.XdsServingStatusListener xdsServingSt
     builder =
         XdsServerBuilder.forPort(
             port, XdsServerCredentials.create(InsecureServerCredentials.create()));
-    builder.xdsClientPoolFactory(new FakeXdsClientPoolFactory(xdsClient));
+    builder.xdsClientPoolFactory(new FakeXdsClientPoolFactory(xdsClient), null);
     if (xdsServingStatusListener != null) {
       builder.xdsServingStatusListener(xdsServingStatusListener);
     }