Let xDS load balancer bootstrap from a bootstrap file. Currently not use configurations from bootstrap in xDS communication as the xDS load balancer implementation is undergoing changes. We will integrate it later.

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

@@ -71,6 +71,12 @@ final class XdsLoadBalancer extends LoadBalancer {
   private LoadReportClient lrsClient;
   @Nullable
   private XdsLbState xdsLbState;
+
+  // TODO(chengyuanzhang): use information populated by bootstrapper in xDS communication after
+  //  xDS load balancer restructure is done. For now, don't integrate it.
+  @SuppressWarnings("unused")
+  @Nullable
+  private Bootstrapper bootstrapper;
   private final AdsStreamCallback adsStreamCallback = new AdsStreamCallback() {
 
     @Override
@@ -112,24 +118,27 @@ final class XdsLoadBalancer extends LoadBalancer {
   private LbConfig fallbackPolicy;
 
   XdsLoadBalancer(Helper helper, LoadBalancerRegistry lbRegistry,
-      BackoffPolicy.Provider backoffPolicyProvider) {
+      BackoffPolicy.Provider backoffPolicyProvider, boolean usingBootstrap) {
-    this(helper, lbRegistry, backoffPolicyProvider, LoadReportClientFactory.getInstance(),
+    this(helper, lbRegistry, backoffPolicyProvider, usingBootstrap,
-        new FallbackManager(helper, lbRegistry));
+        LoadReportClientFactory.getInstance(), new FallbackManager(helper, lbRegistry));
   }
 
   private XdsLoadBalancer(Helper helper,
       LoadBalancerRegistry lbRegistry,
       BackoffPolicy.Provider backoffPolicyProvider,
+      boolean usingBootstrap,
       LoadReportClientFactory lrsClientFactory,
       FallbackManager fallbackManager) {
-    this(helper, lbRegistry, backoffPolicyProvider, lrsClientFactory, fallbackManager,
+    this(helper, lbRegistry, backoffPolicyProvider, usingBootstrap, lrsClientFactory,
-        new LocalityStoreImpl(new LocalityStoreHelper(helper, fallbackManager), lbRegistry));
+        fallbackManager, new LocalityStoreImpl(new LocalityStoreHelper(helper, fallbackManager),
+            lbRegistry));
   }
 
   @VisibleForTesting
   XdsLoadBalancer(Helper helper,
       LoadBalancerRegistry lbRegistry,
       BackoffPolicy.Provider backoffPolicyProvider,
+      boolean usingBootstrap,
       LoadReportClientFactory lrsClientFactory,
       FallbackManager fallbackManager,
       LocalityStore localityStore) {
@@ -139,6 +148,16 @@ final class XdsLoadBalancer extends LoadBalancer {
     this.lrsClientFactory = checkNotNull(lrsClientFactory, "lrsClientFactory");
     this.fallbackManager = checkNotNull(fallbackManager, "fallbackManager");
     this.localityStore = checkNotNull(localityStore, "localityStore");
+    if (usingBootstrap) {
+      // TODO(chengyuanzhang): figure out error handling when bootstrap fails. Currently bootstrap
+      //  has not been integrated, but we do need a clear way of handling this case.
+      try {
+        bootstrapper = Bootstrapper.getInstance();
+      } catch (Exception e) {
+        helper.getChannelLogger()
+            .log(ChannelLogLevel.ERROR, "Unable to bootstrap from local bootstrap file.");
+      }
+    }
   }
 
   private static final class LocalityStoreHelper extends ForwardingLoadBalancerHelper {

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

@@ -67,7 +67,7 @@ public final class XdsLoadBalancerProvider extends LoadBalancerProvider {
   @Override
   public LoadBalancer newLoadBalancer(Helper helper) {
     return new XdsLoadBalancer(helper, LoadBalancerRegistry.getDefaultRegistry(),
-        new ExponentialBackoffPolicy.Provider());
+        new ExponentialBackoffPolicy.Provider(), false);
   }
 
   @Override

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

@@ -227,7 +227,7 @@ public class XdsLoadBalancerTest {
     lbRegistry.register(lbProvider1);
     lbRegistry.register(lbProvider2);
     lbRegistry.register(roundRobin);
-    lb = new XdsLoadBalancer(helper, lbRegistry, backoffPolicyProvider);
+    lb = new XdsLoadBalancer(helper, lbRegistry, backoffPolicyProvider, false);
     doReturn(syncContext).when(helper).getSynchronizationContext();
     doReturn(fakeClock.getScheduledExecutorService()).when(helper).getScheduledExecutorService();
     doReturn(mock(ChannelLogger.class)).when(helper).getChannelLogger();

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

@@ -224,7 +224,7 @@ public class XdsLoadBalancerWithLrsTest {
         any(BackoffPolicy.Provider.class), any(LoadStatsStore.class))).thenReturn(lrsClient);
 
     xdsLoadBalancer =
-        new XdsLoadBalancer(helper, lbRegistry, backoffPolicyProvider, lrsClientFactory,
+        new XdsLoadBalancer(helper, lbRegistry, backoffPolicyProvider, false, lrsClientFactory,
             new FallbackManager(helper, lbRegistry), localityStore);
   }