Only create hard-coded when it is being used

Author: ejona86

api/src/main/java/io/grpc/InternalServiceProviders.java

@@ -38,7 +38,7 @@ public static <T> List<T> loadAll(
     return loadAll(
         klass,
         ServiceLoader.load(klass, classLoader).iterator(),
-        hardCodedClasses,
+        () -> hardCodedClasses,
         priorityAccessor);
   }
 
@@ -48,9 +48,9 @@ public static <T> List<T> loadAll(
   public static <T> List<T> loadAll(
       Class<T> klass,
       Iterator<T> serviceLoader,
-      Iterable<Class<?>> hardCodedClasses,
+      Supplier<Iterable<Class<?>>> hardCodedClasses,
       PriorityAccessor<T> priorityAccessor) {
-    return ServiceProviders.loadAll(klass, serviceLoader, hardCodedClasses, priorityAccessor);
+    return ServiceProviders.loadAll(klass, serviceLoader, hardCodedClasses::get, priorityAccessor);
   }
 
   /**
@@ -78,4 +78,8 @@ public static boolean isAndroid(ClassLoader cl) {
   }
 
   public interface PriorityAccessor<T> extends ServiceProviders.PriorityAccessor<T> {}
+
+  public interface Supplier<T> {
+    T get();
+  }
 }

api/src/main/java/io/grpc/LoadBalancerRegistry.java

@@ -43,7 +43,6 @@
 public final class LoadBalancerRegistry {
   private static final Logger logger = Logger.getLogger(LoadBalancerRegistry.class.getName());
   private static LoadBalancerRegistry instance;
-  private static final Iterable<Class<?>> HARDCODED_CLASSES = getHardCodedClasses();
 
   private final LinkedHashSet<LoadBalancerProvider> allProviders =
       new LinkedHashSet<>();
@@ -105,7 +104,7 @@ public static synchronized LoadBalancerRegistry getDefaultRegistry() {
           ServiceLoader
             .load(LoadBalancerProvider.class, LoadBalancerProvider.class.getClassLoader())
             .iterator(),
-          HARDCODED_CLASSES,
+          LoadBalancerRegistry::getHardCodedClasses,
           new LoadBalancerPriorityAccessor());
       instance = new LoadBalancerRegistry();
       for (LoadBalancerProvider provider : providerList) {

api/src/main/java/io/grpc/ManagedChannelRegistry.java

@@ -104,7 +104,7 @@ public static synchronized ManagedChannelRegistry getDefaultRegistry() {
           ServiceLoader
             .load(ManagedChannelProvider.class, ManagedChannelProvider.class.getClassLoader())
             .iterator(),
-          getHardCodedClasses(),
+          ManagedChannelRegistry::getHardCodedClasses,
           new ManagedChannelPriorityAccessor());
       instance = new ManagedChannelRegistry();
       for (ManagedChannelProvider provider : providerList) {

api/src/main/java/io/grpc/NameResolverRegistry.java

@@ -129,7 +129,7 @@ public static synchronized NameResolverRegistry getDefaultRegistry() {
           ServiceLoader
             .load(NameResolverProvider.class, NameResolverProvider.class.getClassLoader())
             .iterator(),
-          getHardCodedClasses(),
+          NameResolverRegistry::getHardCodedClasses,
           new NameResolverPriorityAccessor());
       if (providerList.isEmpty()) {
         logger.warning("No NameResolverProviders found via ServiceLoader, including for DNS. This "

api/src/main/java/io/grpc/ServerRegistry.java

@@ -96,7 +96,7 @@ public static synchronized ServerRegistry getDefaultRegistry() {
           ServerProvider.class,
           ServiceLoader.load(ServerProvider.class, ServerProvider.class.getClassLoader())
             .iterator(),
-          getHardCodedClasses(),
+          ServerRegistry::getHardCodedClasses,
           new ServerPriorityAccessor());
       instance = new ServerRegistry();
       for (ServerProvider provider : providerList) {

api/src/main/java/io/grpc/ServiceProviders.java

@@ -17,6 +17,7 @@
 package io.grpc;
 
 import com.google.common.annotations.VisibleForTesting;
+import com.google.common.base.Supplier;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.Comparator;
@@ -44,7 +45,7 @@ private ServiceProviders() {
   public static <T> List<T> loadAll(
       Class<T> klass,
       Iterator<T> serviceLoader,
-      Iterable<Class<?>> hardcoded,
+      Supplier<Iterable<Class<?>>> hardcoded,
       final PriorityAccessor<T> priorityAccessor) {
     Iterator<T> candidates;
     if (serviceLoader instanceof ListIterator) {
@@ -58,7 +59,7 @@ public static <T> List<T> loadAll(
       candidates = serviceLoader;
     } else if (isAndroid(klass.getClassLoader())) {
       // Avoid getResource() on Android, which must read from a zip which uses a lot of memory
-      candidates = getCandidatesViaHardCoded(klass, hardcoded).iterator();
+      candidates = getCandidatesViaHardCoded(klass, hardcoded.get()).iterator();
     } else if (!serviceLoader.hasNext()) {
       // Attempt to load using the context class loader and ServiceLoader.
       // This allows frameworks like http://aries.apache.org/modules/spi-fly.html to plug in.

api/src/test/java/io/grpc/ServiceProvidersTest.java

@@ -16,28 +16,30 @@
 
 package io.grpc;
 
+import static com.google.common.truth.Truth.assertThat;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertNull;
 import static org.junit.Assert.assertSame;
 import static org.junit.Assert.assertTrue;
 import static org.junit.Assert.fail;
 
+import com.google.common.base.Supplier;
 import com.google.common.collect.ImmutableList;
 import io.grpc.InternalServiceProviders.PriorityAccessor;
 import java.util.Collections;
 import java.util.Iterator;
 import java.util.List;
 import java.util.ServiceConfigurationError;
 import java.util.ServiceLoader;
+import org.junit.After;
 import org.junit.Test;
 import org.junit.runner.RunWith;
 import org.junit.runners.JUnit4;
 
 /** Unit tests for {@link ServiceProviders}. */
 @RunWith(JUnit4.class)
 public class ServiceProvidersTest {
-  private static final List<Class<?>> NO_HARDCODED = Collections.emptyList();
   private static final PriorityAccessor<ServiceProvidersTestAbstractProvider> ACCESSOR =
       new PriorityAccessor<ServiceProvidersTestAbstractProvider>() {
         @Override
@@ -52,6 +54,19 @@ public int getPriority(ServiceProvidersTestAbstractProvider provider) {
       };
   private final String serviceFile =
       "META-INF/services/io.grpc.ServiceProvidersTestAbstractProvider";
+  private boolean failingHardCodedAccessed;
+  private final Supplier<Iterable<Class<?>>> failingHardCoded = new Supplier<Iterable<Class<?>>>() {
+    @Override
+    public Iterable<Class<?>> get() {
+      failingHardCodedAccessed = true;
+      throw new AssertionError();
+    }
+  };
+
+  @After
+  public void tearDown() {
+    assertThat(failingHardCodedAccessed).isFalse();
+  }
 
   @Test
   public void contextClassLoaderProvider() {
@@ -70,7 +85,8 @@ public void contextClassLoaderProvider() {
       Thread.currentThread().setContextClassLoader(rcll);
       assertEquals(
           Available7Provider.class,
-          load(ServiceProvidersTestAbstractProvider.class, NO_HARDCODED, cl, ACCESSOR).getClass());
+          load(ServiceProvidersTestAbstractProvider.class, failingHardCoded, cl, ACCESSOR)
+            .getClass());
     } finally {
       Thread.currentThread().setContextClassLoader(ccl);
     }
@@ -85,7 +101,7 @@ public void noProvider() {
           serviceFile,
           "io/grpc/ServiceProvidersTestAbstractProvider-doesNotExist.txt");
       Thread.currentThread().setContextClassLoader(cl);
-      assertNull(load(ServiceProvidersTestAbstractProvider.class, NO_HARDCODED, cl, ACCESSOR));
+      assertNull(load(ServiceProvidersTestAbstractProvider.class, failingHardCoded, cl, ACCESSOR));
     } finally {
       Thread.currentThread().setContextClassLoader(ccl);
     }
@@ -97,10 +113,11 @@ public void multipleProvider() throws Exception {
         "io/grpc/ServiceProvidersTestAbstractProvider-multipleProvider.txt");
     assertSame(
         Available7Provider.class,
-        load(ServiceProvidersTestAbstractProvider.class, NO_HARDCODED, cl, ACCESSOR).getClass());
+        load(ServiceProvidersTestAbstractProvider.class, failingHardCoded, cl, ACCESSOR)
+          .getClass());
 
     List<ServiceProvidersTestAbstractProvider> providers = loadAll(
-        ServiceProvidersTestAbstractProvider.class, NO_HARDCODED, cl, ACCESSOR);
+        ServiceProvidersTestAbstractProvider.class, failingHardCoded, cl, ACCESSOR);
     assertEquals(3, providers.size());
     assertEquals(Available7Provider.class, providers.get(0).getClass());
     assertEquals(Available5Provider.class, providers.get(1).getClass());
@@ -114,15 +131,16 @@ public void unavailableProvider() {
         "io/grpc/ServiceProvidersTestAbstractProvider-unavailableProvider.txt");
     assertEquals(
         Available7Provider.class,
-        load(ServiceProvidersTestAbstractProvider.class, NO_HARDCODED, cl, ACCESSOR).getClass());
+        load(ServiceProvidersTestAbstractProvider.class, failingHardCoded, cl, ACCESSOR)
+          .getClass());
   }
 
   @Test
   public void unknownClassProvider() {
     ClassLoader cl = new ReplacingClassLoader(getClass().getClassLoader(), serviceFile,
         "io/grpc/ServiceProvidersTestAbstractProvider-unknownClassProvider.txt");
     try {
-      loadAll(ServiceProvidersTestAbstractProvider.class, NO_HARDCODED, cl, ACCESSOR);
+      loadAll(ServiceProvidersTestAbstractProvider.class, failingHardCoded, cl, ACCESSOR);
       fail("Exception expected");
     } catch (ServiceConfigurationError e) {
       // noop
@@ -136,7 +154,7 @@ public void exceptionSurfacedToCaller_failAtInit() {
     try {
       // Even though there is a working provider, if any providers fail then we should fail
       // completely to avoid returning something unexpected.
-      loadAll(ServiceProvidersTestAbstractProvider.class, NO_HARDCODED, cl, ACCESSOR);
+      loadAll(ServiceProvidersTestAbstractProvider.class, failingHardCoded, cl, ACCESSOR);
       fail("Expected exception");
     } catch (ServiceConfigurationError expected) {
       // noop
@@ -149,7 +167,7 @@ public void exceptionSurfacedToCaller_failAtPriority() {
         "io/grpc/ServiceProvidersTestAbstractProvider-failAtPriorityProvider.txt");
     try {
       // The exception should be surfaced to the caller
-      loadAll(ServiceProvidersTestAbstractProvider.class, NO_HARDCODED, cl, ACCESSOR);
+      loadAll(ServiceProvidersTestAbstractProvider.class, failingHardCoded, cl, ACCESSOR);
       fail("Expected exception");
     } catch (FailAtPriorityProvider.PriorityException expected) {
       // noop
@@ -162,7 +180,7 @@ public void exceptionSurfacedToCaller_failAtAvailable() {
         "io/grpc/ServiceProvidersTestAbstractProvider-failAtAvailableProvider.txt");
     try {
       // The exception should be surfaced to the caller
-      loadAll(ServiceProvidersTestAbstractProvider.class, NO_HARDCODED, cl, ACCESSOR);
+      loadAll(ServiceProvidersTestAbstractProvider.class, failingHardCoded, cl, ACCESSOR);
       fail("Expected exception");
     } catch (FailAtAvailableProvider.AvailableException expected) {
       // noop
@@ -239,10 +257,10 @@ class RandomClass {}
 
   private static <T> T load(
       Class<T> klass,
-      Iterable<Class<?>> hardcoded,
+      Supplier<Iterable<Class<?>>> hardCoded,
       ClassLoader cl,
       PriorityAccessor<T> priorityAccessor) {
-    List<T> candidates = loadAll(klass, hardcoded, cl, priorityAccessor);
+    List<T> candidates = loadAll(klass, hardCoded, cl, priorityAccessor);
     if (candidates.isEmpty()) {
       return null;
     }
@@ -251,13 +269,13 @@ private static <T> T load(
 
   private static <T> List<T> loadAll(
       Class<T> klass,
-      Iterable<Class<?>> hardcoded,
+      Supplier<Iterable<Class<?>>> hardCoded,
       ClassLoader classLoader,
       PriorityAccessor<T> priorityAccessor) {
     return ServiceProviders.loadAll(
         klass,
         ServiceLoader.load(klass, classLoader).iterator(),
-        hardcoded,
+        hardCoded,
         priorityAccessor);
   }
 

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

@@ -113,7 +113,7 @@ public static synchronized XdsCredentialsRegistry getDefaultRegistry() {
               ServiceLoader
                 .load(XdsCredentialsProvider.class, XdsCredentialsProvider.class.getClassLoader())
                 .iterator(),
-              getHardCodedClasses(),
+              XdsCredentialsRegistry::getHardCodedClasses,
               new XdsCredentialsProviderPriorityAccessor());
       if (providerList.isEmpty()) {
         logger.warning("No XdsCredsRegistry found via ServiceLoader, including for GoogleDefault, "