core: make service config error handling optional implementation (#6564)

Author: creamsoup

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

@@ -112,7 +112,11 @@ public abstract class LoadBalancer {
    * The load-balancing config converted from an JSON object injected by the GRPC library.
    *
    * <p>{@link NameResolver}s should not produce this attribute.
+   *
+   * <p>Deprecated: LB implementations should use parsed object from {@link
+   * LoadBalancerProvider#parseLoadBalancingPolicyConfig(Map)} instead of raw config.
    */
+  @Deprecated
   @NameResolver.ResolutionResultAttr
   public static final Attributes.Key<Map<String, ?>> ATTR_LOAD_BALANCING_CONFIG =
       Attributes.Key.create("io.grpc.LoadBalancer.loadBalancingConfig");

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

@@ -316,6 +316,7 @@ public abstract static class Listener2 implements Listener {
     @Deprecated
     public final void onAddresses(
         List<EquivalentAddressGroup> servers, @ResolutionResultAttr Attributes attributes) {
+      // TODO(jihuncho) need to promote Listener2 if we want to use ConfigOrError
       onResult(
           ResolutionResult.newBuilder().setAddresses(servers).setAttributes(attributes).build());
     }
@@ -330,8 +331,8 @@ public final void onAddresses(
     public abstract void onResult(ResolutionResult resolutionResult);
 
     /**
-     * Handles an error from the resolver. The listener is responsible for eventually invoking
-     * {@link NameResolver#refresh()} to re-attempt resolution.
+     * Handles a name resolving error from the resolver. The listener is responsible for eventually
+     * invoking {@link NameResolver#refresh()} to re-attempt resolution.
      *
      * @param error a non-OK status
      * @since 1.21.0
@@ -897,6 +898,23 @@ public Status getError() {
       return status;
     }
 
+    @Override
+    public boolean equals(Object o) {
+      if (this == o) {
+        return true;
+      }
+      if (o == null || getClass() != o.getClass()) {
+        return false;
+      }
+      ConfigOrError that = (ConfigOrError) o;
+      return Objects.equal(status, that.status) && Objects.equal(config, that.config);
+    }
+
+    @Override
+    public int hashCode() {
+      return Objects.hashCode(status, config);
+    }
+
     @Override
     public String toString() {
       if (config != null) {

core/src/main/java/io/grpc/internal/AbstractManagedChannelImplBuilder.java

@@ -93,6 +93,13 @@ public static ManagedChannelBuilder<?> forTarget(String target) {
   private static final long DEFAULT_RETRY_BUFFER_SIZE_IN_BYTES = 1L << 24;  // 16M
   private static final long DEFAULT_PER_RPC_BUFFER_LIMIT_IN_BYTES = 1L << 20; // 1M
 
+  @VisibleForTesting
+  static final String ENABLE_SERVICE_CONFIG_ERROR_HANDLING_PROPERTY =
+      "io.grpc.internal.ManagedChannelImpl.enableServiceConfigErrorHandling";
+  private static final boolean DEFAULT_ENABLE_SERVICE_CONFIG_ERROR_HANDLING =
+      Boolean.parseBoolean(
+          System.getProperty(ENABLE_SERVICE_CONFIG_ERROR_HANDLING_PROPERTY, "false"));
+
   ObjectPool<? extends Executor> executorPool = DEFAULT_EXECUTOR_POOL;
 
   ObjectPool<? extends Executor> offloadExecutorPool = DEFAULT_EXECUTOR_POOL;
@@ -152,6 +159,8 @@ public static ManagedChannelBuilder<?> forTarget(String target) {
   @Nullable
   ProxyDetector proxyDetector;
 
+  boolean enableServiceConfigErrorHandling = DEFAULT_ENABLE_SERVICE_CONFIG_ERROR_HANDLING;
+
   /**
    * Sets the maximum message size allowed for a single gRPC frame. If an inbound messages
    * larger than this limit is received it will not be processed and the RPC will fail with
@@ -454,6 +463,16 @@ public T disableServiceConfigLookUp() {
     return thisT();
   }
 
+  /**
+   * Enables service config error handling implemented in {@link ManagedChannelImpl2}. By default,
+   * it is disabled unless system property {@link #ENABLE_SERVICE_CONFIG_ERROR_HANDLING_PROPERTY} is
+   * set to {@code "true"}.
+   */
+  protected T enableServiceConfigErrorHandling() {
+    this.enableServiceConfigErrorHandling = true;
+    return thisT();
+  }
+
   /**
    * Disable or enable stats features. Enabled by default.
    *
@@ -514,6 +533,17 @@ protected String checkAuthority(String authority) {
 
   @Override
   public ManagedChannel build() {
+    if (this.enableServiceConfigErrorHandling) {
+      return new ManagedChannelOrphanWrapper(new ManagedChannelImpl2(
+          this,
+          buildTransportFactory(),
+          // TODO(carl-mastrangelo): Allow clients to pass this in
+          new ExponentialBackoffPolicy.Provider(),
+          SharedResourcePool.forResource(GrpcUtil.SHARED_CHANNEL_EXECUTOR),
+          GrpcUtil.STOPWATCH_SUPPLIER,
+          getEffectiveInterceptors(),
+          TimeProvider.SYSTEM_TIME_PROVIDER));
+    }
     return new ManagedChannelOrphanWrapper(new ManagedChannelImpl(
         this,
         buildTransportFactory(),

core/src/main/java/io/grpc/internal/AutoConfiguredLoadBalancerFactory.java

@@ -45,6 +45,7 @@
 import java.util.logging.Logger;
 import javax.annotation.Nullable;
 
+@SuppressWarnings("deprecation") // migrate to AutoConfiguredLoadBalancerFactory2 is required
 public final class AutoConfiguredLoadBalancerFactory {
   private static final Logger logger =
       Logger.getLogger(AutoConfiguredLoadBalancerFactory.class.getName());