Add new classes for eliminating xds config tears (#11740)

* Framework definition to support A74

xds/build.gradle

@@ -46,6 +46,7 @@ dependencies {
     thirdpartyImplementation project(':grpc-protobuf'),
             project(':grpc-stub')
     compileOnly sourceSets.thirdparty.output
+    testCompileOnly sourceSets.thirdparty.output
     implementation project(':grpc-stub'),
             project(':grpc-core'),
             project(':grpc-util'),
@@ -59,6 +60,7 @@ dependencies {
             libraries.protobuf.java.util
     def nettyDependency = implementation project(':grpc-netty')
 
+    testImplementation project(':grpc-api')
     testImplementation project(':grpc-rls')
     testImplementation project(':grpc-inprocess')
     testImplementation testFixtures(project(':grpc-core')),

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

@@ -0,0 +1,192 @@
+/*
+ * Copyright 2024 The gRPC Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.grpc.xds;
+
+import static com.google.common.base.Preconditions.checkNotNull;
+
+import com.google.common.collect.ImmutableMap;
+import io.grpc.StatusOr;
+import io.grpc.xds.XdsClusterResource.CdsUpdate;
+import io.grpc.xds.XdsEndpointResource.EdsUpdate;
+import io.grpc.xds.XdsListenerResource.LdsUpdate;
+import io.grpc.xds.XdsRouteConfigureResource.RdsUpdate;
+import java.io.Closeable;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Objects;
+
+/**
+ * Represents the xDS configuration tree for a specified Listener.
+ */
+final class XdsConfig {
+  private final LdsUpdate listener;
+  private final RdsUpdate route;
+  private final VirtualHost virtualHost;
+  private final ImmutableMap<String, StatusOr<XdsClusterConfig>> clusters;
+  private final int hashCode;
+
+  XdsConfig(LdsUpdate listener, RdsUpdate route, Map<String, StatusOr<XdsClusterConfig>> clusters,
+            VirtualHost virtualHost) {
+    this(listener, route, virtualHost, ImmutableMap.copyOf(clusters));
+  }
+
+  public XdsConfig(LdsUpdate listener, RdsUpdate route, VirtualHost virtualHost,
+                   ImmutableMap<String, StatusOr<XdsClusterConfig>> clusters) {
+    this.listener = listener;
+    this.route = route;
+    this.virtualHost = virtualHost;
+    this.clusters = clusters;
+
+    hashCode = Objects.hash(listener, route, virtualHost, clusters);
+  }
+
+  @Override
+  public boolean equals(Object obj) {
+    if (!(obj instanceof XdsConfig)) {
+      return false;
+    }
+
+    XdsConfig o = (XdsConfig) obj;
+
+    return hashCode() == o.hashCode() && Objects.equals(listener, o.listener)
+        && Objects.equals(route, o.route) && Objects.equals(virtualHost, o.virtualHost)
+        && Objects.equals(clusters, o.clusters);
+  }
+
+  @Override
+  public int hashCode() {
+    return hashCode;
+  }
+
+  @Override
+  public String toString() {
+    StringBuilder builder = new StringBuilder();
+    builder.append("XdsConfig{")
+        .append("\n  listener=").append(listener)
+        .append(",\n  route=").append(route)
+        .append(",\n  virtualHost=").append(virtualHost)
+        .append(",\n  clusters=").append(clusters)
+        .append("\n}");
+    return builder.toString();
+  }
+
+  public LdsUpdate getListener() {
+    return listener;
+  }
+
+  public RdsUpdate getRoute() {
+    return route;
+  }
+
+  public VirtualHost getVirtualHost() {
+    return virtualHost;
+  }
+
+  public ImmutableMap<String, StatusOr<XdsClusterConfig>> getClusters() {
+    return clusters;
+  }
+
+  static final class XdsClusterConfig {
+    private final String clusterName;
+    private final CdsUpdate clusterResource;
+    private final StatusOr<EdsUpdate> endpoint; //Will be null for non-EDS clusters
+
+    XdsClusterConfig(String clusterName, CdsUpdate clusterResource,
+                      StatusOr<EdsUpdate> endpoint) {
+      this.clusterName = checkNotNull(clusterName, "clusterName");
+      this.clusterResource = checkNotNull(clusterResource, "clusterResource");
+      this.endpoint = endpoint;
+    }
+
+    @Override
+    public int hashCode() {
+      int endpointHash = (endpoint != null) ? endpoint.hashCode() : 0;
+      return clusterName.hashCode() + clusterResource.hashCode() + endpointHash;
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+      if (!(obj instanceof XdsClusterConfig)) {
+        return false;
+      }
+      XdsClusterConfig o = (XdsClusterConfig) obj;
+      return Objects.equals(clusterName, o.clusterName)
+          && Objects.equals(clusterResource, o.clusterResource)
+          && Objects.equals(endpoint, o.endpoint);
+    }
+
+    @Override
+    public String toString() {
+      StringBuilder builder = new StringBuilder();
+      builder.append("XdsClusterConfig{clusterName=").append(clusterName)
+          .append(", clusterResource=").append(clusterResource)
+          .append(", endpoint=").append(endpoint).append("}");
+      return builder.toString();
+    }
+
+    public String getClusterName() {
+      return clusterName;
+    }
+
+    public CdsUpdate getClusterResource() {
+      return clusterResource;
+    }
+
+    public StatusOr<EdsUpdate> getEndpoint() {
+      return endpoint;
+    }
+  }
+
+  static final class XdsConfigBuilder {
+    private LdsUpdate listener;
+    private RdsUpdate route;
+    private Map<String, StatusOr<XdsClusterConfig>> clusters = new HashMap<>();
+    private VirtualHost virtualHost;
+
+    XdsConfigBuilder setListener(LdsUpdate listener) {
+      this.listener = checkNotNull(listener, "listener");
+      return this;
+    }
+
+    XdsConfigBuilder setRoute(RdsUpdate route) {
+      this.route = checkNotNull(route, "route");
+      return this;
+    }
+
+    XdsConfigBuilder addCluster(String name, StatusOr<XdsClusterConfig> clusterConfig) {
+      checkNotNull(name, "name");
+      checkNotNull(clusterConfig, "clusterConfig");
+      clusters.put(name, clusterConfig);
+      return this;
+    }
+
+    XdsConfigBuilder setVirtualHost(VirtualHost virtualHost) {
+      this.virtualHost = checkNotNull(virtualHost, "virtualHost");
+      return this;
+    }
+
+    XdsConfig build() {
+      checkNotNull(listener, "listener");
+      checkNotNull(route, "route");
+      return new XdsConfig(listener, route, clusters, virtualHost);
+    }
+  }
+
+  public interface XdsClusterSubscriptionRegistry {
+    Closeable subscribeToCluster(String clusterName);
+  }
+}