feat(bigtable): update legacy escape hatch to return V2 admin clients (googleapis#13375)

This PR updates the legacy `BigtableTableAdminClient` and
`BigtableInstanceAdminClient` escape hatches (`getBaseClient()`) to
return the modern V2 admin clients (`BigtableTableAdminClientV2` and
`BigtableInstanceAdminClientV2`) instead of the autogenerated base
clients (`BaseBigtableTableAdminClient` and
`BaseBigtableInstanceAdminClient`).

Author: jinseopkim0

java-bigtable/google-cloud-bigtable/src/main/java/com/google/cloud/bigtable/admin/v2/BigtableInstanceAdminClient.java

@@ -125,7 +125,7 @@
 public final class BigtableInstanceAdminClient implements AutoCloseable {
   private final String projectId;
   private final BigtableInstanceAdminStub stub;
-  private final BaseBigtableInstanceAdminClient baseClient;
+  private final BigtableInstanceAdminClientV2 v2Client;
 
   /** Constructs an instance of BigtableInstanceAdminClient with the given project ID. */
   public static BigtableInstanceAdminClient create(@Nonnull String projectId) throws IOException {
@@ -148,7 +148,7 @@ private BigtableInstanceAdminClient(
       @Nonnull String projectId, @Nonnull BigtableInstanceAdminStub stub) {
     this.projectId = projectId;
     this.stub = stub;
-    this.baseClient = BaseBigtableInstanceAdminClient.create(stub);
+    this.v2Client = new BigtableInstanceAdminClientV2(stub);
   }
 
   /** Gets the project ID this client is associated with. */
@@ -157,11 +157,11 @@ public String getProjectId() {
   }
 
   /**
-   * Returns the modern autogenerated client. This provides access to the newest features and
-   * proto-based methods.
+   * Returns the modern V2 client. This provides access to the newest features and proto-based
+   * methods.
    */
-  public BaseBigtableInstanceAdminClient getBaseClient() {
-    return baseClient;
+  public BigtableInstanceAdminClientV2 getBaseClient() {
+    return v2Client;
   }
 
   /** Closes the client and frees all resources associated with it (like thread pools). */

java-bigtable/google-cloud-bigtable/src/main/java/com/google/cloud/bigtable/admin/v2/BigtableTableAdminClient.java

@@ -89,6 +89,7 @@
 import java.util.List;
 import java.util.Map;
 import java.util.concurrent.ExecutionException;
+import java.util.concurrent.ScheduledExecutorService;
 import javax.annotation.Nonnull;
 
 /**
@@ -169,7 +170,7 @@ public final class BigtableTableAdminClient implements AutoCloseable {
   private final EnhancedBigtableTableAdminStub stub;
   private final String projectId;
   private final String instanceId;
-  private final BaseBigtableTableAdminClient baseClient;
+  private BigtableTableAdminClientV2 v2Client;
 
   /** Constructs an instance of BigtableTableAdminClient with the given project and instance IDs. */
   public static BigtableTableAdminClient create(
@@ -209,7 +210,6 @@ private BigtableTableAdminClient(
     this.projectId = projectId;
     this.instanceId = instanceId;
     this.stub = stub;
-    this.baseClient = BaseBigtableTableAdminClient.create(stub);
   }
 
   /** Gets the project ID of the instance whose tables this client manages. */
@@ -223,11 +223,29 @@ public String getInstanceId() {
   }
 
   /**
-   * Returns the modern autogenerated client. This provides access to the newest features and
-   * proto-based methods.
-   */
-  public BaseBigtableTableAdminClient getBaseClient() {
-    return baseClient;
+   * Returns the modern V2 client. This provides access to the newest features and proto-based
+   * methods.
+   */
+  public synchronized BigtableTableAdminClientV2 getBaseClient() {
+    if (v2Client == null) {
+      ScheduledExecutorService backgroundExecutor =
+          stub.getSettings().getBackgroundExecutorProvider().getExecutor();
+      boolean shouldAutoClose =
+          stub.getSettings().getBackgroundExecutorProvider().shouldAutoClose();
+
+      try {
+        v2Client =
+            BigtableTableAdminClientV2.create(
+                stub,
+                stub.getSettings(),
+                stub.getClientContext().getClock(),
+                backgroundExecutor,
+                shouldAutoClose);
+      } catch (IOException e) {
+        throw new IllegalStateException("Failed to initialize modern V2 table admin client", e);
+      }
+    }
+    return v2Client;
   }
 
   @Override

java-bigtable/google-cloud-bigtable/src/main/java/com/google/cloud/bigtable/admin/v2/BigtableTableAdminClientV2.java

@@ -108,7 +108,8 @@ public static final BigtableTableAdminClientV2 create(BaseBigtableTableAdminSett
 
     OperationCallable<Void, Empty, OptimizeRestoredTableMetadata>
         optimizeRestoredTableOperationBaseCallable =
-            createOptimizeRestoredTableOperationBaseCallable(stub, settings, backgroundExecutor);
+            createOptimizeRestoredTableOperationBaseCallable(
+                stub, settings.getStubSettings().getClock(), backgroundExecutor);
 
     return new BigtableTableAdminClientV2(
         stub,
@@ -118,6 +119,34 @@ public static final BigtableTableAdminClientV2 create(BaseBigtableTableAdminSett
         optimizeRestoredTableOperationBaseCallable);
   }
 
+  /**
+   * Package-private factory method to construct an instance of {@link BigtableTableAdminClientV2}
+   * by reusing an existing stub, settings, clock, and background executor.
+   *
+   * <p>This is used by the legacy {@code BigtableTableAdminClient}'s escape hatch ({@code
+   * getBaseClient()}) to wrap the legacy client's active stub, ensuring the underlying gRPC channel
+   * and resources are shared rather than recreated.
+   */
+  static BigtableTableAdminClientV2 create(
+      GrpcBigtableTableAdminStub stub,
+      BigtableTableAdminStubSettings settings,
+      ApiClock clock,
+      ScheduledExecutorService backgroundExecutor,
+      boolean shouldAutoClose)
+      throws IOException {
+    AwaitConsistencyCallableV2 awaitConsistencyCallable =
+        createAwaitConsistencyCallable(stub, settings, clock, backgroundExecutor);
+    OperationCallable<Void, Empty, OptimizeRestoredTableMetadata>
+        optimizeRestoredTableOperationBaseCallable =
+            createOptimizeRestoredTableOperationBaseCallable(stub, clock, backgroundExecutor);
+    return new BigtableTableAdminClientV2(
+        stub,
+        backgroundExecutor,
+        shouldAutoClose,
+        awaitConsistencyCallable,
+        optimizeRestoredTableOperationBaseCallable);
+  }
+
   protected BigtableTableAdminClientV2(
       GrpcBigtableTableAdminStub stub,
       @Nullable ScheduledExecutorService backgroundExecutor,
@@ -156,7 +185,7 @@ private static AwaitConsistencyCallableV2 createAwaitConsistencyCallable(
   private static OperationCallable<Void, Empty, OptimizeRestoredTableMetadata>
       createOptimizeRestoredTableOperationBaseCallable(
           GrpcBigtableTableAdminStub stub,
-          BaseBigtableTableAdminSettings settings,
+          ApiClock clock,
           ScheduledExecutorService backgroundExecutor)
           throws IOException {
 
@@ -229,7 +258,7 @@ public Empty apply(OperationSnapshot input) {
     // (including channels, credentials, and headers) for executing the polling RPCs.
     ClientContext clientContext =
         ClientContext.newBuilder()
-            .setClock(settings.getStubSettings().getClock())
+            .setClock(clock)
             .setExecutor(backgroundExecutor)
             .setDefaultCallContext(GrpcCallContext.createDefault())
             .build();

java-bigtable/google-cloud-bigtable/src/main/java/com/google/cloud/bigtable/admin/v2/stub/EnhancedBigtableTableAdminStub.java

@@ -245,4 +245,12 @@ public UnaryCallable<ConsistencyRequest, Void> awaitConsistencyCallable() {
       awaitOptimizeRestoredTableCallable() {
     return optimizeRestoredTableOperationBaseCallable;
   }
+
+  public BigtableTableAdminStubSettings getSettings() {
+    return settings;
+  }
+
+  public ClientContext getClientContext() {
+    return clientContext;
+  }
 }