feat(bigquery): make BigQuery AutoCloseable with default no-op close method

java-bigquery/google-cloud-bigquery/src/main/java/com/google/cloud/bigquery/BigQuery.java

@@ -40,7 +40,7 @@
  *
  * @see <a href="https://cloud.google.com/bigquery/what-is-bigquery">Google Cloud BigQuery</a>
  */
-public interface BigQuery extends Service<BigQueryOptions> {
+public interface BigQuery extends Service<BigQueryOptions>, AutoCloseable {
 
   /**
    * Fields of a BigQuery Dataset resource.
@@ -1821,4 +1821,14 @@ Object queryWithTimeout(
    * represents the subset of granted permissions.
    */
   List<String> testIamPermissions(TableId table, List<String> permissions, IAMOption... options);
+
+  /**
+   * Closes any background resources and transport channels held by this service.
+   *
+   * <p>The default implementation does nothing. Implementations that manage background resources
+   * (such as gRPC channels or storage clients) should override this method to release them
+   * deterministically.
+   */
+  @Override
+  default void close() {}
 }

java-bigquery/google-cloud-bigquery/src/main/java/com/google/cloud/bigquery/BigQueryImpl.java

@@ -504,6 +504,7 @@ private void closeClient() {
 
   private transient ConcurrentHashMap<String, BigQueryReadClient> bqReadClients;
   private transient boolean isGlobalClientUserProvided;
+  private transient volatile boolean closed = false;
 
   /**
    * Lazily creates or retrieves the shared {@link BigQueryReadClient} instance used for streaming
@@ -527,6 +528,9 @@ BigQueryReadClient getBigQueryReadClient() {
    * @throws BigQueryException if initializing the storage read client fails
    */
   BigQueryReadClient getBigQueryReadClient(String location) {
+    if (closed) {
+      throw new IllegalStateException("BigQuery service has been closed");
+    }
     String cacheKey = location != null ? location.toLowerCase() : "global";
     if (bqReadClients == null) {
       synchronized (this) {
@@ -543,6 +547,9 @@ BigQueryReadClient getBigQueryReadClient(String location) {
       return client;
     }
     synchronized (this) {
+      if (closed) {
+        throw new IllegalStateException("BigQuery service has been closed");
+      }
       client = bqReadClients.get(cacheKey);
       if (client == null && isGlobalClientUserProvided) {
         client = bqReadClients.get("global");
@@ -552,6 +559,10 @@ BigQueryReadClient getBigQueryReadClient(String location) {
         configureReadSettings(settingsBuilder, getOptions());
         try {
           client = BigQueryReadClient.create(settingsBuilder.build());
+          if (closed) {
+            client.close();
+            throw new IllegalStateException("BigQuery service has been closed");
+          }
           if (bqReadClients.size() < MAX_CACHED_READ_CLIENTS) {
             bqReadClients.put(cacheKey, client);
           }
@@ -583,6 +594,30 @@ void setBigQueryReadClient(String location, BigQueryReadClient client) {
     }
   }
 
+  /**
+   * Closes any background resources and transport channels held by this {@link BigQueryImpl},
+   * including the underlying {@link BigQueryReadClient} instances used for Arrow query streaming.
+   */
+  @Override
+  public void close() {
+    synchronized (this) {
+      if (closed) {
+        return;
+      }
+      closed = true;
+    }
+    if (bqReadClients != null) {
+      for (BigQueryReadClient client : bqReadClients.values()) {
+        try {
+          client.close();
+        } catch (Exception e) {
+          // Ignore exceptions during teardown
+        }
+      }
+      bqReadClients.clear();
+    }
+  }
+
   /**
    * Configures a {@link BigQueryReadSettings.Builder} with credentials, header provider, and
    * universe domain mapped from the given {@link BigQueryOptions}.

java-bigquery/google-cloud-bigquery/src/test/java/com/google/cloud/bigquery/BigQueryImplTest.java

@@ -4260,4 +4260,70 @@ void testTestIamPermissionsWhenNoPermissionsGranted() throws IOException {
         .testIamPermissionsSkipExceptionTranslation(
             resourceId, checkedPermissions, EMPTY_RPC_OPTIONS);
   }
+
+  @Test
+  void testCloseClosesBigQueryReadClient() {
+    BigQueryReadClient mockReadClient =
+        mock(BigQueryReadClient.class, withSettings().withoutAnnotations());
+    bigquery = options.getService();
+    ((BigQueryImpl) bigquery).setBigQueryReadClient(mockReadClient);
+
+    bigquery.close();
+
+    verify(mockReadClient, times(1)).close();
+  }
+
+  @Test
+  void testCloseIsIdempotent() {
+    BigQueryReadClient mockReadClient =
+        mock(BigQueryReadClient.class, withSettings().withoutAnnotations());
+    bigquery = options.getService();
+    ((BigQueryImpl) bigquery).setBigQueryReadClient(mockReadClient);
+
+    bigquery.close();
+    bigquery.close();
+
+    verify(mockReadClient, times(1)).close();
+  }
+
+  @Test
+  void testCloseWithoutReadClientDoesNotThrow() {
+    bigquery = options.getService();
+    bigquery.close();
+  }
+
+  @Test
+  void testTryWithResources() {
+    BigQueryReadClient mockReadClient =
+        mock(BigQueryReadClient.class, withSettings().withoutAnnotations());
+    try (BigQuery bq = options.getService()) {
+      ((BigQueryImpl) bq).setBigQueryReadClient(mockReadClient);
+      assertNotNull(bq);
+    }
+    verify(mockReadClient, times(1)).close();
+  }
+
+  @Test
+  void testGetBigQueryReadClientAfterCloseThrows() {
+    bigquery = options.getService();
+    bigquery.close();
+    assertThrows(
+        IllegalStateException.class, () -> ((BigQueryImpl) bigquery).getBigQueryReadClient());
+  }
+
+  @Test
+  void testCloseClosesAllRegionalBigQueryReadClients() {
+    BigQueryReadClient mockReadClientUs =
+        mock(BigQueryReadClient.class, withSettings().withoutAnnotations());
+    BigQueryReadClient mockReadClientEu =
+        mock(BigQueryReadClient.class, withSettings().withoutAnnotations());
+    bigquery = options.getService();
+    ((BigQueryImpl) bigquery).setBigQueryReadClient("us", mockReadClientUs);
+    ((BigQueryImpl) bigquery).setBigQueryReadClient("eu", mockReadClientEu);
+
+    bigquery.close();
+
+    verify(mockReadClientUs, times(1)).close();
+    verify(mockReadClientEu, times(1)).close();
+  }
 }