exec/java-exec/src/main/java/org/apache/drill/exec/testing/CountDownLatchInjection.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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 org.apache.drill.exec.testing;

import org.apache.drill.common.AutoCloseables.Closeable;

/**
 * This class is used internally for tracking injected countdown latches. These latches are specified via
 * {@link org.apache.drill.exec.ExecConstants#DRILLBIT_CONTROL_INJECTIONS} session option.
 *
 * This injection is useful in the case where a thread spawns multiple threads. The parent thread initializes the latch
 * with the expected number of countdown and awaits. The child threads count down on the same latch (same site class
 * and same descriptor), and once there are enough, the parent thread continues.
 */
public interface CountDownLatchInjection extends Closeable {

  /**
   * Initializes the underlying latch
   * @param count the number of times {@link #countDown} must be invoke before threads can pass through {@link #await}
   */
  void initialize(final int count);

  /**
   * Causes the current thread to wait until the latch has counted down to zero, unless the thread is
   * {@link Thread#interrupt interrupted}.
   */
  void await() throws InterruptedException;

  /**
   * Await without interruption. In the case of interruption, log a warning and continue to wait.
   */
  void awaitUninterruptibly();

  /**
   * Decrements the count of the latch, releasing all waiting threads if the count reaches zero.
   */
  void countDown();

  /**
   * Close the latch.
   */
  void close();
}