ConcurrencyUtil.java

/**
 *  Copyright 2009, 2010 The Regents of the University of California
 *  Licensed under the Educational Community 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.osedu.org/licenses/ECL-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 ch.entwine.weblounge.bridge.oaipmh.util;

import org.opencastproject.util.data.Function0;

import java.util.concurrent.ExecutorService;
import java.util.concurrent.TimeUnit;

/**
 * Functions dealing with concurrency.
 */
public final class ConcurrencyUtil {

  private ConcurrencyUtil() {
  }

  /**
   * Gently shut down an executor service. Waits for <code>waitSeconds</code>
   * then tries to forcibly terminate the service. Waits again then calls
   * <code>executorDoesNotTerminate</code>.
   */
  public static void shutdownAndAwaitTermination(ExecutorService exe,
      int waitSeconds, Function0<Void> executorDoesNotTerminate) {
    // Disable new tasks from being submitted
    exe.shutdown();
    try {
      // Wait a while for existing tasks to terminate
      if (!exe.awaitTermination(waitSeconds, TimeUnit.SECONDS)) {
        // Cancel currently executing tasks
        exe.shutdownNow();
        // Wait a while for tasks to respond to being cancelled
        if (!exe.awaitTermination(waitSeconds, TimeUnit.SECONDS))
          executorDoesNotTerminate.apply();
      }
    } catch (InterruptedException ie) {
      // Forcibly terminate on interruption
      exe.shutdownNow();
      // Preserve interrupt status
      Thread.currentThread().interrupt();
    }
  }
}