Throttling Task Submission with a BlockingExecutor http://www.javacodegeeks.com/2013/11/throttling-task-submission-with-a-blockingexecutor.html http://fahdshariff.blogspot.fr/2013/11/throttling-task-submission-with.html

gistfile1.java

import java.util.concurrent.LinkedBlockingQueue;
import java.util.concurrent.RejectedExecutionException;
import java.util.concurrent.Semaphore;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * An executor which blocks and prevents further tasks from
 * being submitted to the pool when the queue is full.
 * <p>
 * Based on the BoundedExecutor example in:
 * Brian Goetz, 2006. Java Concurrency in Practice. (Listing 8.4)
 */
public class BlockingExecutor extends ThreadPoolExecutor {

  private static final Logger LOGGER = LoggerFactory.
                                          getLogger(BlockingExecutor.class);
  private final Semaphore semaphore;

  /**
   * Creates a BlockingExecutor which will block and prevent further
   * submission to the pool when the specified queue size has been reached.
   *
   * @param poolSize the number of the threads in the pool
   * @param queueSize the size of the queue
   */
  public BlockingExecutor(final int poolSize, final int queueSize) {
    super(poolSize, poolSize, 0L, TimeUnit.MILLISECONDS,
          new LinkedBlockingQueue<Runnable>());

    // the semaphore is bounding both the number of tasks currently executing
    // and those queued up
    semaphore = new Semaphore(poolSize + queueSize);
  }

  /**
   * Executes the given task.
   * This method will block when the semaphore has no permits
   * i.e. when the queue has reached its capacity.
   */
  @Override
  public void execute(final Runnable task) {
    boolean acquired = false;
    do {
        try {
            semaphore.acquire();
            acquired = true;
        } catch (final InterruptedException e) {
            LOGGER.warn("InterruptedException whilst aquiring semaphore", e);
        }
    } while (!acquired);

    try {
        super.execute(task);
    } catch (final RejectedExecutionException e) {
        semaphore.release();
        throw e;
    }
  }

  /**
   * Method invoked upon completion of execution of the given Runnable,
   * by the thread that executed the task.
   * Releases a semaphore permit.
   */
  @Override
  protected void afterExecute(final Runnable r, final Throwable t) {
    super.afterExecute(r, t);
    semaphore.release();
  }
}