TaskQueue.java

/*
 * Copyright 2014, Stratio.
 *
 * Licensed 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 com.stratio.cassandra.util;

import com.stratio.cassandra.contrib.NotifyingBlockingThreadPoolExecutor;

import java.util.concurrent.ExecutionException;
import java.util.concurrent.Future;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.ReadWriteLock;
import java.util.concurrent.locks.ReentrantReadWriteLock;

/**
 * A queue that executes each submitted task using one of possibly several pooled threads. Tasks can be submitted with
 * an identifier, ensuring that all tasks with same identifier will be executed orderly in the same thread. Each thread
 * has its own task queue.
 *
 * @author Andres de la Pena <adelapena@stratio.com>
 */
public class TaskQueue {

    private NotifyingBlockingThreadPoolExecutor[] pools;

    private ReadWriteLock lock = new ReentrantReadWriteLock();

    /**
     * Returns a new {@link TaskQueue}
     *
     * @param numThreads The number of executor threads.
     * @param queuesSize The max number of tasks in each thread queue before blocking.
     */
    public TaskQueue(int numThreads, int queuesSize) {

        pools = new NotifyingBlockingThreadPoolExecutor[numThreads];
        for (int i = 0; i < numThreads; i++) {
            pools[i] = new NotifyingBlockingThreadPoolExecutor(1,
                                                               queuesSize,
                                                               Long.MAX_VALUE,
                                                               TimeUnit.DAYS,
                                                               0,
                                                               TimeUnit.NANOSECONDS,
                                                               null);
            pools[i].submit(new Runnable() {
                @Override
                public void run() {
                    Log.debug("Task queue starts");
                }
            });
        }
    }

    /**
     * Submits a non value-returning task for asynchronous execution.
     * <p/>
     * The specified identifier is used to choose the thread executor where the task will be queued. The selection and
     * load balancing is based in the {@link #hashCode()} of this identifier.
     *
     * @param id   The identifier of the task used to choose the thread executor where the task will be queued for
     *             asynchronous execution.
     * @param task A task to be queued for asynchronous execution.
     */
    public Future<?> submitAsynchronous(Object id, Runnable task) {
        lock.readLock().lock();
        try {
            int i = Math.abs(id.hashCode() % pools.length);
            return pools[i].submit(task);
        } catch (Exception e) {
            Log.error(e, "Task queue submission failed");
            throw new RuntimeException(e);
        } finally {
            lock.readLock().unlock();
        }
    }

    private void awaitInner() throws ExecutionException, InterruptedException {
        Future<?>[] futures = new Future<?>[pools.length];
        for (int i = 0; i < pools.length; i++) {
            Future<?> future = pools[i].submit(new Runnable() {
                @Override
                public void run() {
                }
            });
            futures[i] = future;
        }
        for (Future<?> future : futures) {
            future.get();
        }
    }

    public void await() {
        lock.writeLock().lock();
        try {
            awaitInner();
        } catch (InterruptedException e) {
            Log.error(e, "Await interrupted");
            throw new RuntimeException(e);
        } catch (ExecutionException e) {
            Log.error(e, "Await failed");
            throw new RuntimeException(e);
        } finally {
            lock.writeLock().unlock();
        }
    }

    /**
     * Submits a non value-returning task for synchronous execution. It waits for all synchronous tasks to be
     * completed.
     *
     * @param task A task to be executed synchronously.
     */
    public void submitSynchronous(Runnable task) {
        lock.writeLock().lock();
        try {
            awaitInner();
            task.run();
        } catch (InterruptedException e) {
            Log.error(e, "Task queue isolated submission interrupted");
            throw new RuntimeException(e);
        } catch (Exception e) {
            Log.error(e, "Task queue isolated submission failed");
            throw new RuntimeException(e);
        } finally {
            lock.writeLock().unlock();
        }
    }

}