Java线程池实现多消费者批量处理队列消息

通常生产者-消费者的经典实现方式是，启动一个消费者线程从阻塞队列里获取消息进行消费，(多个)生产者往队列里插入待消费的数据然后立即返回。如果生产者生产的速率远大于消费者消费的速率，那么队列的待处理数据就会累积得越来越多。

本文的重点是封装实现(单个)消费者线程可以“批量处理”队列里的消息，这类似于多条数据插入数据库，由多次insert优化为一次batch insert。

顾名思义，“多消费者”就是开启多个消费者线程（其中每个消费者线程均可以批量处理队列消息），这里借用Java线程池来管理线程的生命周期：

首先，定义一个接口表示异步消费：

import java.util.concurrent.RejectedExecutionException;

/**
 * An object that accepts elements for future consuming.
 *
 * @param <E> The type of element to be consumed
 */
public interface AsynchronousConsumer<E> {

	/**
     * Accept an element for future consuming.
     *
     * @param e the element to be consumed
     * @return true if accepted, false otherwise
     * @throws NullPointerException if the specified element is null
     * @throws IllegalArgumentException if some property of this element
     *         prevents it from being accepted for future consuming
     * @throws RejectedExecutionException if the element
     *         cannot be accepted for consuming
     */
	public boolean accept(E e);
}

再定义一个消费者线程（由于线程托管给线程池管理了，这里是定义一个Runnable），多个Runnable通过共用BlockingQueue来实现多个消费者消费。这里 通过指定“batchSize”来表示批量处理（如果值大于1的话），TimeUnit指明了线程(Runnable)的最大空闲时间，超过该时间将会自动退出（如果值为0则表示永远等待）并提供beforeConsume、afterConsume、terminated等方法以便扩展：

import java.util.ArrayList;
import java.util.List;
import java.util.Objects;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.RejectedExecutionException;
import java.util.concurrent.TimeUnit;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;


/**
 * An abstract {@code Runnable} of consumer for batches consuming Asynchronously
 *
 * @param <E> The type of element to be consumed
 */
public abstract class ConsumerRunnable<E> implements Runnable, AsynchronousConsumer<E>{
	
	/**
	 * for recording any exception
	 */
	private static final Log log = LogFactory.getLog(ConsumerRunnable.class);
	
	
	/**the elements queue**/
	private final BlockingQueue<E> queue;
	
	/**
	 * the batchSize for {@link #consume} used in every loop
	 */
	private volatile int batchSize;
	
	/**
     * Timeout in nanoseconds for polling an element from the
     * working queue(BlockingQueue).Thread uses this timeout to
     * wait up if the working queue is empty. 
     * zero means wait forever until an element become available.
     */
	private volatile long waitTime;
	
	/**
	 * If true then will cause run() quit
     * when waiting for element if interrupted
	 */
	private volatile boolean quitIfInterrupted = true;
	
	/**
	 * Allocates a new {@code ConsumerRunnable} object
	 * with the given initial parameters and default waitTime(0)
	 * which will cause the thread to wait forever until an element
	 * become available when the element queue is empty.
     * 
	 * @param queue the BlockingQueue for working
	 * @param batchSize the batch size used in {@link #consume} for every loop
	 * 
	 * @throws NullPointerException if the queue is null
	 * @throws IllegalArgumentException if the batchSize is less then or equal to zero
	 */
	public ConsumerRunnable(int batchSize, BlockingQueue<E> queue){
		this.batchSize = PracticalUtils.requirePositive(batchSize);
		this.queue = Objects.requireNonNull(queue);
	}
	
	/**
	 * Allocates a new {@code ConsumerRunnable} object
	 * with the given initial parameters.
	 * A time value of zero will cause the thread to wait forever
     * until an element become available when the element queue is empty.
     * 
	 * @param queue the BlockingQueue for working
	 * @param batchSize the batch size used in {@link #consume} for every loop
	 * @param time the time to wait. A time value of zero will cause
	 * the thread to wait forever until an element become available
	 * when the element queue is empty.
	 * @param unit the time unit of the time argument
	 * 
	 * @throws NullPointerException if any specified parameter is null
	 * @throws IllegalArgumentException if the batchSize is less then or equal to zero,
	 * or the time is less than zero
	 */
	public ConsumerRunnable(int batchSize, long time, TimeUnit unit,
			BlockingQueue<E> queue){
		this.batchSize = PracticalUtils.requirePositive(batchSize);
		this.queue = Objects.requireNonNull(queue);
		setWaitTime(time, unit);
	}
	
	
	/**
     * Accept an element for future consuming.
     * 
     * <p>Default implementation is equally invoke
     *  {@link java.util.Queue#offer queue.offer}
     *
     * @param e the element to be consumed
     * @throws NullPointerException if the specified element is null
     * @throws IllegalArgumentException if some property of this element
     *         prevents it from being accepted for future consuming
     * @throws RejectedExecutionException if the element
     *         cannot be accepted for future consuming (optional)
     * @return true if accepted, false otherwise
     */
	public boolean accept(E e){
		Objects.requireNonNull(e);
		return queue.offer(e);
	}
	
	
	/**
     * Main worker run loop.  Repeatedly gets elements from working queue
     * and consumes them, while coping with a number of issues:
     *
     * <p>1. Each loop run is preceded by a call to beforeConsume, which
     * might throw an exception, in which case the {@link #consume}
     * of the current loop will not be invoked.
     *
     * <p>2. Assuming beforeConsume completes normally, we consume the elements,
     * gathering any of its thrown exceptions to send to afterConsume. Any thrown
     * exception in the afterConsume conservatively causes the runnable to quit.
     *
     * <p>3. After {@link #consume} of the current loop completes, we call afterExecute,
     * which may also throw an exception, which will cause the runnable to quit.
     *
     */
	@Override
	public final void run() {
		starting();
		final List<E> list = new ArrayList<>();
		try{
			while(true){
				try {
					E info;
					int bSize = batchSize;
					for(int i=0;i<bSize&&list.size()<bSize&&(info=queue.poll())!=null;i++){
						list.add(info);
					}
					if(list.isEmpty()){
						try{
							beforeWait();
						} catch(Throwable ingnore){}
						//waiting if necessary until an element becomes available
						if(waitTime==0){
							list.add(queue.take());
						}else{
							E e = queue.poll(waitTime, TimeUnit.NANOSECONDS);
							if(e==null){//timeout
								break;
							}
							list.add(e);
						}
						
					}else{
						try{
							beforeConsume(list);
						}catch (Throwable t1) {
							list.clear();//clear to be reused for next loop
							log.error("The runnable["+getClass().getName()+"] which invoked beforeConsume occurred the exception:"
									+t1.toString(), t1);
							continue;
						}
						doConsume(list);
					}
				} catch (InterruptedException e) {
					if(quitIfInterrupted){
						Thread t = Thread.currentThread();
						if(!t.isInterrupted()){
							//restores the interrupted status
							t.interrupt();
						}
						break;
					}
				} catch(Throwable t){
					if(t instanceof Error){
						log.error("The runnable["+getClass().getName()+"] is about to die for the reason:"+t.toString(), t);
						break;
					}
					// else continue;
				}
			}
		} finally{
			try{
				//rechcek the list
				if(!list.isEmpty()){
					beforeConsume(list);
					doConsume(list);
				}
			} finally{
				terminated();
			}
		}
		
	}
	
	/**
	 * Consuming elements and ensure that the method
	 * {@code afterConsume} must be invoked in the end.
	 * @param list the elements that will be consumed
	 */
	private void doConsume(List<E> list){
		Throwable t = null;
		try {
			consume(list);
		} catch (Throwable t1) {
			t = t1;
			throw t1;
		} finally{
			try {
				afterConsume(list,t);
			} finally{
				list.clear();//clear to be reused for next loop
			}
		}
	}
	
	/**
	 * Returns the batchSize for {@link #consume} used in every loop
	 * 
	 * @return the batchSize
	 * 
	 * @see #setBatchSize
	 */
	public int getBatchSize(){
		return batchSize;
	}
	
	/**
     * Sets the batchSize for next loop used in {@link #consume}.
     * This overrides any value set in the constructor.
     *
     * @param batchSize the new batchSize
     * @throws IllegalArgumentException if the new batchSize is
     *         less than or equal to zero
     * @see #getBatchSize
     */
	public void setBatchSize(int batchSize){
		this.batchSize = PracticalUtils.requirePositive(batchSize);
	}
	
    
    /**
     * Returns the element queue used by this thread. Access to the
     * element queue is intended primarily for debugging and monitoring.
     * This queue may be in active use.  Retrieving the element queue
     * does not prevent queued element from being saved.
     *
     * @return the element queue
     */
    public BlockingQueue<E> getQueue() {
        return queue;
    }
    
    /**
     * Sets the time limit for the thread when waiting for
     * an element to become available. This overrides any value
     * set in the constructor. zero means wait forever.
     * Timeout will cause the runnable to quit.
     *
     * @param time the time to wait.  A time value of zero will cause
     *        the thread to wait forever until an element become available
     *        when the element queue is empty.
     * @param unit the time unit of the {@code time} argument
     * @throws IllegalArgumentException if {@code time} less than zero
     * @see #getWaitTime(TimeUnit)
     */
    public void setWaitTime(long time, TimeUnit unit) {
        long t = unit.toNanos(PracticalUtils.requireNonNegative(time));
        this.waitTime = t;
    }
    

    /**
     * Returns the thread waiting time, which is the time to wait up
     * when the working queue is  empty. zero means wait forever.
     *
     * @param unit the desired time unit of the result
     * @return the time limit
     * @see #setWaitTime(long, TimeUnit)
     */
    public long getWaitTime(TimeUnit unit) {
        return unit.convert(waitTime, TimeUnit.NANOSECONDS);
    }
    
    /**
     * Returns true if this runnable will quit
     * if interrupted when waiting for element.
     * @return true if this runnable will quit
     * if interrupted when waiting for element
     */
    public boolean isQuitIfInterrupted(){return quitIfInterrupted;}
    
    /**
     * Set quit or not if interrupted when waiting for element.
     * @param quitIfInterrupted true will cause run() quit
     * if interrupted when waiting for element
     */
    public void setQuitIfInterrupted(boolean quitIfInterrupted){
    	this.quitIfInterrupted = quitIfInterrupted;
    }
    
    
    /* Extension hooks */
    
    /**
     * Method invoked at the beginning of the run() method.
     * <p><b>Note:</b>if this method throw any exception then
     * any other method will not be invoked and cause the runnable to quit.
     */
    protected void starting() { }
    
    /**
     * Method invoked prior to current thread waiting for
     * an element to become available.
     * Any exception thrown by this method will be ignored.
     * 
     * <p>This implementation does nothing, but may be customized in
     * subclasses. Note: To properly nest multiple overridings, subclasses
     * should generally invoke {@code super.beforeWaiting} at the end of
     * this method.
     *
     */
    protected void beforeWait() { }

    /**
     * Method invoked prior to invoking {@link #consume} in the
     * current runnable for every loop.
     * 
     * <p><b>Note:</b>if this method throw any exception then the
     * {@link #consume} of current loop will not be invoked
     * 
     * <p>This implementation does nothing, but may be customized in
     * subclasses. Note: To properly nest multiple overridings, subclasses
     * should generally invoke {@code super.beforeConsume} at the end of
     * this method.
     *
     * @param list the elements that will be consumed
     */
    protected void beforeConsume(List<E> list) { }
    
    /**
	 * For subclass to implement the consume actions.
	 * 
	 * @param list the elements that will be consumed
	 */
	protected abstract void consume(List<E> list);
	
    /**
     * Method invoked upon one loop completion of {@link #consume} invoked.
     * This method is invoked by the current thread. If
     * non-null, the Throwable is the uncaught {@code Error}
     * that caused execution to terminate abruptly.
     *
     * <p>This implementation does nothing, but may be customized in
     * subclasses. Note: To properly nest multiple overridings, subclasses
     * should generally invoke {@code super.afterConsume} at the
     * beginning of this method.
     *
     * @param list the elements that has consumed(or to be consumed if the exception caused termination)
     * @param t the exception that caused terminati