public final class WorkProcessor<T>
    implements EventProcessor
{
    private final AtomicBoolean running = new AtomicBoolean(false); //当前处理器状态
    private final Sequence sequence = new Sequence(Sequencer.INITIAL_CURSOR_VALUE); //当前已消费过的最新序号
    private final RingBuffer<T> ringBuffer; //保留此引用，方便取数据
    private final SequenceBarrier sequenceBarrier; //用于等待下一个最大可用序号，可与多个Processor共用
    private final WorkHandler<? super T> workHandler; //实际上的处理器
    private final ExceptionHandler<? super T> exceptionHandler;
    private final Sequence workSequence; //多个Processor共用的workSequence，可以得到下一个待处理的序号

    private final EventReleaser eventReleaser = new EventReleaser()
    {
        @Override
        public void release()
        {
            sequence.set(Long.MAX_VALUE);
        }
    };

    private final TimeoutHandler timeoutHandler;

    /**
     * Construct a {@link WorkProcessor}.
     *
     * @param ringBuffer       to which events are published.
     * @param sequenceBarrier  on which it is waiting.
     * @param workHandler      is the delegate to which events are dispatched.
     * @param exceptionHandler to be called back when an error occurs
     * @param workSequence     from which to claim the next event to be worked on.  It should always be initialised
     *                         as {@link Sequencer#INITIAL_CURSOR_VALUE}
     */
    public WorkProcessor(
        final RingBuffer<T> ringBuffer,
        final SequenceBarrier sequenceBarrier,
        final WorkHandler<? super T> workHandler,
        final ExceptionHandler<? super T> exceptionHandler,
        final Sequence workSequence)
    {
        this.ringBuffer = ringBuffer;
        this.sequenceBarrier = sequenceBarrier;
        this.workHandler = workHandler;
        this.exceptionHandler = exceptionHandler;
        this.workSequence = workSequence;

        if (this.workHandler instanceof EventReleaseAware)
        {
            ((EventReleaseAware) this.workHandler).setEventReleaser(eventReleaser);
        }

        timeoutHandler = (workHandler instanceof TimeoutHandler) ? (TimeoutHandler) workHandler : null;
    }

    @Override
    public Sequence getSequence()
    {
        return sequence;
    }

    @Override
    public void halt()
    {
        running.set(false);
        sequenceBarrier.alert(); //唤醒卡在WaitStrategy的Processor线程，好让它知道“结束”状态
    }

    /**
     * remove workProcessor dynamic without message lost
     */
    public void haltLater()
    {
        running.set(false);  //所谓later，就是等待下一次检查的时候才推出，如果处于卡在WaitStrategy，则等待它返回后才检查
    }

    @Override
    public boolean isRunning()
    {
        return running.get();
    }

    /**
     * It is ok to have another thread re-run this method after a halt().
     *
     * @throws IllegalStateException if this processor is already running
     */
    @Override
    public void run()
    {
        if (!running.compareAndSet(false, true))  //防止run方法重复调用造成的问题
        {
            throw new IllegalStateException("Thread is already running");
        }
        sequenceBarrier.clearAlert();

        notifyStart();

        boolean processedSequence = true;
        long cachedAvailableSequence = Long.MIN_VALUE;
        long nextSequence = sequence.get();
        T event = null;
        while (true)  //死循环
        {
            try
            {
                // if previous sequence was processed - fetch the next sequence and set
                // that we have successfully processed the previous sequence
                // typically, this will be true
                // this prevents the sequence getting too far forward if an exception
                // is thrown from the WorkHandler

                if (processedSequence)
                {
                    if (!running.get()) //如果检查到已关闭，则唤醒在同一个Barrier上的其他processor线程
                    {
                        sequenceBarrier.alert();  //唤醒其他线程
                        sequenceBarrier.checkAlert(); //抛出异常，终结此线程
                    }
                    processedSequence = false;
                    do
                    {
                        //workSequence可能和多个Processor共用
                        nextSequence = workSequence.get() + 1L;
                        //这个sequence才是当前处理器处理过的序号，生产者判断尾指针的时候就是按照这个来的，这个就是gatingSequence
                        //拿到下一个新序号的时候，说明workSequence前一个数据已经处理过了
                        sequence.set(nextSequence - 1L);
                    }
                    //由于workSequence可能由多个Processor共用，故存在竞争情况，需要使用CAS
                    while (!workSequence.compareAndSet(nextSequence - 1L, nextSequence));
                }

                //如果没有超过生产者的最大游标，则表明数据可取
                if (cachedAvailableSequence >= nextSequence)
                {
                    //取出序号对应位置的数据
                    event = ringBuffer.get(nextSequence);
                    //交给handler处理
                    workHandler.onEvent(event);
                    processedSequence = true;
                }
                else
                {
                    //阻塞等待下一个可用的序号
                    //如果就是nextSequence，就返回nextSequence
                    //如果可用的大于nextSequence，则返回最新可用的sequence
                    cachedAvailableSequence = sequenceBarrier.waitFor(nextSequence);
                }
            }
            catch (final TimeoutException e)
            {
                notifyTimeout(sequence.get());
            }
            catch (final AlertException ex) //checkAlert()抛出的
            {
                if (!running.get()) //如果已经结束，则终结循环，线程任务结束
                {
                    break;
                }
            }
            catch (final Throwable ex) //其他异常，则交给异常处理器处理
            {
                // handle, mark as processed, unless the exception handler threw an exception
                exceptionHandler.handleEventException(ex, nextSequence, event);
                processedSequence = true;
            }
        }

        notifyShutdown();

        running.set(false);
    }

    private void notifyTimeout(final long availableSequence)
    {
        try
        {
            if (timeoutHandler != null)
            {
                timeoutHandler.onTimeout(availableSequence);
            }
        }
        catch (Throwable e)
        {
            exceptionHandler.handleEventException(e, availableSequence, null);
        }
    }

    private void notifyStart()
    {
        if (workHandler instanceof LifecycleAware)
        {
            try
            {
                ((LifecycleAware) workHandler).onStart();
            }
            catch (final Throwable ex)
            {
                exceptionHandler.handleOnStartException(ex);
            }
        }
    }

    private void notifyShutdown()
    {
        if (workHandler instanceof LifecycleAware)
        {
            try
            {
                ((LifecycleAware) workHandler).onShutdown();
            }
            catch (final Throwable ex)
            {
                exceptionHandler.handleOnShutdownException(ex);
            }
        }
    }
}

public final class WorkerPool<T>
{
    private final AtomicBoolean started = new AtomicBoolean(false);
    private final Sequence workSequence = new Sequence(Sequencer.INITIAL_CURSOR_VALUE); //从-1开始
    private final RingBuffer<T> ringBuffer; //RingBuffer引用，用于构造Processor，取数据
    // WorkProcessors are created to wrap each of the provided WorkHandlers
    private final WorkProcessor<?>[] workProcessors;
    //...
    public WorkerPool(
        final RingBuffer<T> ringBuffer,
        final SequenceBarrier sequenceBarrier,
        final ExceptionHandler<? super T> exceptionHandler,
        final WorkHandler<? super T>... workHandlers)
    {
        this.ringBuffer = ringBuffer;
        final int numWorkers = workHandlers.length;
        workProcessors = new WorkProcessor[numWorkers];

        //每个handler构造一个Processor
        for (int i = 0; i < numWorkers; i++)
        {
            workProcessors[i] = new WorkProcessor<>(
                ringBuffer,
                sequenceBarrier, //共用同一个sequenceBarrier
                workHandlers[i],
                exceptionHandler,
                workSequence); //共用同一个workSequence
        }
    }

    //...
}

public class Disruptor<T>
{
    private final RingBuffer<T> ringBuffer;
    private final Executor executor;
    private final ConsumerRepository<T> consumerRepository = new ConsumerRepository<>();
    private final AtomicBoolean started = new AtomicBoolean(false);
    private ExceptionHandler<? super T> exceptionHandler = new ExceptionHandlerWrapper<>();

    //...

    public final EventHandlerGroup<T> handleEventsWithWorkerPool(final WorkHandler<T>... workHandlers)
    {
        return createWorkerPool(new Sequence[0], workHandlers);
    }

    EventHandlerGroup<T> createWorkerPool(
        final Sequence[] barrierSequences, final WorkHandler<? super T>[] workHandlers)
    {
        final SequenceBarrier sequenceBarrier = ringBuffer.newBarrier(barrierSequences);
        final WorkerPool<T> workerPool = new WorkerPool<>(ringBuffer, sequenceBarrier, exceptionHandler, workHandlers);


        consumerRepository.add(workerPool, sequenceBarrier); //将workPool存入Repository，启动的时候会从Repository中取出，交给Executor处理

        final Sequence[] workerSequences = workerPool.getWorkerSequences();

        updateGatingSequencesForNextInChain(barrierSequences, workerSequences);

        return new EventHandlerGroup<>(this, consumerRepository, workerSequences);
    }

    //....

}

 final class ProcessingSequenceBarrier implements SequenceBarrier
{
    private final WaitStrategy waitStrategy;
    private final Sequence dependentSequence;
    private volatile boolean alerted = false;
    private final Sequence cursorSequence;
    private final Sequencer sequencer;

    //...
    public long waitFor(final long sequence)
        throws AlertException, InterruptedException, TimeoutException
    {
        checkAlert();

        long availableSequence = waitStrategy.waitFor(sequence, cursorSequence, dependentSequence, this);

        if (availableSequence < sequence)
        {
            return availableSequence;
        }

        return sequencer.getHighestPublishedSequence(sequence, availableSequence);
    }
    //...
}

public RingBuffer<T> start()
    {
        checkOnlyStartedOnce();
        for (final ConsumerInfo consumerInfo : consumerRepository)
        {
            consumerInfo.start(executor);
        }

        return ringBuffer;
    }

public class Disruptor<T>
{
    //...
    public Disruptor(final EventFactory<T> eventFactory, final int ringBufferSize, final ThreadFactory threadFactory)
    {
        this(RingBuffer.createMultiProducer(eventFactory, ringBufferSize), new BasicExecutor(threadFactory));
    }
    //...
}

public class BasicExecutor implements Executor
{
    private final ThreadFactory factory;
    private final Queue<Thread> threads = new ConcurrentLinkedQueue<>();

    public BasicExecutor(ThreadFactory factory)
    {
        this.factory = factory;
    }

    @Override
    public void execute(Runnable command)
    {
        //每提交一个任务就新建一个新的线程处理这个任务
        final Thread thread = factory.newThread(command);
        if (null == thread)
        {
            throw new RuntimeException("Failed to create thread to run: " + command);
        }

        thread.start();

        threads.add(thread);
    }
    //...
}