Disruptor之ExceptionHandler

Disruptor的版本3.4.2.

List-1

public interface ExceptionHandler<T>
{
    /**
     * <p>Strategy for handling uncaught exceptions when processing an event.</p>
     *
     * <p>If the strategy wishes to terminate further processing by the {@link BatchEventProcessor}
     * then it should throw a {@link RuntimeException}.</p>
     *
     * @param ex       the exception that propagated from the {@link EventHandler}.
     * @param sequence of the event which cause the exception.
     * @param event    being processed when the exception occurred.  This can be null.
     */
    void handleEventException(Throwable ex, long sequence, T event);

    /**
     * Callback to notify of an exception during {@link LifecycleAware#onStart()}
     *
     * @param ex throw during the starting process.
     */
    void handleOnStartException(Throwable ex);

    /**
     * Callback to notify of an exception during {@link LifecycleAware#onShutdown()}
     *
     * @param ex throw during the shutdown process.
     */
    void handleOnShutdownException(Throwable ex);
}

如List-1所示，它是个接口，定义了异常抛出时回调的方法。

如下List-2所示，Disruptor中默认使用ExceptionHandler的ExceptionHandlerWrapper实现，如List-3所示，使用了代理，委托内部的delete来处理。

List-2

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<>();
...

List-3

public class ExceptionHandlerWrapper<T> implements ExceptionHandler<T>
{
    private ExceptionHandler<? super T> delegate = new FatalExceptionHandler();

    public void switchTo(final ExceptionHandler<? super T> exceptionHandler)
    {
        this.delegate = exceptionHandler;
    }
...

除了ExceptionHandlerWrapper这个实现，还有其它FatalExceptionHandler、IgnoreExceptionHandler，IgnoreExceptionHandler只是将异常打印下，但是FatalExceptionHandler则不同，正如其名字所示，它内部将异常再次封装到RuntimeException再次抛出，如下List-4

List-4

public final class FatalExceptionHandler implements ExceptionHandler<Object>
{
    private static final Logger LOGGER = Logger.getLogger(FatalExceptionHandler.class.getName());
    private final Logger logger;

    public FatalExceptionHandler()
    {
        this.logger = LOGGER;
    }

    public FatalExceptionHandler(final Logger logger)
    {
        this.logger = logger;
    }

    @Override
    public void handleEventException(final Throwable ex, final long sequence, final Object event)
    {
        logger.log(Level.SEVERE, "Exception processing: " + sequence + " " + event, ex);

        throw new RuntimeException(ex);
    }
...

如果使用了FatalExceptionHandler，运行中抛出异常，那么会时Disruptor线程阻塞的。ExceptionHandlerWrapper和BatchEventProcessor中exceptionHandler都默认使用了FatalExceptionHandler，所以要特别注意。

来源：oschina

链接：https://my.oschina.net/u/2518341/blog/4300905

标签

Sequence

java

superT

delegate

Disruptor