Code Example Disruptor2x

mikeb01 edited this page Oct 4, 2012 · 3 revisions

An example of a single publisher and single event processor for Disruptor 2.x

Code Example for Disruptor 2.x

The code below is an example of a single producer and single consumer using the convenience interface EventHandler for implementing a consumer. The consumer runs on a separate thread receiving entries as they become available.

RingBuffer events as the item of data exchange. These event objects as simple or complex as your application needs.

public final class ValueEvent
{
    private long value;

    public long getValue()
    {
        return value;
    }

    public void setValue(final long value)
    {
        this.value = value;
    }

    public final static EventFactory<ValueEvent> EVENT_FACTORY = new EventFactory<ValueEvent>()
    {
        public ValueEvent newInstance()
        {
            return new ValueEvent();
        }
    };
}

Event processors implement this interface for convenience.

final EventHandler<ValueEvent> handler = new EventHandler<ValueEvent>()
{
    public void onEvent(final ValueEvent event, final long sequence, final boolean endOfBatch) throws Exception
    {
        // process a new event.
    }
};

Setup the RingBuffer and barriers.

RingBuffer<ValueEvent> ringBuffer =
    new RingBuffer<ValueEvent>(ValueEvent.EVENT_FACTORY, 
                               new SingleThreadedClaimStrategy(RING_SIZE),
                               new SleepingWaitStrategy());

SequenceBarrier<ValueEvent> barrier = ringBuffer.newBarrier();       
BatchEventProcessor<ValueEvent> eventProcessor = new BatchEventProcessor<ValueEvent>(barrier, handler);
ringBuffer.setGatingSequences(eventProcessor.getSequence());  

// Each EventProcessor can run on a separate thread
EXECUTOR.submit(eventProcessor);

For most situations, the DSLWizard can be used to simplify the setup. The equivalent ring buffer and processor setup when using the DSLWizard would be:

Disruptor<ValueEvent> disruptor =
  new Disruptor<ValueEvent>(ValueEvent.EVENT_FACTORY, EXECUTOR, 
                            new SingleThreadedClaimStrategy(RING_SIZE),
                            new SleepingWaitStrategy());
disruptor.handleEventsWith(handler);
RingBuffer<ValueEvent> ringBuffer = disruptor.start();

Publisher claims events in sequence for publishing to EventProcessors.

// Publishers claim events in sequence
long sequence = ringBuffer.next();
ValueEvent event = ringBuffer.get(sequence);

event.setValue(1234); // this could be more complex with multiple fields

// make the event available to EventProcessors
ringBuffer.publish(sequence);   

or with the Disruptor DSL:

disruptor.publishEvent(eventTranslator);

where eventTranslator is an instance of the class com.lmax.disruptor.EventTranslator. The translateTo method will be called to copy data into the supplied event from the ring buffer.