Is there a way to seek to a particular event and start processing in event handlers?

Axon Server
,
1

Hi all,

I am creating a new event handler to create a report. The requirement is that I start listening for certain event after a certain date which is pretty much close to the end of our 100M events. I am using the following registration for the handler:

          configurer.registerTrackingEventProcessor(processingGroup, org.axonframework.config.Configuration::eventStore,
              conf -> TrackingEventProcessorConfiguration.forParallelProcessing(projector.getMaxThreads())
                  .andBatchSize(projector.getBatchSize())
                  .andInitialTrackingToken(streamableMessageSource -> streamableMessageSource
                      .createTokenAt(projector.getEventReplayStartAt())))
              .registerHandlerInterceptor(processingGroup, configuration -> new EventHandlerLoggingInterceptor())
              .registerErrorHandler(processingGroup, conf -> projector.newErrorHandler());

This actually does the job but unfortunately it took around 12 hours to “skip” to the events that I need to process. I understand that I can use more threads and a larger batch size to process more events, but it seems to be very inefficient to have to read and skip all the events until the very end. Is there a way that you can recommend me to proceed tackling this? I was thinking if there is a way to just “skip” to a particular event (like a global event index) without reading from the start would be great.

2

Hi @ekyu88,

I believe the createTokenAt method that you used is actually what you are looking for.
I couldn’t deduce the value of your projector.getEventReplayStartAt() but you can probably get a better number for that and make sure you don’t “process” every event.

Check the official docs for more info: Streaming Event Processors - Axon Reference Guide

KR,

3

Hey Lucas,

Thank you for helping. I no longer use the createTokenAt because it does not seem to do the job. I went back and use addInitialTrackingToken(), and instantiate a GlobalSequenceTrackingToken() to identify an event to begin stream (re)play and this seems to be working the way we expect partial event replay would be.

Regards,
Ed.

4

To close this topic, it turns out during the configuration of the tracking processor, java reflection call from a package we used failed causing the event handling class failed to be recognized and configured to handle the events. After removing the reflection code, everything worked.