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I have a spring application which builds a reactive pipeline as follows:

buildPipeline(). // returns a flux based on changeStreamEvents or Kafka receives
.bufferTimeout( capacity, Duration.ofSeconds(1))
. flatMap( r -> {
   element x = r.get(r.size()-1)
   //some processing on element and the batch obtained
})
.doOnError( e-> log.info("error occurred:" + e.toString())
.subscribe()

However, I see my application intermediately throwing the below error -

java.lang.illegalArgumentException:3.9 While the Subscription is not cancelled, Subscription.request(long n) MUST throw a java.lang.illegalArgumentException if argument <= 0
at com.mongodb.reactivestreams.client.internal.ObservableToPublisher$1
$1.request(ObservableToPublisher.java:43)
at reactor.core.publisher.FluxMap$MapSubscriber.request(FluxMap.java:155)
at reactor.core.publisher.FluxBufferTimeout
$BufferimeoutSubscriber.requestMore(FluxBufferTimeout.java:317)

I'm not able to determine what is wrong, and why the stream is terminating with this error. Any help would be highly appreciated.

The application started throwing this error after I added "bufferTimeout" to add a feature of batching. Before that, I had never encountered this exception. Not sure how to replicate the issue as well, as it is not occurring locally or in UAT, but only in production environment of the application. Any leads would be helpful.

Thanks!

user1803_stacker
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  • can you tell what the value of `capacity` is ? it indeed looks like `BufferTimeoutSubscriber` calls `request` with `0` value or something like that – Simon Baslé Oct 26 '20 at 21:05
  • yes so the value of capacity is 1000. When I added .log(), I did see that the exception was being raised when a request(0) was being done, but I am not able to think why request(0) would invoked? Is it because suppose by the time timeOut duration is reached, and if there are no items in buffer, it requests for 0? – use1803 Oct 27 '20 at 18:38

1 Answers1

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Try adding a onBackPressureBuffer(), so that in case of low demand this operator buffers the requests, and emits items in a controlled way.

use1803
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