Github user HeartSaVioR commented on the issue: https://github.com/apache/storm/pull/2829 If my understanding is right, there's pendingEmits (unbounded) which comes into play when it can't push tuple immediately, so emit should not block, nextTuple should not block as well. If emit can block in spout it could be pretty much a big risk (ack/fail is not handled as well and tuples will fail into timeout, and it may raise backpressure again). @roshannaik Could you confirm?
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