Github user HeartSaVioR commented on the issue:
https://github.com/apache/storm/pull/2829
@srdo is right. The reason is to enforce "max.spout.pending.limit", but the
concept is brought when backpressure is not in place. IMHO, the concept is the
thing we should drop whenever backpressure is stabilized.
While I'm wondering backpressure would work correctly without any critical
performance hit on 1.x (we disabled by default AFAIK), STORM-2306 renewed the
mechanism of backpressure which we may be OK to rely on backpressure. If my
memory is right, providing "max.spout.pending" was still the way to optimize
even with STORM-2306, but even without this it worked correctly with sane
performance.
At least for Storm 2.0 we could try out relying only backpressure and drop
the concept if we are happy with the result.
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