Hi everyone,

I have found a strange behavior in topology metrics.

Let`s say, we have 1 node, 2-core machine. simple Storm topology
Spout A -> Bolt B -> Bolt C

Bolt B splits message on 320 parts and  emits (shuffle grouping) each to
Bolt C. Also Bolts B and C make some read/write operations to db.

Input flow is continuous and static.

Based on logic, setting up a more higher number of executors for Bolt C
than number of cores should be useless (the bigger part of threads will be
sleeping).
It is confirmed by increasing execute and process latency.

But I noticed that complete latency has started to decrease. And I do not
understand why.

For example, stats for bolt C:

ExecutorsProcess latency (ms)Complete latency (ms)25.599897.27646.3526.364
28.432345.454

Is it side effect of IO bound tasks?

Thanks in advance.

-- 
Best regards,
Dmytro Dragan

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