Github user rtudoran commented on the issue:
https://github.com/apache/flink/pull/3641
@fhueske Thanks for the example. First of all i am happy that we agree that
we need to emit something for every input :). I was scared that this will not
be the case
Now regarding the 2 options for the output - i would still have a
preference for the first option. The reason for this is that at least in the
case of proctime there is no 2 events that are simultaneous in absolute terms.
There is an implicit serialization (also based on how flink engine works...one
event will arrive before the other). It might simply be a coincidence that the
granularity that the computers now cannot measure system time with more fine
granularity...and because of that we would have 2 events which are apparently
with the same proc time stamp...
However, as you mentioned several times (and i agree) having a uniform
behavior might be a key point. In this case we would indeed implement the
behavior you suggested. - Let me know again if you are sure about this. I
raised my concerns but i am open to accept what you suggest.
In case you suggest to implement it with proctimes, i have 2 questions:
1) do you know if there is some example for timer in proc time (if not, now
problem - i will figure it out)
2) in the case of harness tests - the correct implementation of the
behavior might not match the test. If i write a test that does
{code}
testHarness.setProcessingTime(3)
testHarness.processElement(new StreamRecord(rInput, 1001)) // let us
assume that the system time is 1490906681
testHarness.processElement(new StreamRecord(rInput, 2002)) // let us
assume that the system time is still 1490906681
+ testHarness.processElement(new StreamRecord(rInput, 2003)) // let us
assume that the system time is now 1490906682
+ testHarness.processElement(new StreamRecord(rInput, 2004)) // let us
assume that the system time is now 1490906682
{code}
in this case if we do a Count, than the output would be
ev1 2
ev2 2
ev3 2
ev4 2
...instead of having all with an associated count of 4 (which would be in
the behavior you mention). This would be because i would assume that the timer
+1ms would be triggered based on system time.
In such a case - should we just build a limited test that would work?
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