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From Omer Hadari <hadari.o...@gmail.com>
Subject Re: Drop event disordering
Date Wed, 22 Nov 2017 18:39:55 GMT
Yes we were thinking in that direction as well, that’s why I mentioned the
1ms part. I do not know how events are assigned an ordinal though, so it’s
unclear to me whether the disordering is constant but is usually “hidden”
since there is no rollover, or maybe there is some kind of a race
condition. You’ll probably be able to answer these questions quicker than
me, I’ll open a jira as soon as I get home later today.

Thanks again!

On Wed, 22 Nov 2017 at 20:34 Mark Payne <markap14@hotmail.com> wrote:

> Omer,
>
> Yes, I think that is sufficient. I think the issue is that the framework
> is creating both the
> ATTRIBUTES_MODIFIED and DROP events, and the generation of these objects is
> very fast. But if the timestamp happens to 'rollover' from millisecond 1
> to millisecond 2,
> for example, those events get different timestamps. So I think it's just a
> timing thing that
> will be somewhat difficult to reproduce reliably. But just a description
> of the behavior that
> you're experiencing should be fine.
>
> Thanks
> -Mark
>
> On Nov 22, 2017, at 1:04 PM, Omer Hadari <hadari.omer@gmail.com> wrote:
>
> I’ll be glad to open a jira, though the problem is hardly coherent imo,
> what would you like to see there? Simply “Disordering of drop events” and
> the explanation I have here? Sadly I cannot provide a concrete example
> since the problem does not reproduce.
>
> On Wed, 22 Nov 2017 at 18:23 Joe Witt <joe.witt@gmail.com> wrote:
>
>> also - awesome find!  And glad you're at such a level with provenance
>> data to catch that.  Thanks Omer!
>>
>> On Wed, Nov 22, 2017 at 11:21 AM, Mark Payne <markap14@hotmail.com>
>> wrote:
>> > Omer,
>> >
>> > This is likely an issue related to the order in which we generate those
>> events in the framework.
>> > Do you mind filing a JIRA?
>> >
>> > Thanks
>> > -Mark
>> >
>> >
>> >> On Nov 22, 2017, at 10:51 AM, Omer Hadari <hadari.omer@gmail.com>
>> wrote:
>> >>
>> >> Hi!
>> >> We’ve been using NiFi for a while now, and we save all provenance
>> events for logging purposes and such. We encountered an issue while looking
>> at lineages of some flow files, which showed drop events as if they
>> happened before another event, that in fact preceded it (and indeed has a
>> lower event ordinal).
>> >>
>> >> For example in a split json processor, the original FlowFile is
>> dropped after all splits happen and are assigned fragment counts, but still
>> the timestamp of the drop event is earlier than the timestamp of the
>> attributes modified event. That causes the graph to look as if the
>> attributes modified event comes out of the drop event, which doesn’t really
>> make sense to us (should it?). It’s probably worth noting that the drop
>> event ordinal is higher than the attributes modified event ordinal. Also we
>> noticed that
>> >> 1. This only happens every once per a few thousand events.
>> >> 2. This does not reproduce by replaying.
>> >> 3. The drop event’s timestamp is earlier by 1ms in the cases we
>> encountered, and the ordinal is always larger by one.
>> >>
>> >> This might be an error with the split json processor or a more general
>> one. We’d love any clues or corrections to misconceptions we might have
>> (maybe this is not a problem and drop events can precede other events?)
>> >>
>> >> Thank you!
>> >
>>
>
>

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