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From: Joe Witt <joe.witt@gmail.com>
Date: Mon, 11 Dec 2017 08:58:06 -0500
Message-ID: <CALJK9a5vkus6-XLf_uH7A5U+k1CTL4bTqjJz6WzN+9RfGx+a3A@mail.gmail.com>
Subject: Re: Drop event disordering
To: users@nifi.apache.org
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archived-at: Mon, 11 Dec 2017 13:58:11 -0000

Omer

It can certainly be looked at in time for 1.5 but based on recent
progress/discussion 1.5 may well kick off rather soon.  It is
something someone would need to take up and that someone need not be a
committer at this point.  Your analysis of the different provenanace
repositories having no real impact is helpful though as it might
suggest the issue lies above during the generation of the events so
that should help narrow it down.

Thanks
Joe

On Mon, Dec 11, 2017 at 8:51 AM, Omer Hadari <hadari.omer@gmail.com> wrote:
> Hi, we have looked into it some more and tried using
> WriteAheadProvenanceRepository, to no real avail. Sorry for the ping, but=
 do
> you have any other ideas? We don=E2=80=99t mind pursuing them and this pr=
oblem is
> critical for us. Any chance this could be looked at for 1.5?
>
> Thanks!
>
> On Fri, 24 Nov 2017 at 13:19 Omer Hadari <hadari.omer@gmail.com> wrote:
>>
>> Opened an issue
>> NIFI-4638
>>
>> On Wed, 22 Nov 2017 at 20:39 Omer Hadari <hadari.omer@gmail.com> wrote:
>>>
>>> Yes we were thinking in that direction as well, that=E2=80=99s why I me=
ntioned
>>> the 1ms part. I do not know how events are assigned an ordinal though, =
so
>>> it=E2=80=99s unclear to me whether the disordering is constant but is u=
sually
>>> =E2=80=9Chidden=E2=80=9D since there is no rollover, or maybe there is =
some kind of a race
>>> condition. You=E2=80=99ll probably be able to answer these questions qu=
icker than
>>> me, I=E2=80=99ll 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 framewo=
rk
>>>> is creating both the
>>>> ATTRIBUTES_MODIFIED and DROP events, and the generation of these objec=
ts
>>>> 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 ju=
st
>>>> a timing thing that
>>>> will be somewhat difficult to reproduce reliably. But just a descripti=
on
>>>> 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=E2=80=99ll be glad to open a jira, though the problem is hardly cohe=
rent imo,
>>>> what would you like to see there? Simply =E2=80=9CDisordering of drop =
events=E2=80=9D 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=E2=80=99ve been using NiFi for a while now, and we save all pro=
venance
>>>>> >> events for logging purposes and such. We encountered an issue whil=
e looking
>>>>> >> at lineages of some flow files, which showed drop events as if the=
y happened
>>>>> >> before another event, that in fact preceded it (and indeed has a l=
ower 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 t=
he
>>>>> >> attributes modified event. That causes the graph to look as if the
>>>>> >> attributes modified event comes out of the drop event, which doesn=
=E2=80=99t really
>>>>> >> make sense to us (should it?). It=E2=80=99s 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=E2=80=99s timestamp is earlier by 1ms in the cas=
es 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=E2=80=99d love any clues or corrections to misconc=
eptions we might
>>>>> >> have (maybe this is not a problem and drop events can precede othe=
r events?)
>>>>> >>
>>>>> >> Thank you!
>>>>> >
>>>>
>>>>
>