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From: Christopher <ctubbsii@apache.org>
Date: Thu, 02 Feb 2017 02:54:06 +0000
Message-ID: <CAL5zq9bk9h7-6_x2t+vqvPD0YOtphdbE67ffv=60w-+UT9W95A@mail.gmail.com>
Subject: Re: third party service to poll Fluo for absence of event
To: dev@fluo.incubator.apache.org
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archived-at: Thu, 02 Feb 2017 02:54:53 -0000

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On Wed, Feb 1, 2017 at 10:04 AM Meier, Caleb <Caleb.Meier@parsons.com>
wrote:

> Yeah, this seems pretty reasonable to me.  I guess it then boils down to
> the nitty gritty of do I store results in Fluo and have my service query
> Fluo (I think you guys actually advise against that in your documentation=
),
> or export results and then have the service query some external index tha=
t
> I am exporting to.
>
>
I'm not sure we advise against it, so much as recognize that it may not be
suitable for certain use cases and may not meet query performance
expectations (
http://fluo.apache.org/docs/fluo-recipes/1.0.0-incubating/export-queue/).

In any case, your observer need not write the final "last occurrence"
entries into a Fluo table. It could write them anywhere.


> Regarding timestamps, does the oracle server provide actual timestamps or
> just logical timestamps?  That is, could I use the timestamps that the
> server provides to define some sort of now() function to obtain the curre=
nt
> time to compare with the times of incoming events?
>

Just logical time, and it delivers batches to limit locking, so it can
appear to jump ahead spontaneously. I'm not sure the OracleServer is
suitable for this purpose. What level of precision are you going for? It
might be enough to just run NTP, if you don't need more precision than
"within seconds".


> ________________________________________
> From: Christopher <ctubbsii@apache.org>
> Sent: Tuesday, January 31, 2017 5:08 PM
> To: dev@fluo.incubator.apache.org
> Subject: Re: third party service to poll Fluo for absence of event
>
> You could write an observer which rolls up timestamps from all the events
> you are concerned about, and puts the most recent event timestamp into a
> centralized place, which you could poll. If there is no ingest of these
> events, then the last timestamp in this central place will exceed some
> threshold and the poller could detect that and trigger additional actions=
.
>
> On Tue, Jan 31, 2017 at 3:51 PM Meier, Caleb <Caleb.Meier@parsons.com>
> wrote:
>
> > Hello,
> >
> > I=E2=80=99m looking into using Fluo to develop an event based notificat=
ion system
> > that incrementally generates events of increasing complexity.  The one
> > issue that I=E2=80=99m running into is how to handle the non-event even=
t.  That
> is,
> > Fluo (as I understand it) is not well-suited to handle the following
> > request: =E2=80=9Cgenerate a notification if no events of a given type =
have
> > occurred within the last 24 hours=E2=80=9D.  This is because it is a pu=
sh based
> > notification framework that only generates notifications when things
> > actually happen.  So the question is, has anyone looked into developing=
 a
> > service for generating notifications at regular intervals (even if
> > something doesn=E2=80=99t happen) that works with Fluo?  I=E2=80=99m to=
ying with the idea
> > of creating some sort of Twill application that tells Fluo to wake up a=
t
> > regular intervals to generate a notification about the set of events
> > falling within the given time window. Before doing this I just wanted t=
o
> > make sure that something like this does not already exist, and I also
> want
> > to get a sense of how bad an idea it is to delegate some of the logic o=
f
> > this periodic notification service to Fluo.   Would it be better to
> > separate out the temporal portion of my notification request to be
> > processed entirely outside of Fluo to avoid transactional overhead?
> >
> > Caleb A. Meier, Ph.D.
> > Software Engineer II =E2=99=A6 Analyst
> > Parsons Corporation
> > 1911 N. Fort Myer Drive, Suite 800 =E2=99=A6 Arlington, VA 22209
> > Office:  (703)797-3066 <(703)%20797-3066> <(703)%20797-3066>
> > Caleb.Meier@Parsons.com<mailto:Caleb.Meier@Parsons.com> =E2=99=A6
> www.parsons.com<
> > http://www.parsons.com/>
> >
> > --
> Christopher
>
--=20
Christopher

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