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From Jan Althaus <altha...@gmail.com>
Subject Re: HBase coprocessor callback for comet
Date Wed, 06 Feb 2013 20:12:14 GMT
Thanks for the help everyone.
Would you see this as something that could be useful to ship with HBase? If
so, I may well consider what I'm about to write a proof of concept and post
again with my findings / the source.


On 7 February 2013 01:39, Michael Segel <michael_segel@hotmail.com> wrote:

> I'd say add some sort of durable queue to receive the alert if you don't
> want to miss a message.
>
> Essentially use a region server observer and write the alert to your
> favorite pub/sub solution.
> The key then is starting the pub/sub queue, first so that your region
> server can connect to it.
>
> If you want to get fancy, there's a bit of overkill that you could do...
>  like figure out a way to write the output to HDFS if that made sense.
>
> Just some thoughts before I'm really awake...
>
> -Mike
>
> On Feb 5, 2013, at 10:45 PM, Andrew Purtell <apurtell@apache.org> wrote:
>
> > You are better off using your own RPC. Thrift would be a good choice.
> >
> > On Tuesday, February 5, 2013, Jan Althaus wrote:
> >
> >> Sorry for breaking the thread. It seems my subscription wasn't active at
> >> the time the reply was posted.
> >>
> >> The client receiving the notifications would be a separate process,
> >> potentially on a different machine. It could obviously connect to the
> HBase
> >> cluster though.
> >>
> >> I can certainly see how delivering such notifications would be outside
> the
> >> scope of HBase, but I wanted to make sure that I wasn't reinventing the
> >> wheel by using a completely different RPC mechanism between the region
> >> server and the servlet.
> >>
> >>> Please be a little more specific about where the notifications should
> be
> >>> received.
> >>>
> >>> Your custom RegionObserver lives on region server.
> >>>
> >>> I guess you want notifications to be delivered to your client, outside
> >> the
> >>> cluster.
> >>>
> >>> Cheers
> >>>
> >>> On Tue, Feb 5, 2013 at 12:18 PM, Jan Althaus <althausj@gmail.com
> <javascript:;>>
> >> wrote:
> >>>
> >>>> Hi,
> >>>>
> >>>> I would like to feed a servlet that is serving a long polling request
> >> with
> >>>> notifications when certain rows in an hbase table change.
> >>>>
> >>>> It seems that the best mechanism to achieve this would be to add a
> >> custom
> >>>> RegionObserver. What I'm unsure about though is how to best issue the
> >>>> callback. Does hbase provide an RPC mechanism that I could re-use or
> >> should
> >>>> I consider this a separate problem entirely? Are there alternative
> ways
> >> to
> >>>> get notified of row changes that better handle this problem?
> >>>>
> >>>> Thanks!
> >>>> Jan
> >>>>
> >>
> >
> >
> > --
> > Best regards,
> >
> >   - Andy
> >
> > Problems worthy of attack prove their worth by hitting back. - Piet Hein
> > (via Tom White)
>
>

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