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From Michael Segel <michael_se...@hotmail.com>
Subject Re: HBase coprocessor callback for comet
Date Wed, 06 Feb 2013 12:39:47 GMT
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

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... 


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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