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 <[email protected]> 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 >>> <[email protected]<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)
