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From Josh Elser <josh.el...@gmail.com>
Subject Re: Watching for Changes with Write Ahead Log?
Date Tue, 29 Sep 2015 21:52:53 GMT
Speaking from experience of trying to work with the WAL to implement 
data-center replication: I would not recommend trying to use the WALs 
yourself. This is not a fun part of the code to try to reason about and 
it's not designed to be consumed by users. At all.

I would push you to look at Fluo (http://fluo.io).

Using the data-center replication feature 
(http://accumulo.apache.org/1.7/accumulo_user_manual.html#_replication) 
as a notification bus is possible and would hopefully be a bit more 
stable than trying to write it all yourself.

Parise, Jonathan wrote:
> Hi,
>
> I’m working on a system where generally changes to Accumulo will come
> through that system. However, in some cases, another system may change
> data without my system being aware of it.
>
> What I would like to do is somehow listen for changes to the tables my
> system cares about. I know there is a write ahead log that I could
> potentially listen to for changes, but I don’t know how to use it. I
> looked around for some documentation about it, and I don’t see much. I
> get the impression that it isn’t really intended for this type of use case.
>
> Does anyone have any suggestions on how to watch a table for changes and
> then determine if those changes were made by a different system.
>
> Is there some documentation about how to use the write ahead log?
>
> Thanks,
>
> Jon Parise
>

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