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From "Pamecha, Abhishek" <apame...@x.com>
Subject Re: client cache for all region server information?
Date Thu, 23 Aug 2012 06:47:45 GMT
I think for the refresh case, client first uses the older region server derived from its cache
 it then connects to that older  region server which responds with a failure code.  and then
client talks to the zookeeper and then the meta node server to find the new region server
for that key. The client then reissues the original request to the new region server. 

Btw,Client only caches information as needed for its queries and not necessarily for 'all'
region servers. 


i Sent from my iPad with iMstakes 

On Aug 22, 2012, at 23:31, "Lin Ma" <linlma@gmail.com> wrote:

> Hello HBase masters,
> I am wondering whether in current implementation, each client of HBase
> cache all information of region server, for example, where is region server
> (physical hosting machine of region server), and also cache row-key range
> managed by the region server. If so, two more questions,
> - will there be too much overhead (e.g. memory footprint) of each client?
> - when such information is downloaded and cached at client side, and when
> the information is refreshed (does it only triggered by region server
> change and failure to fetch such information from client -- e.g. when
> client use cache to access machine A for region B, but find nothing, so the
> client needs to refresh the information in cache to see which machine owns
> region B)?
> regards,
> Lin

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