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From Lin Ma <lin...@gmail.com>
Subject Re: client cache for all region server information?
Date Thu, 23 Aug 2012 11:01:03 GMT
Thank you Abhishek,

Two more comments,

-- "Client only caches information as needed for its queries and not
necessarily for 'all' region servers." -- how did client know which region
server information is necessary to be cached in current HBase
implementation?

-- When the client loads region server information for the first time? Did
client persistent cache information at client side about region server
information?

regards,
Lin

On Thu, Aug 23, 2012 at 2:47 PM, Pamecha, Abhishek <apamecha@x.com> wrote:

> 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.
>
> Abhishek
>
>
> 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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