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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

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


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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