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From Fazool <fazoolm...@gmail.com>
Subject Re: Reading from client buffer
Date Thu, 19 May 2011 21:49:13 GMT
Agreed.

On Thu, May 19, 2011 at 11:15 PM, Jean-Daniel Cryans <jdcryans@apache.org>wrote:

> You would still have "confirmed" writes that may never get to the
> server, which comes back to my point that the buffer shouldn't be used
> in this case.
>
> J-D
>
> On Thu, May 19, 2011 at 1:56 PM, Fazool <fazoolmein@gmail.com> wrote:
> > Another way would be that when you read, check the write buffer. If it is
> a
> > hit, flush the buffer, and then return the read.
> >
> > This way, bulk loads will still work, and occasionally, we might have a
> > slower read.
> >
> >
> > On Thu, May 19, 2011 at 9:14 PM, Jean-Daniel Cryans <jdcryans@apache.org
> >wrote:
> >
> >> The write buffer is a hack for faster write performance during bulk
> >> loads, no one should use it in a situation like you described.
> >>
> >> Even if the client was able to read from it's own buffer, the edits
> >> didn't make it to the region server so the other clients wouldn't be
> >> able to see that new data either. Now let's suppose the client died
> >> before flushing, well you would be serving data that actually never
> >> existed!
> >>
> >> I think we should just fix the documentation.
> >>
> >> J-D
> >>
> >> On Thu, May 19, 2011 at 8:02 AM, fazool mein <fazoolmein@gmail.com>
> wrote:
> >> > Hi,
> >> >
> >> > I am going through the Hbase code to understand its properties better.
> >> >
> >> > There is something called 'write buffer' on the client side. Say it is
> >> > enabled. Now, assume a client puts value v under key k, and
> immediately
> >> > reads k.
> >> >
> >> > As I understand from the code, the put will be stored in the client
> side
> >> > write buffer, while the read will go to the region server, returing an
> >> older
> >> > value, instead of v.
> >> >
> >> > Doesn't this violate the ACID semantics (visibility in particular ) of
> >> Hbase
> >> > given at: http://hbase.apache.org/acid-semantics.html
> >> >
> >> > <quote>
> >> >
> >> > When a client receives a "success" response for any mutation, that
> >> mutation
> >> > is immediately visible to both that client and any client with whom it
> >> later
> >> > communicates through side channels.
> >> >
> >> > </quote>
> >> >
> >> > Thanks.
> >> >
> >> > Regards
> >> >
> >>
> >
>

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