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From Mikael Sitruk <mikael.sit...@gmail.com>
Subject Re: ANN: The third hbase 0.94.0 release candidate is available for download
Date Sat, 12 May 2012 22:14:50 GMT
Hi St.Ack
You asked for it :-)
So in case a RS goes down, the master will split the log and reassign the
regions to other RS, then each RS will replay the log, during this step the
regions are unavailable, and clients will got exceptions.
1. how the master will choose a RS to assign a region?
2. how many RS will be involved in this reassignment
3. client that got exception should renew their connections or they can
reuse the same one?
4. is there a way to figure out how long this split+replay will take
(either by formula at the design time of a deployment, or at runtime via
API asking the master for example)???

Thanks again
Mikael.S


On Sun, May 13, 2012 at 12:50 AM, Stack <stack@duboce.net> wrote:

> On Sat, May 12, 2012 at 10:14 AM, Mikael Sitruk <mikael.sitruk@gmail.com>
> wrote:
> > Thanks for the clarifications St.Ack.
> > Still I have some questions in regards of 3 in scenario discussed -
>  when a
> > region is offline it means that client operation are not possible on it
> > (even read)?
>
> Correct.
>
> > In case a second master is up (in an environment with multiple master), i
> > presume all this occurs unless the second master (slave) become the
> master,
> > right? how long those it take for a "slave" master to become a master??
> >
>
> It takes seconds roughly for new master to assume master role and to
> figure the state of the cluster.
>
> The processing of a failed server though can take seconds, minutes, or
> even hours at an extreme where the server was running with
> pathological configs.  How long to process WALs is a function of the
> number of WAL files the server was carrying in need of replay and the
> number of servers available to participate in the distributed log
> splitting affair.
>
> Ask more questions Mikael,
> St.Ack
>

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