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From Jean-Daniel Cryans <jdcry...@apache.org>
Subject Re: Is NotServingRegionException really an Exception?
Date Wed, 31 Mar 2010 16:56:43 GMT
Arber,

If your cluster doesn't recover, it means there's something else going
on. Feel free to start a new thread on this mailing list to discuss
that, posting relevant informations like version, hardware,
configurations and logs.

J-D

On Wed, Mar 31, 2010 at 9:39 AM, Yabo Xu <arber.research@gmail.com> wrote:
> Sorry for interrupting the thread. We also gets the annoying
> NotServingRegionException once in a while ( especially after intensive
> writing), and if it happens, it seems that the only way is to stop all the
> programs and restart HBase.
>
> Any better way to deal with it?  ( I tried flush operation on the shell, but
> it does not work )
>
> Or how to avoid this from happening?
>
> Thanks,
> Arber
>
> On Wed, Mar 31, 2010 at 11:44 PM, Stack <stack@duboce.net> wrote:
>
>> I always thought that the throwing of an exception to signal moved
>> region was broke if only for the reason that it disturbing to new
>> users.  See https://issues.apache.org/jira/browse/HBASE-72
>>
>> Would be nice to change it.  I don't think it easy though.  We'd need
>> to rig the RPC so calls were enveloped or some such so we could pass
>> status messages along with (or instead of) a query results.
>>
>> St.Ack
>>
>>
>> On Wed, Mar 31, 2010 at 8:06 AM, Edward Capriolo <edlinuxguru@gmail.com>
>> wrote:
>> > On Wed, Mar 31, 2010 at 11:02 AM, Gary Helmling <ghelmling@gmail.com>
>> wrote:
>> >
>> >> Well I would still view it as an exceptional condition.  The client
>> asked
>> >> for data back from a server that does not own that data.  Sending back
>> an
>> >> exception seems like the appropriate response, to me at least.  It's
>> just
>> >> an
>> >> exceptional condition that's allowed to happen in favor of the
>> optimization
>> >> of caching region locations in memory on the client.
>> >>
>> >> I could see the reporting of the exception being misleading though if
>> it's
>> >> being logged at an error or warn level when it's a normal part of
>> >> operations.  What's the logging level of the messages?
>> >>
>> >>
>> >> On Wed, Mar 31, 2010 at 10:51 AM, Al Lias <al.lias@gmx.de> wrote:
>> >>
>> >> > Am 31.03.2010 16:47, schrieb Gary Helmling:
>> >> > > NotServingRegionException is a normal part of operations when
>> regions
>> >> > > transition (ie due to splits).  It's how the region server signals
>> back
>> >> > to
>> >> > > the client that it needs to re-lookup the region location in .META.
>> >> > (which
>> >> > > is normally cached in memory by the client, so can become stale).
>> >> > >
>> >> > > I'm sure it can also show up as a symptom of other problems, but
if
>> >> > you're
>> >> > > not seeing any other issues, then it's nothing to be concerned
>> about.
>> >> > >
>> >> >
>> >> > Thx Gary,
>> >> >
>> >> >        this is my point: I see this many times in the (production)
>> logs
>> >> > when
>> >> > it is actually nothing to worry about. Should'nt this rather be a
>> normal
>> >> > response of a region server, instead an Exception?
>> >> >
>> >> > Al
>> >> >
>> >> > >
>> >> > > On Wed, Mar 31, 2010 at 7:38 AM, Al Lias <al.lias@gmx.de>
wrote:
>> >> > >
>> >> > >> As I do see this Exception really often in our logs. I wonder
if
>> this
>> >> > >> indicates a regular thing (within splits etc) or if this is
>> something
>> >> > >> that should not normally happen.
>> >> > >>
>> >> > >> I see it often in Jira as a reason for something else that
fails,
>> but
>> >> > >> for a regular client request, where the client not perfectly
>> >> up-to-date
>> >> > >> with region information it looks as something normal. Am I
right
>> here?
>> >> > >>
>> >> > >>
>> >> > >> Al
>> >> > >>
>> >> > >
>> >> >
>> >> >
>> >>
>> > The LDAP api's throw a ReferralException when you try to update a read
>> only
>> > slave, so heir is a precedence for that. But true that an exception may
>> be
>> > strong for something that is technically a warning.
>> >
>>
>

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