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From Gary Helmling <ghelml...@gmail.com>
Subject Re: Is NotServingRegionException really an Exception?
Date Wed, 31 Mar 2010 15:02:20 GMT
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
> >>
> >
>
>

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