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From Bharath Vissapragada <bhara...@cloudera.com>
Subject Re: Uneven write request to regions
Date Fri, 15 Nov 2013 03:39:19 GMT
How about forcing a region split and moving the splits to RSs with less
load ?


On Fri, Nov 15, 2013 at 7:21 AM, Jia Wang <ramon@appannie.com> wrote:

> Then the case is simple, as i said "check your row key design, you can find
> the start and end row key for each region, from which you can know why your
> request with a specific row key doesn't hit a specified region"
>
> Cheers
> Ramon
>
>
> On Thu, Nov 14, 2013 at 8:47 PM, Asaf Mesika <asaf.mesika@gmail.com>
> wrote:
>
> > It's from the same table.
> > The thing is that some <customerId> simply have less data saved in HBase,
> > while others have x50 (max) data.
> > I'm trying to check how people designed their rowkey around it, or had
> > other out-of-the-box solution for it.
> >
> >
> >
> > On Thu, Nov 14, 2013 at 12:06 PM, Jia Wang <ramon@appannie.com> wrote:
> >
> > > Hi
> > >
> > > Are the regions from the same table? If it was, check your row key
> > design,
> > > you can find the start and end row key for each region, from which you
> > can
> > > know why your request with a specific row key doesn't hit a specified
> > > region.
> > >
> > > If the regions are for different table, you may consider to combine
> some
> > > cold regions for some tables.
> > >
> > > Thanks
> > > Ramon
> > >
> > >
> > > On Thu, Nov 14, 2013 at 4:59 PM, Asaf Mesika <asaf.mesika@gmail.com>
> > > wrote:
> > >
> > > > Hi,
> > > >
> > > > Have anyone ran into a case where a Region Server is hosting regions,
> > in
> > > > which some regions are getting lots of write requests, and the rest
> > gets
> > > > maye 1/1000 of the rate of write requests?
> > > >
> > > > This leads to a situation where the HLog queue reaches its maxlogs
> > limit
> > > > since, those HLogs containing the puts from slow-write regions are
> > > "stuck"
> > > > until the region will flush. Since those regions barely make it to
> > their
> > > > 256MB flush limit (our configuration), they won't flush. The HLogs
> > queue
> > > > gets bigger due to the fast-write regions, until reaches the stress
> > mode
> > > of
> > > > "We have too many logs".
> > > > This in turn flushes out lots of regions, many of them (about 100)
> are
> > > > ultra small (10k - 3mb). After 3 rounds like this, the compaction
> queue
> > > > gets very big....in the end the region server drops dead, and this
> load
> > > > somehow is moved to another RS, ...
> > > >
> > > > We are running 0.94.7 with 30 RS.
> > > >
> > > > I was wondering how did people handled a mix of slow-write-rate and
> > > > high-write-rate of regions in 1 RS? I was thinking of writing a
> > customer
> > > > load balancer, which keeps tabs on the write request count and
> memstore
> > > > size, and move all the slow-write regions to 20% of cluster RS
> > dedicated
> > > to
> > > > slow regions, thus releasing the fast write regions to work freely.
> > > >
> > > > Since this issue is hammering our production, we're about to try to
> > > > shut-down the WAL, and risk losing some information in those
> slow-write
> > > > regions until we can come up with a better solution.
> > > >
> > > > Any advice would be highly appreciated.
> > > >
> > > > Oh - our rowkey is quite normal:
> > > > <customerId><bucket><Timestamp><uniqueId>
> > > >
> > > > Thanks!
> > > >
> > >
> >
>



-- 
Bharath Vissapragada
<http://www.cloudera.com>

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