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From Adam Gilmore <dragoncu...@gmail.com>
Subject Re: Drill favouring a particular Drillbit
Date Thu, 26 Mar 2015 01:54:00 GMT
We actually setup a separate load balancer for port 8047 (we're submitting
these queries via the REST API at the moment) so Zookeeper etc. is out of
the equation, thus I doubt we're hitting DRILL-2512.

When shutitng down the "troublesome" drillbit, it starts parallelizing much
nicer again.  We even added 10+ nodes to the cluster and as long as that
particular drillbit is shut down, it distributes very nicely.  The minute
we start the drillbit on that node again, it starts swamping it with work.

I'll shoot through the JSON profiles and some more information on the
dataset etc. later today (Australian time!).

On Thu, Mar 26, 2015 at 5:31 AM, Steven Phillips <sphillips@maprtech.com>
wrote:

> I didn't notice at first that Adam said "no matter who the foreman is".
>
> Another suspicion I have is that our current logic for assigning work will
> assign to the exact same nodes every time we query a particular table.
> Changing affinity factor may change it, but it will still be the same every
> time. That is my suspicion, but I am not sure why shutting down the
> drillbit would improve performance. I would expect that shutting down the
> drillbit would result in a different drillbit becoming the hotspot.
>
> On Wed, Mar 25, 2015 at 12:16 PM, Jacques Nadeau <jacques@apache.org>
> wrote:
>
> > On Steven's point, the node that the client connects to is not currently
> > randomized.  Given your description of behavior, I'm not sure that you're
> > hitting 2512 or just general undesirable distribution.
> >
> > On Wed, Mar 25, 2015 at 10:18 AM, Steven Phillips <
> sphillips@maprtech.com>
> > wrote:
> >
> > > This is a known issue:
> > >
> > > https://issues.apache.org/jira/browse/DRILL-2512
> > >
> > > On Wed, Mar 25, 2015 at 8:13 AM, Andries Engelbrecht <
> > > aengelbrecht@maprtech.com> wrote:
> > >
> > > > What version of Drill are you running?
> > > >
> > > > Any hints when looking at the query profiles? Is the node that is
> being
> > > > hammered the foreman for the queries and most of the major fragments
> > are
> > > > tied to the foreman?
> > > >
> > > > —Andries
> > > >
> > > >
> > > > On Mar 25, 2015, at 12:00 AM, Adam Gilmore <dragoncurve@gmail.com>
> > > wrote:
> > > >
> > > > > Hi guys,
> > > > >
> > > > > I'm trying to understand how this could be possible.  I have a
> Hadoop
> > > > > cluster of a name node and two data nodes setup.  All have
> identical
> > > > specs
> > > > > in terms of CPU/RAM etc.
> > > > >
> > > > > The two data nodes have a replicated HDFS setup where I'm storing
> > some
> > > > > Parquet files.
> > > > >
> > > > > A Drill cluster (with Zookeeper) is running with Drillbits on all
> > three
> > > > > servers.
> > > > >
> > > > > When I submit a query to *any* of the Drillbits, no matter who the
> > > > foreman
> > > > > is, one particular data node gets picked to do the vast majority
of
> > the
> > > > > work.
> > > > >
> > > > > We've even added three more task nodes to the cluster and
> everything
> > > > still
> > > > > puts a huge load on one particular server.
> > > > >
> > > > > There is nothing unique about this data node.  HDFS is fully
> > replicated
> > > > (no
> > > > > unreplicated blocks) to the other data node.
> > > > >
> > > > > I know that Drill tries to get data locality, so I'm wondering if
> > this
> > > is
> > > > > the cause, but this essentially swamping this data node with 100%
> CPU
> > > > usage
> > > > > while leaving the others barely doing any work.
> > > > >
> > > > > As soon as we shut down the Drillbit on this data node, query
> > > performance
> > > > > increases significantly.
> > > > >
> > > > > Any thoughts on how I can troubleshoot why Drill is picking that
> > > > particular
> > > > > node?
> > > >
> > > >
> > >
> > >
> > > --
> > >  Steven Phillips
> > >  Software Engineer
> > >
> > >  mapr.com
> > >
> >
>
>
>
> --
>  Steven Phillips
>  Software Engineer
>
>  mapr.com
>

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