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From Jacques Nadeau <jacq...@apache.org>
Subject Re: Drill favouring a particular Drillbit
Date Wed, 25 Mar 2015 18:23:25 GMT
Adam,

There is actually an option to control how much Drill uses locality versus
distribution.  Not sure if that is influencing you but it could be.  If so,
you can decrease the value to increase the importance of distribution.  The
option is `planner.affinity_factor`.



On Wed, 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?
>

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