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From Ariel Marcus <ariel.mar...@openbi.com>
Subject Re: delay before query starts processing
Date Wed, 30 Jan 2013 23:22:53 GMT
>From the archives:
http://mail-archives.apache.org/mod_mbox/hive-user/201110.mbox/%3CCAC9SPjuQtxOK1KtEmReD6OanNTgNM_uLkGQD+=n7KRcJcaLmGw@mail.gmail.com%3E

TL;DR set hive.optimize.s3.query=true;

---------------------------------
Ariel Marcus, Consultant
www.openbi.com | ariel.marcus@openbi.com
150 N Michigan Avenue, Suite 2800, Chicago, IL 60601
Cell: 314-827-4356


On Wed, Jan 30, 2013 at 6:16 PM, Marc Limotte <mslimotte@gmail.com> wrote:

> Hi,
>
> I'm running in Amazon on an EMR cluster with hive 0.8.1.  We have a lot of
> other Hadoop jobs, but only started experimenting with Hive recently.
>
> I've been seeing a long pause after submitting a hive query and the
> actually start of the hadoop job... 10 minutes or more in some cases.  I'm
> wondering what's happening during this time.  Either a high level answer,
> or maybe there is some logging I can turn on?
>
> Here's some more detail.  I submit the query on the master using the hive
> cli, and start to see some output right away...
>
> Total MapReduce jobs = 2
> Launching Job 1 out of 2
> Number of reduce tasks not specified. Estimated from input data size: 1
> In order to change the average load for a reducer (in bytes):
>   set hive.exec.reducers.bytes.per.reducer=<number>
> In order to limit the maximum number of reducers:
>   set hive.exec.reducers.max=<number>
> In order to set a constant number of reducers:
>   set mapred.reduce.tasks=<number>
>
>
> *[then a long delay here: 10 minutes or more... no activity in the hadoop
> job tracker ui] *
>
>
> … and then it continues normally ...
> Starting Job = job_201301160029_0082, Tracking URL =
> http://ip-xxxxxxxx.ec2.internal:9100/jobdetails.jsp?jobid=job_201301160029_0082
> Kill Command = /home/hadoop/bin/hadoop job
>  -Dmapred.job.tracker=xxxxxx:9001 -kill job_201301160029_0082
> Hadoop job information for Stage-1: number of mappers: 2; number of
> reducers: 1
> 2013-01-30 20:45:30,526 Stage-1 map = 0%,  reduce = 0%
> …
>
> This query is processing in the neighborhood of 500GB of data from S3.  A
> couple of possibilities I thought of… perhaps someone can confirm or deny:
> a) Is the data copied from S3 to HDFS during this time?
> b) I have a fairly large set of libs in HIVE_AUX_JAR_PATH (around ~175
> MB)-- does it have to copy these around to the tasks at this time?
>
> Any insights appreciated.
>
> Marc
>
>
>
>
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