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From Maxim Zizin <mzi...@gmail.com>
Subject JobTracker memory usage peaks once a day and OOM sometimes
Date Tue, 08 Feb 2011 16:59:34 GMT
Hi all,

We monitor JT, NN and SNN memory usage and observe the following 
behavior in our Hadoop cluster. JT's heap size is set to 2000m. About 18 
hours a day it uses ~1GB but every day roughly at the minute it was 
started its used memory increases to ~1.5GB and then decreases back to 
~1GB in about 6 hours. Sometimes this takes a bit more than 6 hours, 
sometimes a bit less. I was wondering whether anyone here knows what JT 
does once a day that makes it use 1.5 times more memory than normally.

We're so interested in JT memory usage because during last two weeks we 
twice had JT getting out of heap space. Both times right after those 
daily used memory peaks when it was going down from 1.5GB to 1GB it 
started increasing again until got stuck at ~2.2GB. After that it 
becomes unresponsive and we have to restart it.

We're using Cloudera's CDH2 version 0.20.1+169.113.

Regards, Max

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