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From "David chen" <c77...@163.com>
Subject Re: How to know the root reason to cause RegionServer OOM?
Date Wed, 20 May 2015 08:46:17 GMT
Thanks Ted,
For scenario #1, can not see any clues in regionserver log file that denotes "kill -9" command
was executed. Meanwhile, i think when JVM inspects regionserver process OOME, it will create
a new thread to execute "kill -9 %p", the new thread should not write regionserver log, so
the fact, there is not any clues in regionserver log, is normal. Right?
For scenario #2, dmesg also did not provide any clues. But some clues were seen in /var/log/messages:
May 14 12:00:38 localhost kernel: Out of memory: Kill process 22827 (java) score 497 or sacrifice
May 14 12:00:38 localhost kernel: Killed process 22827, UID 483, (java) total-vm:17569220kB,
anon-rss:16296276kB, file-rss:240kB
The 22827 above is regionserver PID.
It looks like regionserver itself OOM(total-vm:17569220kB, anon-rss:16296276kB, the max-heap-size
set is 15G), so was killed. Right?
But hbase has no heavy load in the cluster, so i don't think it was killed because of itself
OOME, instead i think because of lack of memory for other applications, so OS kill regionserver
to run more applications. 
I currently has no evidence to prove my idea, so hope more helps. Thanks.

At 2015-05-20 10:04:19, "Ted Yu" <yuzhihong@gmail.com> wrote:
>For scenario #1, you would see in the regionserver.out file that "kill -9 "
>command was applied due to OOME.
>For scenario #2, can you see if dmesg provides some clue ?
>On Tue, May 19, 2015 at 6:32 PM, David chen <c77_cn@163.com> wrote:
>> Thanks for guys reply, its indeed helped me.
>> Another question, I think there are two possibilities to kill RegionServer
>> process:
>> 1. When JVM inspects that the memory, RegionServer has occupied, exceed
>> the max-heap-size,  then JVM calls positively the command configured by
>> option "-XX:OnOutOfMemoryError=kill -9 %p" to kill RegionServer  process.
>> 2. RegionServer process does not reach the max-heap-size, but new
>> application need to allocation memory,  if lack of memory, OS will choose
>> to kill some processes, RegionServer unfortunately becomes the first
>> choice, so it  is killed by OS.
>> Is my understanding right? If so, how to know which possibility my scene
>> is?
>> Any ideas can be appreciated!
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