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From "Rendon, Carlos (KBB - Irvine)" <Carlos.Ren...@kbb.com>
Subject RE: Region Server OutOfMemory Error
Date Thu, 08 Jan 2015 17:36:39 GMT
I recently ran into this exact same issue on G1GC. In my case I had the luxury of giving HBase
more heap space. 
If that is an option for you, you might try it out and see if it helps.

-Carlos

-----Original Message-----
From: Shuai Lin [mailto:linshuai2012@gmail.com] 
Sent: Tuesday, January 06, 2015 3:33 AM
To: user@hbase.apache.org
Subject: Region Server OutOfMemory Error

Hi all,

We have a hbase cluster of 5 region servers, each, each hosting 60+ regions.

But under heavy load the region servers crashes for OOME now and then:

#
# java.lang.OutOfMemoryError: Java heap space # -XX:OnOutOfMemoryError="kill -9 %p"
#   Executing /bin/sh -c "kill -9 16820"...

We have max heap size set to 22GB (-Xmx22528m) for each RS, and uses the G1GC (-XX:+UseG1GC).
To debug the problem we have turned on the jvm GC log.  The last few lines of the GC log before
each crash are always like
this:

2015-01-06T11:10:19.087+0000: 5035.720: [Full GC 7122M->5837M(21G),
0.8867660 secs]
   [Eden: 1024.0K(7278.0M)->0.0B(8139.0M) Survivors: 68.0M->0.0B Heap:
7122.7M(22.0G)->5837.2M(22.0G)]
 [Times: user=1.42 sys=0.00, real=0.89 secs]
2015-01-06T11:10:19.976+0000: 5036.608: [Full GC 5837M->5836M(21G),
0.6378260 secs]
   [Eden: 0.0B(8139.0M)->0.0B(8139.0M) Survivors: 0.0B->0.0B Heap:
5837.2M(22.0G)->5836.5M(22.0G)]
 [Times: user=0.93 sys=0.00, real=0.63 secs]

From the last lineI see the heap only occupies 5837MB, and the capacity is 22GB, so how can
the OOM happen? Or is my interpretation of the gc log wrong?

I read some articles and onlhy got some basic concept of G1GC. I've tried tools like GCViewer,
but none gives me useful explanation of the details of the GC log.


Regards,
Shuai
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