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https://issues.apache.org/jira/browse/HBASE-9393?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15105939#comment-15105939
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Colin Patrick McCabe commented on HBASE-9393:
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Unfortunately, this is kind of a complex topic.
In HDFS, sockets for input streams are managed by the {{Peer}} class.
{{Peers}} can either be "owned" by {{DFSInputStream}} objects, or stored in the
{{PeerCache}}. The {{PeerCache}} already has appropriate timeouts and won't
keep open too many sockets. However, there is no limit to how long a
{{DFSInputStream}} could hold on to a {{Peer}}.
There are a few ways to minimize the number of open peers.
1. If HBase only ever called positional read (pread), the {{DFSInputStream}}
object would never own a {{Peer}}, so this issue would not arise.
2. If HBase called {{DFSInputStream#unbuffer}}, any open peers would be closed,
even though the stream would continue to be open.
3. If HDFS had a timeout for how long it would hold onto a {{Peer}}, that could
limit the number of open sockets.
Configuring HBase to periodically close open streams is not necessary; it's
strictly worse than option #2.
I believe there is an option do to #1 even right now. Can't HBase be
configured just to use pread and never read? #2 would require a code change to
HBase; #3 would require a code change to HDFS.
Are you running out of file descriptors? What's the user-visible problem here?
> Hbase does not closing a closed socket resulting in many CLOSE_WAIT
> --------------------------------------------------------------------
>
> Key: HBASE-9393
> URL: https://issues.apache.org/jira/browse/HBASE-9393
> Project: HBase
> Issue Type: Bug
> Affects Versions: 0.94.2, 0.98.0
> Environment: Centos 6.4 - 7 regionservers/datanodes, 8 TB per node,
> 7279 regions
> Reporter: Avi Zrachya
>
> HBase dose not close a dead connection with the datanode.
> This resulting in over 60K CLOSE_WAIT and at some point HBase can not connect
> to the datanode because too many mapped sockets from one host to another on
> the same port.
> The example below is with low CLOSE_WAIT count because we had to restart
> hbase to solve the porblem, later in time it will incease to 60-100K sockets
> on CLOSE_WAIT
> [root@hd2-region3 ~]# netstat -nap |grep CLOSE_WAIT |grep 21592 |wc -l
> 13156
> [root@hd2-region3 ~]# ps -ef |grep 21592
> root 17255 17219 0 12:26 pts/0 00:00:00 grep 21592
> hbase 21592 1 17 Aug29 ? 03:29:06
> /usr/java/jdk1.6.0_26/bin/java -XX:OnOutOfMemoryError=kill -9 %p -Xmx8000m
> -ea -XX:+UseConcMarkSweepGC -XX:+CMSIncrementalMode
> -Dhbase.log.dir=/var/log/hbase
> -Dhbase.log.file=hbase-hbase-regionserver-hd2-region3.swnet.corp.log ...
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