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From Sreekanth Ramakrishnan <sreekanth.ramakrish...@inmobi.com>
Subject Max DataXceiver Exceeded Logs in DataNode log files
Date Tue, 02 Apr 2013 08:49:25 GMT
Hi All,

We are currently running Hadoop 0.20.X version of hadoop cluster in our environment. We have
been recently observing slow down of datanodes and DFSClient times out. Looking at the logs
in the data nodes we noticed that there were quite a bit of Max DataXceiver exceeded exception
messages of following format.

java.io.IOException: xceiverCount 4114 exceeds the limit of concurrent xcievers
4096

Our cluster configuration allows max of 4096 DataXceiver. And due to this exception our  dfs
clients are getting blocked slowing down DFS Performance from Client prespective.

When JStack of the datanode process was checked, it showed that out of 4166 Active threads
in the JVM 1336 threads were of DataXceiver. 2796 threads were PacketResponder threads. Shouldn't
DataNode spawn 2760 more DataXceiver before throwing the IOException?

Also looking at the code, it seems that we are not setting different thread group for BlockReceiver
which causes the thread pool to be split between BlockReceiver and DataXceiver. Is this intentional?

Are there are any work arounds to see to that max allocation of threads are allocated to DataXceiver?

Or should I go ahead and file a JIRA regarding this issue? 





Sreekanth Ramakrishnan


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