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Daryn Sharp commented on HDFS-7597: ----------------------------------- [~cnauroth] We can re-brand this as a more general improvement since it helps not only the DN but also the NN by reducing the per-connection UGI instances. I'm still not sure why HDFS-8855 is/was necessary because this internal patch solved the problem for us long ago. > DNs should not open new NN connections when webhdfs clients seek > ---------------------------------------------------------------- > > Key: HDFS-7597 > URL: https://issues.apache.org/jira/browse/HDFS-7597 > Project: Hadoop HDFS > Issue Type: Improvement > Components: webhdfs > Affects Versions: 2.0.0-alpha > Reporter: Daryn Sharp > Assignee: Daryn Sharp > Priority: Critical > Labels: BB2015-05-TBR > Attachments: HDFS-7597.patch, HDFS-7597.patch, HDFS-7597.patch > > > Webhdfs seeks involve closing the current connection, and reissuing a new > open request with the new offset. The RPC layer caches connections so the DN > keeps a lingering connection open to the NN. Connection caching is in part > based on UGI. Although the client used the same token for the new offset > request, the UGI is different which forces the DN to open another unnecessary > connection to the NN. > A job that performs many seeks will easily crash the NN due to fd exhaustion. -- This message was sent by Atlassian JIRA (v6.3.4#6332)