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From "Colin Patrick McCabe (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HDFS-6695) Investigate using Java 7's nonblocking file I/O in BlockReaderLocal to implement read timeouts
Date Wed, 16 Jul 2014 18:38:05 GMT
Colin Patrick McCabe created HDFS-6695:
------------------------------------------

             Summary: Investigate using Java 7's nonblocking file I/O in BlockReaderLocal
to implement read timeouts
                 Key: HDFS-6695
                 URL: https://issues.apache.org/jira/browse/HDFS-6695
             Project: Hadoop HDFS
          Issue Type: Improvement
            Reporter: Colin Patrick McCabe


In BlockReaderLocal, the "read" system call could block for a long time if the disk drive
is having problems, or there is a huge amount of I/O contention.  This might cause poor latency
performance.

In the remote block readers, we have implemented a read timeout, but we don't have one for
the local block reader, since {{FileChannel#read}} doesn't support this.  

Once we move to JDK 7, we should investigate the {{java.nio.file}} nonblocking file I/O package
to see if it could be used to implement read timeouts.



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