Tao Zhang created HDFS-12906:
--------------------------------

             Summary: hedged point read in DFSInputStream sends only 1 hedge 
read request
                 Key: HDFS-12906
                 URL: https://issues.apache.org/jira/browse/HDFS-12906
             Project: Hadoop HDFS
          Issue Type: Bug
          Components: hdfs-client
            Reporter: Tao Zhang
            Assignee: Tao Zhang


Hedged point read is handled in DFSInputStream.hedgedFetchBlockByteRange(). It 
calls "getFirstToComplete()" to get the 1st returned result after sending out 
hedge read requests. But since "getFirstToComplete()" uses 
"CompletionService.take()" which is a endlessly blocking operation. It will 
wait for 1 result after sending only 1 hedge read request.

It could be changed to wait for a specific timeout (instead of infinite 
timeout) and starting another hedge read request. 



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