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From "Binglin Chang (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HDFS-4273) Problem in DFSInputStream read retry logic may cause early failure
Date Wed, 05 Dec 2012 15:04:58 GMT
Binglin Chang created HDFS-4273:
-----------------------------------

             Summary: Problem in DFSInputStream read retry logic may cause early failure
                 Key: HDFS-4273
                 URL: https://issues.apache.org/jira/browse/HDFS-4273
             Project: Hadoop HDFS
          Issue Type: Bug
            Reporter: Binglin Chang
            Assignee: Binglin Chang
            Priority: Minor


Assume the following call logic
{noformat} 
readWithStrategy()
  -> blockSeekTo()
  -> readBuffer()
     -> reader.doRead()
     -> seekToNewSource() add currentNode to deadnode, wish to get a different datanode
        -> blockSeekTo()
           -> chooseDataNode()
              -> block missing, clear deadNodes and pick the currentNode again
        seekToNewSource() return false
     readBuffer() re-throw the exception quit loop
readWithStrategy() got the exception,  and may fail the read call before tried MaxBlockAcquireFailures.
{noformat} 
some issues of the logic:
1. seekToNewSource() logic is broken because it may clear deadNodes in the middle.
2. the variable "int retries=2" in readWithStrategy seems have conflict with MaxBlockAcquireFailures,
should it be removed?


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