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From "Masatake Iwasaki (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HDFS-4273) Fix some issue in DFSInputstream
Date Fri, 22 May 2015 07:49:19 GMT

     [ https://issues.apache.org/jira/browse/HDFS-4273?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Masatake Iwasaki updated HDFS-4273:
-----------------------------------
          Resolution: Won't Fix
    Target Version/s: 2.0.3-alpha, 3.0.0  (was: 3.0.0, 2.0.3-alpha)
              Status: Resolved  (was: Patch Available)

I looked into tests added by .v8 patch.

{{TestDFSClientRetries#testDFSInputStreamReadRetryTime}} added by .v8 patch. The test expects
client to always retry up to maxBlockAcquireFailures but it is not true. Client does not retry
to same node on ChecksumException. {{seekToNewSource}} returning 0 means there is no more
possible datanodes and it is right to give up even if retry count (failures) does not reache
to max.

{{testSeekToNewSourcePastFileSize}} and {{testNegativeSeekToNewSource}} added to {{TestSeekBug}}
calls {{FSDataInpuStream#seekToNewSource}} just after opening file. This causes NullPointerException
because currentNode is not set in DFSInputstream. Tests passed after fixing this.

I close this issue as Won't fix.


> Fix some issue in DFSInputstream
> --------------------------------
>
>                 Key: HDFS-4273
>                 URL: https://issues.apache.org/jira/browse/HDFS-4273
>             Project: Hadoop HDFS
>          Issue Type: Bug
>    Affects Versions: 2.0.2-alpha
>            Reporter: Binglin Chang
>            Assignee: Binglin Chang
>            Priority: Minor
>         Attachments: HDFS-4273-v2.patch, HDFS-4273.patch, HDFS-4273.v3.patch, HDFS-4273.v4.patch,
HDFS-4273.v5.patch, HDFS-4273.v6.patch, HDFS-4273.v7.patch, HDFS-4273.v8.patch, TestDFSInputStream.java
>
>
> Following issues in DFSInputStream are addressed in this jira:
> 1. read may not retry enough in some cases cause early failure
> 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} 
> 2. In multi-threaded scenario(like hbase), DFSInputStream.failures has race condition,
it is cleared to 0 when it is still used by other thread. So it is possible that  some read
thread may never quit. Change failures to local variable solve this issue.
> 3. If local datanode is added to deadNodes, it will not be removed from deadNodes if
DN is back alive. We need a way to remove local datanode from deadNodes when the local datanode
is become live.



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