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Date: Wed, 15 Feb 2017 06:59:41 +0000 (UTC)
From: "Brahma Reddy Battula (JIRA)" <jira@apache.org>
To: hdfs-issues@hadoop.apache.org
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Subject: [jira] [Comment Edited] (HDFS-6804) race condition between
 transferring block and appending block causes "Unexpected checksum mismatch
 exception"
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archived-at: Wed, 15 Feb 2017 06:59:59 -0000


    [ https://issues.apache.org/jira/browse/HDFS-6804?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15867058#comment-15867058 ] 

Brahma Reddy Battula edited comment on HDFS-6804 at 2/15/17 6:58 AM:
---------------------------------------------------------------------

Attaching the reproduce patch for this scenario..


was (Author: brahmareddy):
Attaching the reproduce scenario for this scenario..

> race condition between transferring block and appending block causes "Unexpected checksum mismatch exception" 
> --------------------------------------------------------------------------------------------------------------
>
>                 Key: HDFS-6804
>                 URL: https://issues.apache.org/jira/browse/HDFS-6804
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: datanode
>    Affects Versions: 2.2.0
>            Reporter: Gordon Wang
>            Assignee: Wei-Chiu Chuang
>         Attachments: Testcase_append_transfer_block.patch
>
>
> We found some error log in the datanode. like this
> {noformat}
> 2014-07-22 01:49:51,338 INFO org.apache.hadoop.hdfs.server.datanode.DataNode: Ex
> ception for BP-2072804351-192.168.2.104-1406008383435:blk_1073741997_9248
> java.io.IOException: Terminating due to a checksum error.java.io.IOException: Unexpected checksum mismatch while writing BP-2072804351-192.168.2.104-1406008383435:blk_1073741997_9248 from /192.168.2.101:39495
>         at org.apache.hadoop.hdfs.server.datanode.BlockReceiver.receivePacket(BlockReceiver.java:536)
>         at org.apache.hadoop.hdfs.server.datanode.BlockReceiver.receiveBlock(BlockReceiver.java:703)
>         at org.apache.hadoop.hdfs.server.datanode.DataXceiver.writeBlock(DataXceiver.java:575)
>         at org.apache.hadoop.hdfs.protocol.datatransfer.Receiver.opWriteBlock(Receiver.java:115)
>         at org.apache.hadoop.hdfs.protocol.datatransfer.Receiver.processOp(Receiver.java:68)
>         at org.apache.hadoop.hdfs.server.datanode.DataXceiver.run(DataXceiver.java:221)
>         at java.lang.Thread.run(Thread.java:744)
> {noformat}
> While on the source datanode, the log says the block is transmitted.
> {noformat}
> 2014-07-22 01:49:50,805 INFO org.apache.hadoop.hdfs.server.datanode.DataNode: Da
> taTransfer: Transmitted BP-2072804351-192.168.2.104-1406008383435:blk_1073741997
> _9248 (numBytes=16188152) to /192.168.2.103:50010
> {noformat}
> When the destination datanode gets the checksum mismatch, it reports bad block to NameNode and NameNode marks the replica on the source datanode as corrupt. But actually, the replica on the source datanode is valid. Because the replica can pass the checksum verification.
> In all, the replica on the source data is wrongly marked as corrupted.


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