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From "GAO Rui (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HDFS-10710) In BlockManager#rescanPostponedMisreplicatedBlocks(), start and end block counts should be get with the protect with lock
Date Mon, 01 Aug 2016 09:37:20 GMT
GAO Rui created HDFS-10710:
------------------------------

             Summary: In BlockManager#rescanPostponedMisreplicatedBlocks(), start and end
block counts should be get with the protect with lock
                 Key: HDFS-10710
                 URL: https://issues.apache.org/jira/browse/HDFS-10710
             Project: Hadoop HDFS
          Issue Type: Bug
          Components: namenode
            Reporter: GAO Rui
            Assignee: GAO Rui


In BlockManager#rescanPostponedMisreplicatedBlocks(), start and end block counts should be
get with the protect with lock. Or, log records like "-1 blocks are removed" which indicate
minus blocks are removed could be generated. 

For example, following scenario:
1. thread1 run {{long startPostponedMisReplicatedBlocksCount = getPostponedMisreplicatedBlocksCount();}}
currently  startPostponedMisReplicatedBlocksCount get the value 20.
2. before thread1 run {{namesystem.writeLock();}} , thread2 increment postponedMisreplicatedBlocksCount
by 1, so postponedMisreplicatedBlocksCount is 21 now.
3. thread1 end the iteration, but no postponed block is removed, so after run {{long endPostponedMisReplicatedBlocksCount
= getPostponedMisreplicatedBlocksCount();}}, endPostponedMisReplicatedBlocksCount get the
value of 21.
4. thread 1 generate the log:
```
LOG.info("Rescan of postponedMisreplicatedBlocks completed in " +
(Time.monotonicNow() - startTimeRescanPostponedMisReplicatedBlocks) +
" msecs. " + endPostponedMisReplicatedBlocksCount +
" blocks are left. " + (startPostponedMisReplicatedBlocksCount -
endPostponedMisReplicatedBlocksCount) + " blocks are removed.");
```
Then, we'll get the log record like "-1 blocks are removed."



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