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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