[
https://issues.apache.org/jira/browse/HDFS-12487?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17111917#comment-17111917
]
pengWei Dou commented on HDFS-12487:
------------------------------------
hi，[~liumihust]， when i used [^HDFS-12487.003.patch] ， i find the following
code in DiskBalancer#getBlockToCopy,
{code:java}
// if (block != null) {
...
} else {
}
{code}
so, why do null check in your patch, can you explain is? thanks!
> FsDatasetSpi.isValidBlock() lacks null pointer check inside and neither do
> the callers
> --------------------------------------------------------------------------------------
>
> Key: HDFS-12487
> URL: https://issues.apache.org/jira/browse/HDFS-12487
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: balancer & mover, diskbalancer
> Affects Versions: 3.0.0
> Environment: CentOS 6.8 x64
> CPU:4 core
> Memory:16GB
> Hadoop: Release 3.0.0-alpha4
> Reporter: liumi
> Assignee: liumi
> Priority: Major
> Fix For: 3.3.0, 3.2.1, 3.1.3
>
> Attachments: HDFS-12487.002.patch, HDFS-12487.003.patch
>
> Original Estimate: 0h
> Remaining Estimate: 0h
>
> BlockIteratorImpl.nextBlock() will look for the blocks in the source volume,
> if there are no blocks any more, it will return null up to
> DiskBalancer.getBlockToCopy(). However, the DiskBalancer.getBlockToCopy()
> will check whether it's a valid block.
> When I look into the FsDatasetSpi.isValidBlock(), I find that it doesn't
> check the null pointer! In fact, we firstly need to check whether it's null
> or not, or exception will occur.
> This bug is hard to find, because the DiskBalancer hardly copy all the data
> of one volume to others. Even if some times we may copy all the data of one
> volume to other volumes, when the bug occurs, the copy process has already
> done.
> However, when we try to copy all the data of two or more volumes to other
> volumes in more than one step, the thread will be shut down, which is caused
> by the bug above.
> The bug can fixed by two ways:
> 1)Before the call of FsDatasetSpi.isValidBlock(), we check the null pointer
> 2)Check the null pointer inside the implementation of
> FsDatasetSpi.isValidBlock()
--
This message was sent by Atlassian Jira
(v8.3.4#803005)
---------------------------------------------------------------------
To unsubscribe, e-mail: [email protected]
For additional commands, e-mail: [email protected]
