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From "Xiao Chen (JIRA)" <j...@apache.org>
Subject [jira] [Comment Edited] (HDFS-13539) DFSInputStream NPE when reportCheckSumFailure
Date Wed, 09 May 2018 17:56:00 GMT

    [ https://issues.apache.org/jira/browse/HDFS-13539?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16469077#comment-16469077
] 

Xiao Chen edited comment on HDFS-13539 at 5/9/18 5:55 PM:
----------------------------------------------------------

Failed tests does not look related.

For clarity:
- The synchronized changes are only for following best practice, I don't see any real issues
from there that could cause the NPE
- Existing checks guards {{pos}} and {{blockEnd}} pretty well, to make sure {{blockSeekTo}}
can return a valid {{currentLocatedBlock}}. This is presumably why the NPE is only seen on
striped streams. But regardless, having the possibility of NPE will mask the original exception,
so this patch proposed to improve on that end.


was (Author: xiaochen):
Failed tests does not look related.
The synchronized changes are only for following best practice, I don't see any real issues
from there that could cause the NPE

> DFSInputStream NPE when reportCheckSumFailure
> ---------------------------------------------
>
>                 Key: HDFS-13539
>                 URL: https://issues.apache.org/jira/browse/HDFS-13539
>             Project: Hadoop HDFS
>          Issue Type: Bug
>            Reporter: Xiao Chen
>            Assignee: Xiao Chen
>            Priority: Major
>         Attachments: HDFS-13539.01.patch
>
>
> We have seem the following exception with DFSStripedInputStream.
> {noformat}
> readDirect: FSDataInputStream#read error:
> NullPointerException: java.lang.NullPointerException
>         at org.apache.hadoop.hdfs.DFSStripedInputStream.readWithStrategy(DFSStripedInputStream.java:402)
>         at org.apache.hadoop.hdfs.DFSInputStream.read(DFSInputStream.java:831)
>         at org.apache.hadoop.fs.FSDataInputStream.read(FSDataInputStream.java:147)
> {noformat}
> Line 402 is {{reportCheckSumFailure}}, and {{currentLocatedBlock}} is the only possible
null object. (Because {{currentLocatedBlock.getLocations()}} cannot be null - {{LocatedBlock}}
constructor checks {{locs}} and would assign a {{EMPTY_LOCS}} if it's null)
> Original exception is masked by the NPE.



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