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https://issues.apache.org/jira/browse/HDFS-9242?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14984482#comment-14984482
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Haohui Mai commented on HDFS-9242:
----------------------------------
bq. I think the warning is false positive. We can write a filter rule in the
dev-support/findbugsExcludeFile.xml file.
Findbug is right. The code is simply broken. It is possible to have multiple
instances of cache map.
bq. A correct way to fix is to make ugiCache volatile. Could you update it?
Fixing it with volatile is a bad idea as it bars many compiler optimization.
The suggested pattern is to do it through static initializer blocks, where the
synchronization is properly handled.
> Fix Findbugs warning from webhdfs.DataNodeUGIProvider.ugiCache
> ---------------------------------------------------------------
>
> Key: HDFS-9242
> URL: https://issues.apache.org/jira/browse/HDFS-9242
> Project: Hadoop HDFS
> Issue Type: Bug
> Reporter: Xiaoyu Yao
> Assignee: Brahma Reddy Battula
> Attachments: HDFS-9242.patch
>
>
> This was introduced by HDFS-8855 and pre-patch warning can be found at
> https://builds.apache.org/job/PreCommit-HDFS-Build/12975/artifact/patchprocess/trunkFindbugsWarningshadoop-hdfs.html#DC_DOUBLECHECK
> {code}
> Code Warning
> DC Possible doublecheck on
> org.apache.hadoop.hdfs.server.datanode.web.webhdfs.DataNodeUGIProvider.ugiCache
> in new
> org.apache.hadoop.hdfs.server.datanode.web.webhdfs.DataNodeUGIProvider(ParameterParser,
> Configuration)
> Bug type DC_DOUBLECHECK (click for details)
> In class
> org.apache.hadoop.hdfs.server.datanode.web.webhdfs.DataNodeUGIProvider
> In method new
> org.apache.hadoop.hdfs.server.datanode.web.webhdfs.DataNodeUGIProvider(ParameterParser,
> Configuration)
> On field
> org.apache.hadoop.hdfs.server.datanode.web.webhdfs.DataNodeUGIProvider.ugiCache
> At DataNodeUGIProvider.java:[lines 49-51]
> {code}
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