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https://issues.apache.org/jira/browse/HDFS-5970?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13906672#comment-13906672
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Yongjun Zhang commented on HDFS-5970:
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Hi Iunping,
Thanks for your encouraging words!
I need to mention that this bug is related to HDFS-5939 that I'm working on. I
tried to address HDFS-5939 by adding "return null"
from within the chooseRandom mehtod. Thanks to [~wheat9] who suggested that we
need to file this JIRA for callers of this method to
be aware of that the method could return null when reviewing my HDFS-5939 fix.
While we are still discussing the best solution for
HDFS-5939, it's likely we will replace the "return null" I added with throwing
an exception.
Prior to my change, the method chooseRandom already has a piece of code that
returns null under certain condition, So this JIRA is
still valid in that sense. However, we haven't got any report of null value
returned from that piece of code yet, probably we can keep
this JIRA open until we have a real case.
Thanks.
> callers of NetworkTopology's chooseRandom method to expect null return value
> ----------------------------------------------------------------------------
>
> Key: HDFS-5970
> URL: https://issues.apache.org/jira/browse/HDFS-5970
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: namenode
> Affects Versions: 3.0.0
> Reporter: Yongjun Zhang
>
> Class NetworkTopology's method
> public Node chooseRandom(String scope)
> calls
> private Node chooseRandom(String scope, String excludedScope)
> which may return null value.
> Callers of this method such as BlockPlacementPolicyDefault etc need to be
> aware that.
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