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https://issues.apache.org/jira/browse/HDFS-12415?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16202341#comment-16202341
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Chen Liang commented on HDFS-12415:
-----------------------------------
I looked in this a little bit too. What was happening seems to be that
{{SCMCommonPolicy#chooseDatanodes}} calls
{{nodeManager.getNodes(OzoneProtos.NodeState.HEALTHY);}}, but the returned list
contains a {{null}} datanode id entry. So the {{hasEnoughSpace(d,
sizeRequired)}} call on the null d will fail with NPE. And the returned list
with a null entry is returned by {{SCMNodeManager#getNodes}}, where seems there
is some datanode id in {{healthyNodes}} but not present in {{nodes}} map.
I don't see how could a datanode id be present in {{healthyNodes}} but not in
{{nodes}}, because the first thing of register is to always add that datanode
to {{nodes}}, before {{healthyNodes}}. I can only think of the issue being just
like [~msingh] mentioned, that it is probably due to some unexpected race
condition behaviour when two register calls happen and change the HashMap
{{nodes}} at the same time. So I would +1 on Mukul's change. Additionally, I
ran {{TestXceiverClientManager}} several ten times with v005 patch applied. The
test did not fail.
> Ozone: TestXceiverClientManager and TestAllocateContainer occasionally fails
> ----------------------------------------------------------------------------
>
> Key: HDFS-12415
> URL: https://issues.apache.org/jira/browse/HDFS-12415
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Affects Versions: HDFS-7240
> Reporter: Weiwei Yang
> Assignee: Weiwei Yang
> Attachments: HDFS-12415-HDFS-7240.001.patch,
> HDFS-12415-HDFS-7240.002.patch, HDFS-12415-HDFS-7240.003.patch,
> HDFS-12415-HDFS-7240.004.patch, HDFS-12415-HDFS-7240.005.patch
>
>
> TestXceiverClientManager seems to be occasionally failing in some jenkins
> jobs,
> {noformat}
> java.lang.NullPointerException
> at
> org.apache.hadoop.ozone.scm.node.SCMNodeManager.getNodeStat(SCMNodeManager.java:828)
> at
> org.apache.hadoop.ozone.scm.container.placement.algorithms.SCMCommonPolicy.hasEnoughSpace(SCMCommonPolicy.java:147)
> at
> org.apache.hadoop.ozone.scm.container.placement.algorithms.SCMCommonPolicy.lambda$chooseDatanodes$0(SCMCommonPolicy.java:125)
> {noformat}
> see more from [this
> report|https://builds.apache.org/job/PreCommit-HDFS-Build/21065/testReport/]
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