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https://issues.apache.org/jira/browse/HDFS-4351?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13542499#comment-13542499
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Jing Zhao commented on HDFS-4351:
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bq. Regarding numOfReplicas, my reading is that it's the # of additional nodes
that need to be added to the results list.
Yes. So I think the new numOfReplicas passed into the chooseTarget when a
NotEnoughReplicasException is thrown should be calculated based on the change
of the number of nodes in the results list. So it can be either
"oldNumOfReplicas - (number of new nodes in results)" or "oldNumOfReplicas +
(initial number of nodes in results) - (current number of nodes in results)".
> Fix BlockPlacementPolicyDefault#chooseTarget when avoiding stale nodes
> ----------------------------------------------------------------------
>
> Key: HDFS-4351
> URL: https://issues.apache.org/jira/browse/HDFS-4351
> Project: Hadoop HDFS
> Issue Type: Bug
> Affects Versions: 3.0.0
> Reporter: Andrew Wang
> Assignee: Andrew Wang
> Attachments: hdfs-4351-2.patch, hdfs-4351-3.patch, hdfs-4351.patch
>
>
> There's a bug in {{BlockPlacementPolicyDefault#chooseTarget}} with stale node
> avoidance enabled (HDFS-3912). If a NotEnoughReplicasException is thrown in
> the call to {{chooseRandom()}}, {{numOfReplicas}} is not updated together
> with the partial result in {{result}} since it is pass by value. The retry
> call to {{chooseTarget}} then uses this incorrect value.
> This can be seen if you enable stale node detection for
> {{TestReplicationPolicy#testChooseTargetWithMoreThanAvaiableNodes()}}.
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