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https://issues.apache.org/jira/browse/YARN-1183?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13802109#comment-13802109
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Karthik Kambatla commented on YARN-1183:
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In the past, we have run into cases where the default concurrency level led to
high memory usage. MAPREDUCE-5368 is one example.
While I do agree that it might not lead to big differences for something
"short-lived" like MiniYARNCluster, I think it is good practice to use a
smaller value when we know the number of concurrent accesses is low.
> MiniYARNCluster shutdown takes several minutes intermittently
> -------------------------------------------------------------
>
> Key: YARN-1183
> URL: https://issues.apache.org/jira/browse/YARN-1183
> Project: Hadoop YARN
> Issue Type: Bug
> Reporter: Andrey Klochkov
> Assignee: Andrey Klochkov
> Attachments: YARN-1183--n2.patch, YARN-1183--n3.patch,
> YARN-1183--n4.patch, YARN-1183.patch
>
>
> As described in MAPREDUCE-5501 sometimes M/R tests leave MRAppMaster java
> processes living for several minutes after successful completion of the
> corresponding test. There is a concurrency issue in MiniYARNCluster shutdown
> logic which leads to this. Sometimes RM stops before an app master sends it's
> last report, and then the app master keeps retrying for >6 minutes. In some
> cases it leads to failures in subsequent tests, and it affects performance of
> tests as app masters eat resources.
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