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https://issues.apache.org/jira/browse/HIVE-26677?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17633421#comment-17633421
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Chris Nauroth commented on HIVE-26677:
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[~szita] , thank you!
> Constrain available processors to Jetty during test runs to prevent thread
> exhaustion.
> --------------------------------------------------------------------------------------
>
> Key: HIVE-26677
> URL: https://issues.apache.org/jira/browse/HIVE-26677
> Project: Hive
> Issue Type: Test
> Components: Test
> Reporter: Chris Nauroth
> Assignee: Chris Nauroth
> Priority: Major
> Labels: pull-request-available
> Fix For: 4.0.0
>
> Time Spent: 0.5h
> Remaining Estimate: 0h
>
> As described during a [release candidate
> vote|https://lists.apache.org/thread/8qjf7x9t9v09d79hlzh712ls4zthdwrh]:
> HIVE-24484 introduced a change to limit {{hive.server2.webui.max.threads}} to
> 4. Jetty enforces thread leasing to warn or abort if there aren't enough
> threads available [1]. During startup, it attempts to lease a thread per NIO
> selector [2]. By default, the number of NIO selectors to use is determined
> based on available CPUs [3]. This is mostly a passthrough to
> {{Runtime.availableProcessors()}} [4]. In my case, running on a machine with
> 16 CPUs, this ended up creating more than 4 selectors, therefore requiring
> more than 4 threads and violating the lease check. I was able to work around
> this by passing the {{JETTY_AVAILABLE_PROCESSORS}} system property to
> constrain the number of CPUs available to Jetty.
> Since we are intentionally constraining the pool to 4 threads during itests,
> let's also limit {{JETTY_AVAILABLE_PROCESSORS}} in {{maven.test.jvm.args}} of
> the root pom.xml, so that others don't run into this problem later.
> [1]
> https://github.com/eclipse/jetty.project/blob/jetty-9.4.40.v20210413/jetty-util/src/main/java/org/eclipse/jetty/util/thread/ThreadPoolBudget.java#L165
> [2]
> https://github.com/eclipse/jetty.project/blob/jetty-9.4.40.v20210413/jetty-io/src/main/java/org/eclipse/jetty/io/SelectorManager.java#L255
> [3]
> https://github.com/eclipse/jetty.project/blob/jetty-9.4.40.v20210413/jetty-io/src/main/java/org/eclipse/jetty/io/SelectorManager.java#L79
> [4]
> https://github.com/eclipse/jetty.project/blob/jetty-9.4.40.v20210413/jetty-util/src/main/java/org/eclipse/jetty/util/ProcessorUtils.java#L45
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