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https://issues.apache.org/jira/browse/HADOOP-12908?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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John Zhuge updated HADOOP-12908:
--------------------------------
    Attachment: HADOOP-12908-002.patch

Patch 002:
* Fix checkstyle and findbugs issues

> Make JvmPauseMonitor a singleton
> --------------------------------
>
>                 Key: HADOOP-12908
>                 URL: https://issues.apache.org/jira/browse/HADOOP-12908
>             Project: Hadoop Common
>          Issue Type: Improvement
>    Affects Versions: 2.7.2
>            Reporter: John Zhuge
>            Assignee: John Zhuge
>            Priority: Minor
>             Fix For: 2.8.0
>
>         Attachments: HADOOP-12908-001.patch, HADOOP-12908-002.patch
>
>
> Make JvmPauseMonitor a singleton just as JvmMetrics because there is no use 
> case to run multiple instances per JVM. No need for 
> {{TestMetrics$setPauseMonitor}} any more. Initialization code can be 
> simplified.
> For example, this code segment
> {noformat}
>     pauseMonitor = new JvmPauseMonitor();
>     addService(pauseMonitor);
>     jm.setPauseMonitor(pauseMonitor);
> {noformat}
> becomes
> {noformat}
>     addService(JvmPauseMonitor.INSTANCE);
> {noformat}
> And this code segment
> {noformat}
>       pauseMonitor = new JvmPauseMonitor();
>       pauseMonitor.init(config);
>       pauseMonitor.start();
>       metrics.getJvmMetrics().setPauseMonitor(pauseMonitor);
> {noformat}
> becomes
> {noformat}
>       pauseMonitor.INSTANCE.init(config);
>       pauseMonitor.INSTANCE.start();
> {noformat}



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