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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:
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Status: In Progress (was: Patch Available)
Thanks [~djp].
I am glad you prefer the singleton approach among the following 3 choices:
* HADOOP-12908: Add option {{jvm.pause.monitor.enabled}} to turn on/off the
monitor thread
* HADOOP-12946: Ensure at most one monitor thread when there are multiple
JvmPauseMonitor instances
* HADOOP-12908: Make JvmPauseMonitor a singleton thus only one monitor thread
is running. Multiple services can share the singleton in mini clusters. Add a
reusable class {{AbstractSharedService}}.
Let me also explore Dependency Injection (DI) a bit because I'd prefer DI over
Singleton. However, considering {{JvmMetrics}} is already a singleton, we might
have to live with Singleton.
> 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
> Attachments: HADOOP-12908-001.patch, HADOOP-12908-002.patch,
> HADOOP-12908-003.patch
>
>
> Make JvmPauseMonitor a singleton just as JvmMetrics because there is no use
> case to run multiple instances per JVM. {{TestMetrics$setPauseMonitor}}
> becomes obsolete. Initialization code for various components can be
> simplified.
> For example, this code segment
> {code}
> pauseMonitor = new JvmPauseMonitor();
> addService(pauseMonitor);
> jm.setPauseMonitor(pauseMonitor);
> {code}
> can be replaced with
> {code}
> addService(JvmPauseMonitor.getInstance());
> {code}
> And this code segment
> {code}
> pauseMonitor = new JvmPauseMonitor();
> pauseMonitor.init(config);
> pauseMonitor.start();
> metrics.getJvmMetrics().setPauseMonitor(pauseMonitor);
> {code}
> can be replaced with
> {code}
> pauseMonitor = JvmPauseMonitor.getInstance();
> pauseMonitor.init(config);
> pauseMonitor.start();
> {code}
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