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https://issues.apache.org/jira/browse/HADOOP-3628?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12611679#action_12611679
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Steve Loughran commented on HADOOP-3628:
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on the subject of trackers, is there any reason why JobTracker.stopTracker
doesnt close its filesystem; doesn't call fs.close()?
If you find the usages of stopTracker() , all but one of them call
jt.fs.close() first, which means they assume that jt.fs != null, and that
closing doesn't cause problems. The only case where fs.close() isnt invokes is
in JobTracker.addHostToNodeMapping(), and the method is unusual in that it is
logging at FATAL and calls System.exit() if it cannot stop the tracker.
I propose always closing the filesystem when the tracker is stopped (if
needed), and removing those lines in the code where it is externally stopped.
> Add a lifecycle interface for Hadoop components: namenodes, job clients, etc.
> -----------------------------------------------------------------------------
>
> Key: HADOOP-3628
> URL: https://issues.apache.org/jira/browse/HADOOP-3628
> Project: Hadoop Core
> Issue Type: Improvement
> Components: dfs, mapred
> Affects Versions: 0.19.0
> Reporter: Steve Loughran
> Assignee: Steve Loughran
> Attachments: AbstractHadoopComponent.java, hadoop-3628.patch,
> hadoop-3628.patch
>
>
> I'd like to propose we have a standard interface for hadoop components, the
> things that get started or stopped when you bring up a namenode. currently,
> some of these classes have a stop() or shutdown() method, with no standard
> name/interface, but no way of seeing if they are live, checking their health
> of shutting them down reliably. Indeed, there is a tendency for the spawned
> threads to not want to die; to require the entire process to be killed to
> stop the workers.
> Having a standard interface would make it easier for
> * management tools to manage the different things
> * monitoring the state of things
> * subclassing
> The latter is interesting as right now TaskTracker and JobTracker start up
> threads in their constructor; that's very dangerous as subclasses may have
> their methods called before they are full initialised. Adding this interface
> would be the right time to clean up the startup process so that subclassing
> is less risky.
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