[jira] Commented: (HADOOP-3628) Add a lifecycle interface for Hadoop components: namenodes, job clients, etc.

["Steve Loughran (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HADOOP-3628?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12711220#action_12711220 ] 

Steve Loughran commented on HADOOP-3628:
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For anyone wondering what the status of this is, I stopped synchronizing my code just before apachecon, to get some things working (and an RPM out the door), and took a vacation. Now I'm catching up -it turns out the easiest approach is to diff the state between my branch and the original code and the time of the branch, then semi-manually apply those changes to SVN head of trunk, first the filesystem then the job tracker.



> 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: 0.20.0
>            Reporter: Steve Loughran
>            Assignee: Steve Loughran
>             Fix For: 0.21.0
>
>         Attachments: AbstractHadoopComponent.java, hadoop-3628.patch, hadoop-3628.patch, hadoop-3628.patch, hadoop-3628.patch, hadoop-3628.patch, hadoop-3628.patch, hadoop-3628.patch, hadoop-3628.patch, hadoop-3628.patch, hadoop-3628.patch, hadoop-3628.patch, hadoop-3628.patch, hadoop-3628.patch, hadoop-3628.patch, hadoop-3628.patch, hadoop-3628.patch, hadoop-3628.patch, hadoop-lifecycle-tomw.sxw, hadoop-lifecycle.pdf, hadoop-lifecycle.sxw
>
>
> 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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