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Date: Mon, 9 Nov 2009 17:27:33 +0000 (UTC)
From: "Stu Hood (JIRA)" <jira@apache.org>
To: hdfs-issues@hadoop.apache.org
Subject: [jira] Commented: (HDFS-326) Add a lifecycle interface for Hadoop
 components: namenodes, job clients, etc.
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    [ https://issues.apache.org/jira/browse/HDFS-326?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12775030#action_12775030 ] 

Stu Hood commented on HDFS-326:
-------------------------------

Hey Steve, what is the status of this issue? Have you decided to move forward with the "separate issues per component" approach? Integrating lifecycle into the different daemons is very attractive, since as you pointed out, it allows for ZooKeeper management.

> Add a lifecycle interface for Hadoop components: namenodes, job clients, etc.
> -----------------------------------------------------------------------------
>
>                 Key: HDFS-326
>                 URL: https://issues.apache.org/jira/browse/HDFS-326
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>            Reporter: Steve Loughran
>            Assignee: Steve Loughran
>         Attachments: AbstractHadoopComponent.java, HADOOP-3628-18.patch, HADOOP-3628-19.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-3628.patch, hadoop-lifecycle-tomw.sxw, hadoop-lifecycle.pdf, 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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