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From "Steve Loughran (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-3628) Add a lifecycle interface for Hadoop components: namenodes, job clients, etc.
Date Thu, 26 Jun 2008 14:43:45 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-3628?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12608454#action_12608454
] 

Steve Loughran commented on HADOOP-3628:
----------------------------------------

Daemon is taken in utils, with a thread that has setDaemon.true; Service would work.

I'm running the tests on a prototype implementation; namenode and datanode have been reparented
by Service; let's see what goes wrong. What worries me most is termination(); in my own tests
of the existing code I've found that some things dont shut down very well and ports stay open
until the process is killed...

> 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
>
>
> 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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