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From "Steve Loughran (JIRA)" <j...@apache.org>
Subject [jira] Updated: (HADOOP-3628) Add a lifecycle interface for Hadoop components: namenodes, job clients, etc.
Date Mon, 07 Jul 2008 14:23:31 GMT

     [ https://issues.apache.org/jira/browse/HADOOP-3628?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Steve Loughran updated HADOOP-3628:
-----------------------------------

    Attachment: hadoop-3628.patch

This patch is creates an abstract base class Service (in util) with a lifecycle, retrofits
to NameNode, DataNode, JobTracker and makes the changes to MiniDFS needed to get all the tests
to work (at least here). It is up to date with movements of the dfs code. which is why I'm
submitting today and not last friday.

-it also adds a standalone test that MiniDFS works. MiniDFS could be enhanced to share the
same base class lifecycle; this could be done while improving its startup/shutdown times,
which is the main reason the test cycle for hadoop is so long.

-it doesn't make any major attempts to fix problems with startup/shutdown of services that
have been noted in filed bugreps, except that service termination is now synchronized. Once
the patch is in other lifecycle issues with the nodes can be looked at.



> 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
>
>
> 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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