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https://issues.apache.org/jira/browse/HDFS-326?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12755591#action_12755591
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Hong Tang commented on HDFS-326:
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bq. 2. I'm worried about the problem of what happens if you try to stop a
service while it is starting up. Some of the services do take a while to start,
and you should have the right to interrupt something like a JobTracker and tell
it to go away.
Without look at the patch, I am a bit confusion by "... do take a while to
start", do you mean the service will take a while in STARTING or in
INITIALIZING? I think in general a component should do the minimum to set up
itself to a consistent state in STARTING stage and defer length initialization
in the INITIALIZING stage. And we would allow STARTING to run through
uninterrupted but support aborting the initialization.
> 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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