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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 Tue, 08 Jul 2008 16:54:31 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 updated patch is cleaner to subclass; I've been adapting what I had in terms of SmartFrog
support to deal with the new service base class. 

 innerInit, innerStart and innerTerminate methods for services to implement to do their work,
protected methods that will only get called if a state change is actually required (i.e. thread
safe state checking before entering/invoking). 

-a method onStateChange(ServiceState oldState, ServiceState newState) that is invoked when
a state change occurs, for subclasses to monitor/log. the base class just logs the event at
the info level.

There is no taskTracker support in there, that one is trickier. All the hadoop tests appear
to work; the SF tests are failing with in-process namenode not shutting down , which I believe
is a problem in my codebase, not this patch.

> 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, hadoop-3628.patch,
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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