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From "Pete Wyckoff (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-3628) Add a lifecycle interface for Hadoop components: namenodes, job clients, etc.
Date Mon, 08 Sep 2008 21:39:44 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-3628?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12629303#action_12629303
] 

Pete Wyckoff commented on HADOOP-3628:
--------------------------------------

I opened: https://issues.apache.org/jira/browse/HADOOP-3969, to implement a mechanism for
instantiating a class that exposes the public service apis to external tools.

{code}
package org.apache.hadoop.util;

public interface ExposeServiceAPIs {

   /**
   * @param service - the service whose APIs are to be exposed
  * @param  serviceName - a symbolic name for the service
  * @param configuration - the hadoop configuration object
 **/
  public void initialize(Service service, String serviceName, Configuration conf) throws IOException,
  public boolean start();
  public boolean stop();
} ;

{code}

The reference implementation will be REST which I'm working on now, but will obviously need
some hooks in the service class itself.

> 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, 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.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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