Add a lifecycle interface for Hadoop components: namenodes, job clients, etc.
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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
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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