[jira] [Created] (MAPREDUCE-3886) add shutdown hook to shutdown a service; services to invoke

["Steve Loughran (Created) (JIRA)" <ji...@apache.org>]

add shutdown hook to shutdown a service; services to invoke
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                 Key: MAPREDUCE-3886
                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-3886
             Project: Hadoop Map/Reduce
          Issue Type: Improvement
          Components: mrv2
    Affects Versions: 0.23.0, 0.24.0
            Reporter: Steve Loughran


Currently the services (and their examples) don't handle KILL signals, because they don't register a shutdown hook. This means that they can't be shut down cleanly from a console without executing the service-specific commands.

Fix: add a class that takes a weak ref to a service and which registers a shutdown hook to call Service.stop on that service; catches and ignores any exceptions in the process. 

The abstract service should create an register a service on service start (unless told not to), and unregister it on service stop(). This would automatically give all services the desired behaviour. 

Composite services may not need this; it may be best to make registration an option that subclasses explicitly invoke in their service start methods, so only the key services get this feature.


coding: straightforward
testing: manual only; kill processes by hand and look at the logs

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