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From "Steve Loughran (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-9933) Augment Service model to support starting stopped services
Date Thu, 05 Sep 2013 10:53:51 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-9933?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13758976#comment-13758976
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Steve Loughran commented on HADOOP-9933:
----------------------------------------

I'm not sure (based on past experience) that restarting arbitrary services works reliably
-it often turns out that they don't ever shut down as cleanly as they think (leaked threads,
memory, file handles). Then theres the special case of a service that failed during init/startup
(which we don't treat as a unique termination state, but we do record with the exception that
triggered the failure, so the fact a failure occurred can be inferred.

Is there a way that we could avoid this -or add some marker interface to indicate that the
service considers itself restartable, have some activate/passivate methods that can suspend
some aspects of the system? 

There's always the option of having a ready-to-roll instance that is inited but not started;
you could deploy that in a new JVM and switch it on when triggered. I'd need to think about
that design a bit more though
                
> Augment Service model to support starting stopped services
> ----------------------------------------------------------
>
>                 Key: HADOOP-9933
>                 URL: https://issues.apache.org/jira/browse/HADOOP-9933
>             Project: Hadoop Common
>          Issue Type: Improvement
>    Affects Versions: 2.1.0-beta
>            Reporter: Karthik Kambatla
>            Assignee: Karthik Kambatla
>              Labels: service
>
> For ResourceManager-HA (YARN-149 and co), we would want to start/stop/start RM's active
services as it transitions to Active/Standby/Active respectively. In the current service model,
we can't start the services that are already stopped.
> Would be nice to augment this. To avoid accidental restart of stopped services, we can
add another API: start(boolean restartIfStopped). Thoughts?

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