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From "Amichai Rothman (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (DOSGI-160) RemoteServiceAdmin shuts itself down during startup
Date Mon, 15 Apr 2013 09:12:16 GMT

    [ https://issues.apache.org/jira/browse/DOSGI-160?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13631601#comment-13631601
] 

Amichai Rothman commented on DOSGI-160:
---------------------------------------

Thanks for the review and analysis :-)

Just a small correction regarding unregistering services in Activator.stop() - as I understand
it, the spec doesn't say you shouldn't unregister services in stop(), just that it's optional:

{quote}
stop(BundleContext) – This method must undo all the actions of the
BundleActivator.start(BundleContext) method. However, it is unnecessary to unregister services
or Framework listeners, because they must be cleaned up by the Framework anyway.
{quote}

So in theory you should undo everything (including service unregistration), but in practice
since the framework must make sure to clean up after bundles (even if they misbehave), and
will unregister services in any case, you can leave that part out. In our case, I added it
so that the code will be clearer - to me it intuitively looked like a bug before I started
digging in the spec...

To sum it up, the code is correct with or without the unregistration, and putting a comment
stating so explicitly also solves the maintainability issue, so all is well :-)
                
> RemoteServiceAdmin shuts itself down during startup
> ---------------------------------------------------
>
>                 Key: DOSGI-160
>                 URL: https://issues.apache.org/jira/browse/DOSGI-160
>             Project: CXF Distributed OSGi
>          Issue Type: Bug
>          Components: DSW
>    Affects Versions: 1.4.0
>         Environment: Oracle JDK 1.7.0_17, Karaf 2.3.1, DOSGi 1.4.0 (installed from Karaf
feature)
>            Reporter: Amichai Rothman
>            Assignee: Christian Schneider
>             Fix For: 1.5
>
>         Attachments: fix_activator_config_and_sync_issues.diff
>
>
> Every once in a while (quite often) the service export fails. Looking through the logs,
I found the message "RemoteServiceAdmin Implementation is shutting down now" - during Karaf
startup! It appears that the RSA is started, services exported properly etc., but then it
suddenly commits suicide a few moments later with no other error or indication of who/what
initiated the shutdown or why.
> Further investigation shows the DSW Activator is getting a ConfigurationAdmin updated
event with null configuration (according to the OSGi specs, the callback is guaranteed to
be called - either with an existing configuration or with null if none is available). The
current implementation of the callback stops the bundle, shutting down the service and printing
the above log message, but when the configuration is null it does not start it back up, resulting
in the observed behaviour.
> There's also a race condition in the class since from my understanding of the specs the
updated callback is called asynchronously from a separate thread, and since it stops and possibly
starts the bundle, this might cause the start/stop methods to be run concurrently and more
than once (the bundle lifecycle start/stop along with the update-triggered start/stop).
> Finally, while debugging and attempting to fix this I came across a third related issue
- when the bundle is indeed started up again in the updated method (e.g. if removing the null
check or if a configuration is available), the start method then re-registers the ManagedService,
which causes the updated method to be called again, which restarts the bundle again, etc.
- in an infinite loop. In practice I saw the server hang with 100% CPU usage indefinitely,
and in a later session with a debugger the loop was confirmed.
> Attached is a fix for the 3 related issues - when applied together everything seems to
work as expected. I'm new to this project, so please correct anything I've missed.

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