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From Graham Charters <gchart...@gmail.com>
Subject Re: Do we really need Quiesce support?
Date Thu, 12 Feb 2015 10:25:51 GMT
Hi David/Christian,

Here is what Mark wrote, that didn't make it:

"Quiesce is about stopping a bundle gracefully prior to its uninstallation,
which is why we've had no need to implement a 'restart' capability. We
currently use Apache Aries quiesce within IBM WebSphere Application Server.
It's used in a scenario where an administrator is replacing some of the
bundles within a running application. The code has been in use in that
product for some years now so yes, I'm sorry but we do have a definite need
for the facility."

Essentially, we use it to notify containers/extenders of bundles that are
about to be uninstalled (prior to that actually being done) so they can
perform house-keeping ahead of uninstallation being kicked off.

Regards, Graham.


On 12 February 2015 at 10:12, David Bosschaert <david.bosschaert@gmail.com>
wrote:

> I'd like to understand what the use-case for the Quiesce functionality
> actually is. Graham, would you like to explain the actual benefit that
> it provides?
> Once we understand that better, maybe we can think of a structure that
> maintains Quiesce support with less complication in the code...
>
> Cheers,
>
> David
>
> On 12 February 2015 at 10:30, Graham Charters <gcharters@gmail.com> wrote:
> > Hi Christian,
> >
> > Apologies for not responding sooner, Mark Nuttall tried to reply on this
> > thread, but his email did not make it.  We use Quiesce support in
> WebSphere
> > so need this to be left in.  Please do not remove it.  Many thanks.
> >
> > Graham.
> >
> > On 12 February 2015 at 08:02, Christian Schneider <
> chris@die-schneider.net>
> > wrote:
> >
> >> I created an issue to track the removal of the quiesce support in aries
> >> jpa.
> >> https://issues.apache.org/jira/browse/ARIES-1297
> >>
> >> I have prepared a commit and plan to apply the removal on next monday if
> >> no one opposes.
> >>
> >> Christian
> >>
> >>
> >> On 10.02.2015 09:15, Christian Schneider wrote:
> >>
> >>> In several places in aries we support the Quiesce API. As far as I
> >>> understood its purpose is to shut down bundles without actually
> stopping
> >>> them. It does not seem to be any standard as the interfaces are in the
> >>> Aries namespace.
> >>>
> >>> The problem with it is that it complicates the code a lot. For example
> in
> >>> jpa container we create a proxy for each EntityManager that also
> supports
> >>> quiesce methods even though they are
> >>> not part of the EntityManager interface. The code in other modules is
> >>> similarly affected.
> >>>
> >>> Besides this I do not see anyone using the API. I am also not sure why
> we
> >>> need it at all as OSGi already has nice lifecycle methods to stop
> bundles
> >>> which should have a similar effect if implemented nicely. One other
> >>> disadvantge of Quiesce is that you can only shut down a bundle. You
> can not
> >>> restart it again.
> >>>
> >>> So the question is: Do we really need to support the Quiesce API? The
> >>> code would be a lot less complex and error prone without it.
> >>>
> >>> WDYT?
> >>>
> >>> Christian
> >>>
> >>>
> >>>
> >>
> >> --
> >> Christian Schneider
> >> http://www.liquid-reality.de
> >>
> >> Open Source Architect
> >> http://www.talend.com
> >>
> >>
>

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