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From Pierre De Rop <pierre.de...@gmail.com>
Subject Re: [DS} major refactoring of dependency management
Date Tue, 18 Dec 2012 14:38:33 GMT
Hi David,

Just to let you know I did some quick testing and I did not find any
I think you can commit if you think you are ready.


On Sun, Dec 16, 2012 at 6:03 AM, David Jencks <david_jencks@yahoo.com>wrote:

> I've been working on fixing the numerous timing holes in ds dependency
> tracking and I think I'm getting close to being willing to commit the
> results.
> I've put what I have now up at github at
> https://github.com/djencks/felix.git in the service-tracker-3 branch.  If
> anyone is interested in taking a look that would be great.
> There are two main parts to my refactoring:
> 1. use a copy of ServiceTracker modified for the requirements of DS.
> Service tracker actually tracks services properly and doesn't emit
> duplicate events, miss events, etc etc.  I don't think its possible to
> track services properly in any simpler way.  Modifications are primarily:
> -a- we need a new Added event after the service is put in the tracking map
> since we may want to use the event as a trigger to try to activate the
> component, querying the service tracker for matching services.  So the
> service better be in the map :-)
> -b- Closing needs to happen in 2 steps in order to deal with filter
> changes.  The initial close step needs to unregister the service listener
> and return the current state of the map.  The second close step can clear
> the map.
> -c- We need to expose the internal tracker for some locking.
> -d- expose the tracking count.  This already was in the base tracker code
> but not used in ServiceTracker.  we need it.  This is an event counter, not
> the number of tracked services.
> 2. For each component instance, keep track of the initial tracking count
> when we query for existing services and the final tracking count when we
> unbind services.  Then we can ignore, for a given instance, events that are
> "before" (have a lower tracking count than) the open and "after" (have a
> higher tracking count than) the close thus avoiding duplicate and missing
> bind and unbinds.
> I also put the different multiplicity/dynamic styles of reference in
> separate customizer classes which I think simplifies the logic.
> There are a few other bug fixes in there too:
> FELIX-3729
> [DS] Track dependencies by imitating ServiceTracker and keeping a list of
> actual service references all the time      (this is most of the work)
> FELIX-3738
> [DS] ComponentInstance.getServices(String refName) is implemented wrong
> for 0..1 and 1..1 refs
> FELIX-3825
> [DS] make logging more useful by including component ID when known
> As a side effect, a lot more of the circular reference situations are
> getting resolved.  I'm not entirely sure why, but I'm not objecting.
> There are a lot (?) of unused parts of service tracker.  So far I've made
> minimal modifications to the copied osgi code in the interests of
> maintainability in case the osgi code changes, but I could easily be talked
> into removing the stuff we don't use.
> thanks
> david jencks

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