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Re: [equinox-dev] When is DS done loading services?

The whole point of services is that the are dynamic. The fact the DS is "processing" them on behalf of some bundle does not mean that another bundle should know or observe that.

Bundles which depend upon a service need to deal with that service's dynamism. You can't assume a bundle's activator or starting a bundle will synchronously register some services. I would not support an option for DS to synchronously register services during bundle start as this means people will improperly use that.

You may also be seeing an impedance mismatch between the lifecycle of extensions and services. Extensions become active when the bundle is resolved while services become active only when the bundle is started. Switching to use extensions will not allow for dynamism (unless you want to write all the code to use the extension registry API to do so.)

You may be able to use startlevels to mitigate the issue (make sure all bundles providing service B are started before bundles using B), but this is also a hack. It would be better if service A dealt with the dynamics of service B such that service A has a dynamic dependency on service B and is able to accept B's being registered and unregistered at any time.

BJ Hargrave
Senior Technical Staff Member, IBM
OSGi Fellow and CTO of the
OSGi Alliance

office: +1 386 848 1781
mobile: +1 386 848 3788

From: Stoyan Boshev <s.boshev@xxxxxxxxxxx>
To: Equinox development mailing list <equinox-dev@xxxxxxxxxxx>
Date: 2008/09/03 07:51 AM
Subject: Re: [equinox-dev] When is DS done loading services?

Hi Otto,
I guess your problem is connected to the asynchronous processing of the
DS services.
As far as I understand the situation is: your application bundles are
started, then your application is started but at this moment not all of
the DS services are inited yet because they are being asynchronously

Unfortunately currently there is no way to find out when DS completes
the DS services processing.
I think if there was an option that DS bundle process the DS services in
the started bundles synchronously, it would solve your problem. So I
will open bug(enhancement) about that and hopefully this will be
implemented soon.
As a possible workaround you could observe the running threads and when
the thread with name "Component Resolve Thread" disappears this would
mean that DS bundle has no more work to do and eventually all of your DS
services are processed. I realize this is not a clean solution (that's
why I call it workaround) but at this moment I cannot find out a more
appropriate working solution without modifications in the DS bundle.


Cortez, Otto wrote:
> I made a post to the Eclipse newcomers group a few weeks ago, but did
> not get a response.  I donât know if this is the appropriate place for
> this question, but hopefully someone can point me in the right direction.
> We are building a headless RCP application and we would like to use DS
> to make functionality available.  The problem we are running into is
> that not all of the services we declared through DS get loaded and are
> visible before our application executes.
> For example, I have a service A which needs 0..n instances of another
> service B. The issue I'm running into is that if the implementations of
> service B are spread across several bundles, then the service A will not
> have seen all instances of service B when it is called since the
> application starts (and sometimes ends) running before DS is done
> looking through all the bundles and registering all the services in the
> active bundles.
> Is there a way to know when declarative services is done looking through
> the active bundles and loading the services found in them?  Am I missing
> something?
> It seems that using the plug-in registry may solve this issue.  Is that
> perhaps a better way to go?
> Thanks,
> Otto
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dipl. eng. Stoyan Boshev . Department manager
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