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


But even DS only knows about started bundles. If a bundle is started after DS has processed some bundle, then new services can be registered. There is no way for DS to know about all possible services being ready since some may come from bundles yet to be started. The best DS could tell you is that it is done processing services from bundles that are currently started.

It is far better in the long run for the application to handle dynamism. Anything you do today to try and enforce some ordering will likely fail in the future when some thing changes about the set of installed bundles.

--

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

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





From: "Cortez, Otto" <OttoCortez@xxxxxxxxxxxxx>
To: "Equinox development mailing list" <equinox-dev@xxxxxxxxxxx>
Date: 2008/09/03 02:48 PM
Subject: RE: [equinox-dev] When is DS done loading services?





It is more important for us to know what functionality is installed and available before parts of the application execute then it is for us to support dynamism.  I would like to keep the dynamism if we can, but to do that and provide reliable execution I think the application would need to guarantee that all services known through the bundle manifests will be initialized before we start processing.  I guess using extensions might be a better fit.
 
Iâm not sure if we need DS to synchronously register services as much as some way to listen to DS events or know its state, like is it just sitting around waiting for more bundles to be activated or deactivated.  I was focused on services being managed by DS since I thought DS would know weather it was done initializing all services listed in the active bundlesâ manifest files and then we would be able to say to users which may supply functionality, well if you use DS then we could guarantee that we wouldnât start until DS had initialized your services.
 
Thanks,
Otto
 



From: equinox-dev-bounces@xxxxxxxxxxx [mailto:equinox-dev-bounces@xxxxxxxxxxx] On Behalf Of BJ Hargrave
Sent:
Wednesday, September 03, 2008 7:22 AM
To:
Equinox development mailing list
Subject:
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
hargrave@xxxxxxxxxx

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
processed.

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.

Stoyan


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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