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From "Hawkins, Joel" <Joel.Hawk...@compuware.com>
Subject RE: OSGi Binding
Date Mon, 13 Nov 2006 13:48:33 GMT
Tuesday 8 PST works for me as well.

Cheers,
Joel

-----Original Message-----
From: Wengatz, Nicole [mailto:nicole.wengatz@siemens.com] 
Sent: Saturday, November 11, 2006 2:01 PM
To: tuscany-dev@ws.apache.org
Subject: RE: OSGi Binding

Tuesday 8 PST works for me.

Thanks
Nicole 

-----Original Message-----
From: Jim Marino [mailto:jmarino@myromatours.com] 
Sent: Friday, November 10, 2006 8:05 PM
To: tuscany-dev@ws.apache.org
Subject: Re: OSGi Binding

Monday early morning is bad for me (I have a meeting starting early).  
Could we do Tuesday 8PST? I have a similar problem with corporate
firewalls. One way I found around this is to tunnel IRC traffic through
an SSH connection to an external shell account (Joel, you may be able to
use your Apache shell account). I use OS X TunnelManager to automate
this and I believe Putty on Windows will work. Of course, I'm not
telling anyone to break corporate security policy... :-)

If this time doesn't work for people let me know some alternatives that
would work.

I'll respond to the questions below separately.

Jim



On Nov 10, 2006, at 7:53 AM, Hawkins, Joel wrote:

> Hi guys,
>
> I'm EST (just barely). Like Nicole, I'm stuck behind a corporate 
> firewall.
> Today's looking problematic for me. I'm game for either Monday (I'll 
> just work from home) or possibly sometime this weekend.
>
> Some questions in the meantime:
>
> A runtime can have multiple root system composites, each isolated from

> another, and each system composite may have multiple root application 
> composites. Do I (finally) have it right?
>
> Is it sufficient for the root system composites to be isolated with 
> respect to wiring (in other words, based on visibility of components 
> available within the root system composite), or must they be isolated 
> based on class loaders as well. I'd like to make sure that the 
> fragment bundle solution is insufficient before we go off and 
> re-invent fragment bundles. ;-)
>
> Thanks,
> Joel
>
> -----Original Message-----
> From: Wengatz, Nicole [mailto:nicole.wengatz@siemens.com]
> Sent: Friday, November 10, 2006 2:48 AM
> To: tuscany-dev@ws.apache.org
> Subject: RE: OSGi Binding
>
>> Sure. I could be available. Nicole, what Timezone are you in? I'm 
>> PST,
> Joel, I believe you are CST.
> I'm CET (Germany). Having the IRC in the evening (e.g. 19:00 CET or
> later) would be fine for me.
> I assume it's anyway easier for me to attend from home (due to the 
> companies firewall).
>
> Best regards
> Nicole
> -----Original Message-----
> From: Jim Marino [mailto:jmarino@myromatours.com]
> Sent: Thursday, November 09, 2006 11:14 PM
> To: tuscany-dev@ws.apache.org
> Subject: Re: OSGi Binding
>
>
> On Nov 9, 2006, at 6:44 AM, Hawkins, Joel wrote:
>
>> I think an IRC might be helpful.  Comments below:
> Sure. I could be available. Nicole, what Timezone are you in? I'm PST,

> Joel, I believe you are CST.
>
>>
>> -----Original Message-----
>> From: Jim Marino [mailto:jmarino@myromatours.com]
>> Sent: Thursday, November 09, 2006 1:12 AM
>> To: tuscany-dev@ws.apache.org
>> Subject: Re: OSGi Binding
>>
>>> ...services. I would also like to avoid proxying the OSGi services 
>>> if possible.
>> Can you define what you mean by proxying the OSGi service? Sorry if 
>> I'm being dense. Are you referring to support for an optimized wire?
>>
> Yes basically an optimized wire so we don't need to proxy.
>
>>> 2. The OSGi container would isolate SCA application composites 
>>> according to its classloader semantics.
>>
>>
>>> Currently, Tuscany has two composite trees, an application and 
>>> system
>>> tree:
>>
>>
>> 	Runtime
>> 		|
>> 	       /\
>> 	     /    \
>> 	   /     Root System Composite
>>            /	
>> Root Application Composite
>>
>> Why only one root application composite? The code I have today hosts 
>> one root system composite and multiple root application composites 
>> (applications pretty much correspond to bundles).
> Sorry, I'm ASCII-art challenged. The above tree could be extended to 
> include multiple leaves. The root application composite can contain 
> 0..n composite children, which would correspond to application 
> deployed in the runtime. I just tried t simplify it here to highlight 
> that there are two sides of the runtime tree.
>> The reason I did this
>> was so that I could "name" the individual applications (for external 
>> management, etc). My reading of the Host API was that there was a 
>> Highlander model (there can only be one) when it comes to 
>> applications, which makes sense in the context of a web-app 
>> deployment, but not as much under OSGi.
> Yes agreed. We don't have the Highlander model here. App composites 
> would be deployed as children of the root app composite (or children 
> of those children).
>
>> What made me think that was that the root application composite had a

>> name.
>>
>>> The root composites may contain child composites. The system 
>>> composite tree contains runtime extensions such as Axis. Each 
>>> composite has its own classloader. This maintains isolation between 
>>> application composites and runtime extensions.We plan on introducing

>>> a multi-parent classloader for system composites. This is arises 
>>> from the need to support scenarios where application code may need 
>>> to access dependencies associated with a system extension. For 
>>> example, application code may need to access classes in Spring. 
>>> These classes need to be shared with the application composite 
>>> classloader. We were planning on loading dependencies that needed to

>>> be shared in a parent classloader of the system extension 
>>> classloader. The former classloader would then also become a parent 
>>> of the application classloader (which would have multiple parents).
>>
>> Comments below at the end of the extension discussion.
>>
>>> One issue is going to be reconciling this scheme with OSGi's 
>>> classloading infrastructure. In relation to this, I was thinking we 
>>> would want a common packaging mechanism for Tuscany extensions 
>>> across host environments. For example, the Axis2 extension should 
>>> not have to be repackaged or modified when deployed on Tomcat or 
>>> Equinox.
>>> Application composites, however, could be bundles. I was thinking 
>>> there would be one Tuscany runtime deployed to an OSGi container.
>>> This would get bootstrapped (as Joel mentioned) by a BundleActivator

>>> and would look similar to the web app launcher with one exception.
>>> Namely, while the web app launcher boots the runtime in a separate 
>>> classloader, the BundleActivator would not need to do this and would

>>> instead boot Tuscany in the bundle classloader. The Tuscany runtime 
>>> bundle would consequently  have to export classes used by 
>>> applications such as SCA API.
>>
>>
>>> Applications would be deployed as bundles as well. It would be nice 
>>> if we could listen to bundles coming online and check for SCA scdl 
>>> (configuration files). If one is found, we load the bundle as an 
>>> application composite and stick it in the runtime application tree.
>>> The classloader for this composite would be the bundle's. The bundle

>>> itself would have to import certain SCA packages (i.e. the ones 
>>> exported by the runtime bundle).
>> I think I've got this.
>>
>>> The hard part is going to be figuring out how to deal with 
>>> extensions. Specifically, in the case I mentioned above where 
>>> application code needs to reference certain extension classes. I 
>>> would like to avoid having special packaging for Tuscany extensions 
>>> when deployed to an OSGi container versus the Servlet container. So,

>>> we could deploy the same Axis2 extension to Tuscany on an OSGi 
>>> container and Tuscany on a Servlet container. This would mean the 
>>> runtime would have to behave slightly differently depending on this 
>>> host. In this respect, perhaps what we could do is instead of 
>>> creating a parent classloader to the extension and also having it as

>>> a parent to the application, we could have OSGi manage this? One way

>>> to do this would be for a particular extension to use just the 
>>> bundle classloader and programmatically export packages that need to

>>> be shared (is there an OSGi api to do this, I recall a "dynamic 
>>> export/ import")? One the application side, the bundle import those 
>>> packages.
>>
>> OSGi has a concept known as a Bundle Fragment. A fragment is packaged

>> as a separate bundle, but at runtime acts is if it were packaged 
>> directly as part of the host bundle. My thought was to package 
>> runtime extensions as fragments, and designate the sca kernel bundle 
>> as the bundle host.
>> Add to that a mechanism to populate the system composite tree with 
>> the extensions, and you've got something that (to me) sounds very 
>> much like what you've described above. Application bundles could 
>> specify a dependency on the sca kernel bundle, at inherit classloader

>> access to all the extensions as a result.
> For system extensions, I would like to have a uniform packaging scheme

> that works across different host environments. Specifically, we would 
> have a jar that is contributed to the runtime. That jar would be the 
> same (e.g. Axis2 extension) and could be deployed in  a war, to the 
> standalone or to the OSGi container. The mechanism for how that jar is

> contributed to the runtime may vary. So, for example, in a war, it may

> go in the /lib directory. For OSGi bindle fragments, is there a 
> deployment API/mechanism where I can take a plain jar (i.e. no OSGi 
> manifest entries), hand it to the OSGI container and declare that it 
> is a fragment (maybe it is something specific to Equinox)?
>>
>> What this doesn't do is allow you to hide extensions from particular 
>> applications. Is this a requirement? From your diagram above (where 
>> there's a single system composite tree) I'm assuming its not, but of 
>> course I could be wrong :-).
>>
> Yes we need extensions to be hidden from the application. However, we 
> may need some classes from the extension to be visible. For example, 
> an extension may hide its StAX parser implementation but wish to 
> expose an API for applications to use that is also used by some 
> internal code (Spring does this with ApplicationContext). In 
> standalone we would load these classes in a classloader that was the 
> parent to the extension classloader. This parent would then also 
> become a parent to the application composite classloader, which would 
> have multiple parents. In OSGi I  was thinking we would take a 
> slightly different approach. Instead of creating a parent classloader 
> that was shared, we would programmatically export those shared classes

> in the extension bundle. The application bundle would then import 
> them.
>>> Do you guys think this makes sense? I have some skeletal code 
>>> checked into the OSGi and Equinox projects.
>>
>>> Also, I would like to try and get any code checked into the trunk 
>>> since this will make things easier. Joel, when you get things synced

>>> back up submit a patch and I can apply it. Similarly, Nicole, if you

>>> have code that could benefit from being checked in, let me know.
>>
>> I'll get back to the patch. There's some code in there I need to 
>> remove
>> - it was placed in as part of a demo I did at EclipseWorld that 
>> showed a sample WSDM integration using a management annotation. Sorry

>> for the delay on that - swarms of distractions here.
>>
> NP I'm the same way. If possible it would be great to see/hear about 
> what you did.
>>
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>
>
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