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From Peter Firmstone <j...@zeus.net.au>
Subject Re: River & OSGi
Date Wed, 18 Nov 2009 04:33:36 GMT
Mike McGrady wrote:
> I am presently the author of a framework called "Karma" (Kolona 
> Automated Resource Management Architecture) that is open source with a 
> management app under another open source framework AUM (Automated 
> Universal Middleware).
>
> UM  (Universal Middleware) is a more current name for OSGi.
>
> We could have called it DUM (Distributed Universal Middleware) instead 
> of AUM but thought better.
>
> Too bad we did not get on better when I asked you what you meant by 
> "Service Pattern".  (I still have no idea what you mean.)
Here's a Clarification of what I meant by "Service Pattern", from 
Richards Book, page 12, this should clear up any remaining confusion:

"the service-oriented publish, find, and bind interaction pattern: service
providers publish their services into a service registry, while service 
clients search the
registry to find available services to use (see Figure 1.3)."

So there you go it's the "Publish, find and bind interaction pattern"

The point I was attempting to make in the beginning was that Jini, OSGi, 
ServiceLoader and Netbeans Modules all use the "Publish, find and bind 
interaction pattern" to solve different problems, I was trying to lay 
out the understanding to avoid an argument and promote a discussion 
about how to implement utilisation of OSGi within River and its 
applications.

I still haven't managed to achieve this discussion, hopefully the best 
way forward will become more apparent during implementation.

Cheers,

Peter.
> Anyway, this does all you want to do and we have a plan to have it set 
> as a standard with IEEE, where I am a member of the standards 
> committee.  If you check there in a few months, you can see what I was 
> hoping to talk to you about before your ego got in the way.
>
> Good luck with your endeavors.
>
> Mike
>
> On Nov 8, 2009, at 5:06 PM, Peter Firmstone wrote:
>
>> Yes that's the beauty of Services, they provide opportunity for 
>> pluggable replacement implementations.  That's the "Service Pattern"  
>> As we have seen it is possible to use the Service Pattern to solve a 
>> number of different problems.  Eg Netbean Plugins, SPI, OSGi, Jini.
>>
>> I'm looking at OSGi to wire up services inside the JVM as you say.  
>> When I say package, I mean a java package residing in the local JVM 
>> it may or may not be part of a Jini service, it may be a purely local 
>> JVM package, eg a library dependency or local domain package.  For 
>> example, I have package X, version 1 loaded in my local JVM, I need 
>> to have package X version 2 loaded as version 1 isn't compatible with 
>> the new Objects (domain data) I'm recieving in serialized form.  I 
>> need to share this information locally with Package Y that currently 
>> has references to objects in Package X version 1.  The Objects in 
>> Package X version 1 that Package Y references need to have their 
>> class files upgraded.  Without OSGi I can do this by persisting 
>> state, stopping the JVM, restarting and loading package X version 2.
>>
>> I'm not looking at distributed OSGi, but I can see a use case for 
>> utilising a Jini Service, when a local OSGi bundle that performs some 
>> task that could be done optimally if the processing can be moved to 
>> where the data resides, this is just an example there are probably 10 
>> other ways of doing this:
>>
>> A local application bundle that provides an OSGi service locally 
>> queries a remote database using JDBC and performs a considerable 
>> amount of manipulation to that data prior to returning a subset.  The 
>> query and its result are sent over the network using a database JDBC 
>> connection.
>>
>> The processing for that data, if shifted to the machine that has the 
>> database data, would consume significantly less network resources.  
>> EG the data transferred over the network is reduced by a factor of 
>> 100 by processing the data on the database machine after querying.  A 
>> bundle that provides a "local JVM application" an "OSGi service" 
>> could utilise a "Jini Service" to request the data be processed at 
>> the Database machine in a particular manner before receiving the 
>> result.  This function could be locally available as an OSGi service 
>> to some other local application, that application doesn't need to 
>> know about Jini, it is an implementation detail that is abstracted.
>>
>> My objectives are all based around codebase services (objects aren't 
>> locked to their http codebase origin), in combination with OSGi or 
>> something like it, to ensure compatible classes and packages are 
>> loaded among separate JVM instances.  Yes Newton does something 
>> similar, however it is AGPLv3 licensed.
>>
>> I envision a distributed environment where nodes can have the 
>> majority of their packages downloaded and upgraded via codebase 
>> servcies. Providing an evolving cluster, that upgrades it's bundles 
>> incrementally, while maintaining the maximum level of class and 
>> package compatibility.  Think Agile Cluster Running System component 
>> upgrades.
>>
>> People, who are jumping in now because I've mentioned OSGi, are 
>> making assumptions and haven't been following the discussions I've 
>> posted previously about Versioned Classes, Classloader trees, Static 
>> Analysis and Codebase Services, this is frustrating as I was hoping 
>> for some participation.  It seems I can only get attention when I 
>> mention a controversial subject.  What I want is attention to solving 
>> the problems that will make River better.
>>
>> In my note below when I'm referring to the "Service Pattern", I mean 
>> the service pattern that OSGi implements, enables bundles to be 
>> upgraded by loading the replacement bundle in a new classloader,  The 
>> service is a common interface, the new upgraded service is discovered 
>> after it is started.  The alternative is to use delegates to update 
>> references between objects when the Classloader changes as per some 
>> of the other patches I've uploaded.
>>
>> Jini also utilises a "Service Pattern", but to solve a different 
>> problem.
>>
>> I knew this was going to be a difficult topic to present.
>>
>> What we need are separate lists, where people who want to participate 
>> in constructive development to solve problems can do so and another 
>> list where people can pontificate about software ideals and have 
>> disrespectful arguments with each other without holding up 
>> development.  While we're developing we can keep an eye on the 
>> argument list without getting embroiled.
>>
>> Anyway I've said enough, I'm going back to doing the things I need to 
>> do, if someone who has been following my posts to date has 
>> implementation ideas, but are afraid to mention it, please feel free 
>> to contact me directly to discuss, I do need some input to gain 
>> confidence that I'm approaching these problems in the right manner.
>>
>> Peter.
>>
>> Dennis Reedy wrote:
>>>
>>> On Nov 8, 2009, at 1251AM, Peter Firmstone wrote:
>>>>
>>>> I had avoided OSGi purely due to the controversy it generates on 
>>>> this list, however without the Service Pattern one cannot upgrade a 
>>>> package without first persisting everything and shutting down the 
>>>> entire JVM, then restarting.  At least OSGi allows you to stop a 
>>>> bundle and any dependents, persist what you need to then start with 
>>>> a later bundle version if desired, without having to persist or 
>>>> shut down the entire JVM.
>>>
>>> If thats all you want you dont need OSGi. Service lifecycles are 
>>> supported with a variety of container approaches, from JEE, Spring 
>>> to Rio. You also do not need to shutdown the JVM to load new service 
>>> classes.
>>>
>>> Adopting OSGi as a micro-kernel architecture for wiring up services 
>>> inside the JVM is a different thing. Looking at distributed OSGi is 
>>> a totally different thing on top of that. IMO, if you want to 
>>> consider OSGi for River, you focus on the former, not the latter.
>>>
>>>
>>>
>>
>
> Mike McGrady
> Principal Investigator AF081-028 AFRL SBIR
> Senior Engineer
> Topia Technology, Inc.
> 1.253.720.3365
> mmcgrady@topiatechnology.com
>
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