Peter, Okay. I see. You are not using "pattern" in the sense of pattern brought into computer science by the Gang of Four. You are using that term more in a plain English sense. I think this is misleading in this venue and would suggest that you use another word to avoid the possible misunderstanding that you meant "design pattern" as it is used in computer science.
On a more substantial note, I don't think the "pattern" you discuss is the same at all for Jini and OSGi. The services for OSGi are not like the services for SOA. SOA services may or may not be akin to the services for Jini. I am very careful about abstracting or generalizing because, although my first and last love in computer science is architecture, the devil is in the detail. For my part, I think it would be worthwhile to determine the level of Ossification you want. For example, there would be no harm at all in seeing whether you can modularize the jar files into bundles. Once that is done, then you can begin seeing how the actual processes in OSGi match those in Jini. As yet, you do not even know, as I understand it, what OSGi services you want. That would need to be determined, since you will be customizing them. I hope this is helpful and thank you for stating what you were thinking. Mike On Nov 17, 2009, at 8:33 PM, Peter Firmstone wrote: > 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 >> [email protected] >> >> >> >> >> >> >> >> >> >> >
