Hi Tom,
Can't say I'm one of the experts.
I've been trying to determine the differences and similarities between
OSGi and Project Jigsaw and the changes to Java 7 to support modular
systems.
This article is interesting: http://www.infoq.com/news/2009/06/jigsaw
It reports that OSGi has a dependency concept similar to Jigsaw called
fragments, however that fragments don't themselves express dependencies,
to form a dependency tree as such. If you've ever played around with
Debian's dpkg package manager, you'll know what I'm talking about.
I'd personally like to see what direction Oracle takes with the merger,
perhaps there may be a convergence, cross pollination, competition or
something similar, before we commit to OSGi or Jigsaw, perhaps
dependency trees might assist with solving the fragmented container
conundrum, I don't think we'll need to wait too long, we can get AR2
rolled in the mean time.
One component that does have my interest is the possibility of class
file versioning, (not Java bytecode versioning) so two incompatible
versions of a class can coexist in the same classpath or runtime. I was
thinking that this would be useful for migration of live River djinn's,
where incompatible class files could exist with dependency or class file
versioning while one was phased out or trialled.
I'm also thinking that if we add support of compression to the http
codebase (and serialization), we can download individual class files
over the network individually instead of entire jar files (repeatedly
compressed class files would be cached, to reduce CPU overhead). This
might make performance a bit snappier when only requiring a few classes
from a large library that would normally be stored in a jar for instance.
I'd like to do something about packaging a Kerberos KDC Server (thinking
TripleSec) with River, with support for RBAC, so that it runs out of the
box to speak.
Translation of remote interfaces with OSGi sound interesting, River
might become a migration path for those that needing something more
powerful.
Cheers,
Peter.
Tom Hobbs wrote:
"I know you guys are very busy, but it would be nice if the most
experienced Jini/River software engineers were able to dissect the
[OSGi] RFC 119 and provide an assessment as to how or if it is "suited"
for Jini/River. I know it's tough to allocate time to do that though."
Well, in the absence of the most experienced you're left with me. :-)
For added confusion, I don't know a whole heap about OSGi either, so the
follow is a likely mix of over simplification and misunderstanding.
If that sounds useful, continue reading...
This is the complete document, I skipped down to RFC 119 only;
http://www.osgi.org/download/osgi-4.2-early-draft.pdf
The RFC discusses the concept of a "Service Registry" which looks an
awful lot like a River ServiceRegistrar. Delving further into the RFC
it seems to me that we if we can translate from the specified interfaces
that describe an "OSGi Service" to that which describes a "River
Service" then River could slot in quite nicely as a response to this
RFC.
Much of the work feels like translating from what OSGi say service
descriptions and lookups *should* look like and what River says service
descriptions and lookups *do* look like.
The only tricky part, I think, would be how an OSGi component (which
likely extends something else) can be made into a River service such
that it is discoverable in the usual way. This would be an interesting
problem and raises the circumstance where an OSGi service might publish
itself as an OSGi service, but because it's River underneath, would be
discoverable by pure River clients on the same network also.
Looking at how the RFC specifies what a service description is and what
it looks like, I think that there is mileage in River adopting something
similar. It would be nice, in my opinion, to move away from the
quasi-java config files River uses in favour of something else.
XML makes sense because that's what most of the rest of the world uses -
although I personally don't care for it much.
Someone on the Jini-Users (or similar, I can't quite remember) a while
ago was talking about using Groovy classes to describe service
configuration. Something like this sounds pretty neat, but anything
that needs to be recompiled for changes can take affect is likely to be
unworkable for obvious reasons.
Also, building in a mechanism to provide a similar version-sensitive
lookup mechanism would 1) fit with OSGi nicely and 2) be a useful
feature for River all other considerations not-withstanding.
Anyway, that's this layman's interpretation of this OSGi RFC; if only
for a few days or weeks of spare time to spend putting it together.
Tom
www.sucdenfinancial.com
Sucden Financial Limited, Plantation Place South, 60 Great Tower Street, London
EC3R 5AZ
Telephone +44 203 207 5000
Registered in England no. 1095841
VAT registration no. GB 446 9061 33
Authorised and Regulated by the Financial Services Authority (FSA) and entered
in the FSA register under no. 114239
This email, including any files transmitted with it, is confidential and may be
privileged. It may be read, copied and used only by the intended recipient. If
you are not the intended recipient of this message, please notify
[email protected] immediately and delete it from your computer system.
We believe, but do not warrant, that this email and its attachments are
virus-free, but you should check.
Sucden Financial Limited may monitor traffic data of both business and personal
emails. By replying to this email, you consent to Sucden Financial 's
monitoring the content of any emails you send to or receive from Sucden
Financial . Sucden Financial is not liable for any opinions expressed by the
sender where this is a non-business email.
The contents of this e-mail do not constitute advice and should not be regarded
as a recommendation to buy, sell or otherwise deal with any particular
investment.
This message has been scanned for viruses by Mimecast.
