| Re: [osgi-technology-dev] Python <-> Java Integration via OSGi Remote Services |
Hi Jim,
First, thanks for expressing this sentiment. It's been my feeling for some time that other languages/runtimes (like Python) could absolutely benefit from the innovations from osgi.
Just to be clear, whether or not [1] gets contributed to the osgi-technology project, the repo at [1] is available and works right now, and new contributors can and will be easily added.
Architectural Overview for the Repo at [1]
On the java side, the repo at [1] provides an ECF distribution provider for OSGi Remote Services. The Remote Services specification (chapter 100 and RSA 122) standardizes remote service instance metadata (e.g. EndpointDescription and other specified classes and service properties) for services in the OSGi service registry.
The original assumption for remote services is that both processes (service host and service consumer) would have a service registry...since both were assumed to be Java/osgi framework processes.
For the py4j distribution provider at [1] below, obviously the java/osgi process has a service registry, and so can serve as both a service host/impl, or a service consumer...or both...as per the Remote Services and Remote Service Admin specifications.
For the python process, however, there is no service registry. The purpose of the osgiservicebridge python component is to provide a bridge to the Java-based service registry that uses the standard Remote Services metadata to communicate between the Java and Python processes (both directions). Note that this approach (using standardized meta-data for inter-process service interaction) can/could be done with any language or runtime.
You might ask: but what about the osgi service registry, remote services, (and e.g. declarative services) on non-Java processes? That too can be implemented and that's where I've chosen to reuse the excellent work of the ipopo project [A]. ipopo/pelix already has a python-based bundle layer, a service registry, and many of the features of a full osgi framework. Years ago, I contributed to ipopo an impl of RS/RSA (in pelix/rsa module and sub-modules) and also contributed a python-based distribution provider (along with a few other distribution providers) that uses the osgiservicebridge to communicate between the ipopo/python service registry and the java service registry. With ipopo+osgiservicebridge running in python, it's possible to have python-based service impls register themselves in the ipopo service registry, be exported by the python rsa impl, be imported by the java/osgi rsa impl, and consumed by the java process (e.g. injected by declarative services). A tutorial with an example ipopo service registry <- RSA -> java service registry interaction is here [B].
What's the point? As the sole implementer of the repo at [1], I
already make this functionality available via [1]. I can also
contribute this codebase in some form to the osgi technology
group, and am proposing to do so. It could be contributed under
the ECF project (which I lead) or under a new project. I've
spoken with the creator and maintainer of ipopo (Thomas Calmant)
and he would consider contributing ipopo + the ipopo RSA impl, but
that would need to be a separate discussion from the one I'm
initiating here since I don't hold the ipopo copyrights for the
whole ipopo codebase.
There are 3 other features in the Python.Java distribution provider that have not been completely documented yet. If interested in another email describing those features please just respond to this posting positively and I will describe these features with example code references from [1].
Thanks,
Scott
[A] https://ipopo.readthedocs.io/en/1.0.1/
[B]
https://ipopo.readthedocs.io/en/1.0.1/tutorials/rsa_pythonjava.html#
Dear Colleagues,
I find this project interesting to have integrated into OSGi. We are generally interested in extending the OSGi model to code running outside a JVM and this goes in that direction. If we can add contributors, even better.
Sincerely,
James
On 7/8/24 17:10, Scott Lewis via osgi-technology-dev wrote:
On 7/8/2024 5:06 AM, Mark Hoffmann via osgi-technology-dev wrote:
Hi Scott,
thank you for this request. In general we are interested having such a provider that allows communication between Python and Java via Remote Services.
We already doing that as well in a custom component to trigger ML applications, that are implemented in Python.
So, having a distribution provider would be nice.
I have seen the Py4J project made its last release in 2022. Is there still something happening in that project?
I'm aware that the primary maintainer for many years (Barthelemy Dagenais) stepped away from that role a couple of years ago, but that others (Apache Spark committers, Eclipse Foundation committers such as Jonah Graham, who is a committer on several Eclipse projects) have taken up that maintenance mantle. In my usage for implementing a distribution provider, I've not found any major problems so far.
Just to get it right, the contribution would consist of Python and Java components?
Yes. The repo I've provided has several osgi bundles, and the primary python component (in that repo) is the osgiservicebridge, which is available via pip.
Just to be clear, some years ago I also contributed a full python-side RS/RSA implementation to the iPopo project. https://ipopo.readthedocs.io/en/1.0.1/ in rsa package. This python impl of the pelix/ipopo/RSA implementation depends upon osgiservicebridge.
It would be great, if we could discuss that topic, maybe in one of the next specification calls. I would clarify that. Anyway, you are always invited to participate these calls.
Please let me know when this is to be discussed and I'll see if I can attend. I would prefer written questions and answers, however...either here or some other appropriate forum.
Scott
_______________________________________________
Regards,
Mark
Am 04.07.24 um 05:45 schrieb Scott Lewis via osgi-technology-dev:
Howdy,
For many years, the ECF project has had an implementation of the OSGi Remote Services (100) and Remote Service Admin (122) specifications. I believe ECF's RS/RSA impl is currently still used in the OSGi compatibility test suite.
One of our distribution providers enables remote services between Java and Python[1]. It uses the Py4j protocol to do this. Py4j is an open source project [2] that is used for Apache Spark on the server-side (I believe), Eclipse EASE project, and other projects and products/services.
As per the OSGi Remote Services specification, a service registry exists in both the Java and Python processes, and the distribution provider connects them (via osgi-standardized meta-data aka the endpoint description) to export and import services between the two processes. [1] has all the Java and Python components to implement this distribution provider, along with some utilities and examples. This distribution provider can also use Google protocol buffers as the serialization mechanism and so it happens to work well with the both gRPC (based upon protocol buffers) and bndtools-based grpc tooling [3].
If there is interest and community support I would be willing to contribute this distribution provider to the Eclipse community, perhaps as an effort to integrate java and python-based services and apps at the service level for a broader 'artificial intelligence' effort at Eclipse.
Scott
[1] https://github.com/ECF/Py4j-RemoteServicesProvider/
[2] https://www.py4j.org/
[3] https://github.com/ECF/grpc-RemoteServicesProvider
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