How to use R-Osgi to get remote “exported-package”?

Question

R-Osgi provides us a way to call service from a remote OGSi container. WebSite: http://r-osgi.sourceforge.net.

I'm new to R-OSGi and now I want to split my OSGi container into small ones and interact each other by R-Osgi because it's too huge. But it seems R-OSGi only provides a way for Registered Service. We know that the most popular way to interaction between 2 bundles besides Service, "exported-package" is also widely used.

So, is there anyone familiar with R-OSGi and know how to use "exported-package" from remote OSGi container?

Thanks for any response.

Answer 1

If you think about it, attempting to handle the remote importing/exporting of packages is very complex, fragile and prone to error; you'd need to send all bundle lifecycle events over the wire, and honour them in the importing system (which would require caching).

Additionally the framework would need to know ahead of time to use these class definitions (you cannot instantiate a class that references classes that aren't available to your classloader). A remote bundle's classloader may depend on classes from another classloader, this chain could go round and round a network making classloading take ages.

Put another way; your local bundles will never resolve without the class definitions they depend on, and considering there could be thousands+ of potential remote exporters on a network/hardware with very poor SLA, this wouldn't scale well or be very robust considering the fallacies of distributed computing.

If we tried to do remote packages, the framework would need to import all exported packages from all available remote nodes and then select just one to import each bundle export from (this would be arbitrary and if the select node goes down, the whole import remote package process would have to triggered again).

What you need to do is separate you api/interfaces from your implementation, you then distribute the api bundle to all nodes that need it and then use dOSGi to import services.

Apologies if this unclear or waffly but it should explain why it's simply not practical to have remote exported packages.

On a side note; I'm not sure if r-osgi is being actively maintained or is up-to-date with the latest Remote Services Admin spec, from looking at the last commit to SVN trunk was 14/02/2011. There's some alternative dOSGi implementations listed here (but avoid CXF).

EDIT: In terms of deployment, distributing your bundles (and configuration) can be done from an OBR (there are number of public ones and several implementations Felix/Eclipse), or a maven repository can be reappropriated with pax url handler.