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Re: [ecf-dev] RPC for Remote P2 repositories

Hey Thomas

The p2 repo API has not been particularly designed to support remoting. That is, I*Repository was not really intended to be used as a remote interface. Frankly we just did not think of it that way. Instead we imagined that people wanting to have a repo on another server would implement the actual repo using whatever server side technology appropriate (e.g., database, sql, ...) and then implement a "client-side" I*Repository. The client side would talk to the server using mechanisms appropriate to the configuration. There is no expectation that the server be Java etc etc. The client is also free to do any amount of caching etc that it wants to.

In this way the users of I*Repository are completely isolated from the implementation details of the server and the repo implementors are free to optimize/implement as they choose.

Does your usecase fit this model?

Of course, it would also be interesting to consider changes to the p2 API to better facilitate remote calls. Please open enhancement requests if you see any such opportunities.


Thomas Hallgren wrote:
I'm implementing a remote service for p2 repositories. Initially, I chose JSON as the RPC mechanism since its simplistic, very lightweight, and fairly mature. We've also had some good experiences with it when we did the AOL XDrive implementation in the Spaces project.

In this case I have an Equinox based OSGi framework on both sides and perhaps it would be far more efficient to use ECF remote services? I have the following requirements:

1. I must be able to pass some objects by value that are neither nor standard java beans. The only way to serialize/deserialize them is to register custom serializers. Typical examples are the p2 ArtifactDescriptor or ArtifactKey.

2. It must be possible to register custom serializers based on interfaces (i.e. IArtifactDescriptor).

3. I need to pass some objects by reference. Either the RPC mechanism must manage garbage collection internally or I must have access to some API that allows me to do an efficient implementation. My current JSON based implementation uses java.lang.reflect.Proxy instances in the client, registered in a WeakHashMap. I then keep track of object-id's that are no longer used and periodically tell the server to drop them.

4. It must be possible to register callable references based on interfaces.

5. I must be able to limit the access to some methods/interfaces based on session data (isUserInRole() or something similar).

How will ECF remote services stand up to these requirements?

Thomas Hallgren

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