Capnproto RPC for Java - work in progress.

[Vaci]

Hi all,

With some free time in my hands, I decided to have a go at writing the RPC protocol in Java, as least for two-party connections, using Java 8 CompletableFutures as a analogue of the KJ async event management layer. 

I have got as far as being able to transfer capabilities between clients, and make calls to remote methods. There is still a fair amount to do in handling pipelining, disconnection and finish operations, but the implementation looks promising so far. The code sticks fairly closely to the C++ original, mostly to make my debugging efforts easier.

I hope to start looking at extending the Java compiler stage for interfaces next, now that I have an idea of what the generated client and server code might look like.

If anybody is interested,, the code is on Github:

   https://github.com/vaci/capnproto-java-rpc

Cheers,

Vaci

[David Renshaw]

Cool! Thanks for sharing.

How are you approaching concurrency? Are objects constrained to execute on a single thread, as in the C++ implementation?

- David

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[Vaci]

Yes, my assumption so far is that each RpcSystem will execute on a single thread. There's no asynchronous dispatch of completion handlers in the code, so I expect only the socket IO (which completes on the background thread pool) will need synchronisation.

Vaci

[Vaci]

Made some  progress over the last week or so - can now generate client and server interfaces,  and make pipelined calls between two RPC systems. Next is to test disconnection and exception handling.

I have not attempted to generate code for generic interfaces - it looks like there is some support already in the compiler, but it wasn't entirely clear to me how to use the generated output?

Vaci