RPC framework evaluation

Network protocol design is hard to get exactly right, and networking/serialization code has high standards of correctness – all the other code in a project depends on the right data getting sent across the wire. If you're trying to communicate between programs written in multiple languages, that code has to be written (and tested, and maintained) separately in each language.

RPC frameworks offer a nice solution to this problem: write the interface you want your messaging to take in some Interface Definition Language (IDL), and then compile it to working (and hopefully idiomatic) code in a multitude of languages.

However, there are drawbacks:

• We don't control the implementation, which means it is hard to optimize for performance, and harder to add new features later.
• many of the RPC frameworks don't support push notifications from the server to client (implemented by some as "streaming").
• Generally, IDLs require static type definition. This means that we would have to define remote procedure calls as only taking one type. The only really workable approach would be to take a byte array serialized with some other data serializer, and pass that through the RPC. This reduces the usefulness of an RPC framework somewhat, as it can't handle everything. However, having function stubs and having the transport taken care of is still quite useful, especially as the code works in multiple languages.

"Server-Client push" in the table below refers to the ability of the server to push messages back over the same communication channel the client uses to connect to it. BERT, for example, can take an address to deliver a message to when some remote call is done, but it has to be able to connect to that server. Many Geode users use firewalls, which would cause issues connecting to the client. Also, it's more adapted to the actor model than to a client-server model, as we use.