Re: Distributed Systems Annex, data sharing between programs

[Marius Amado-Alves <amado.alves@gmail.com>]

> Our middleware supports synchronous calls, but they are implemented on top
> of an asynchronous layer as send/request + wait. (Kasakov)

(Secret technology?)

This thread is fascinating.

Make RPC based on messages (Kasakov and others) or vice versa (Obry and others)?

FWIW, I tend towards the latter. It's clearly the Ada way:

Ada offers asyncronous control already. Chapter 9. So it's just a matter of wrapping the RPC with the desired asyncronous logic (a task, the time out idiom, ATC...)

Distribution and synchronicity are orthogonal dimensions. Probably Ada has been designed with this in mind. Distribution => Annex E. Synchronicity => chapter 9.

Yes, an implementation of Annex E may be based on messages e.g. sockets, and therefore asynchrounous RPCs in Ada (let the oximoron pass this time) will compile to an asynchronous-synchronous-asynchronous tower. Maybe there is a performance penalty here. Maybe for some projects climbing this tower would take too long, and so they use a message protocol directly for the message abstration. I cannot think of any other reason to depart from the Ada way.

(Is it really true that Polyorb is the only Annex E implementation that exists? Or just the only libre one?)