[erlang-questions] integrating inter-process protocol checkers

[Rich Neswold]

On Sat, May 17, 2014 at 10:33 AM, Vlad Dumitrescu <vladdu55@REDACTED> wrote:
> I was thinking today (obvious from the number of mails to the list :-) ) and
> was considering how great idea protocol checkers are and wondered why they
> aren't used and popularized more.

Protocol checkers are wonderful.

> One of the possible reasons is that in order to be able to use them
> everywhere, one has to use a specific architecture: with middleman processes
> in front of every server process. This is somewhat clunky, introducing
> elements that are not related to the application domain. Besides, it makes
> it difficult to add them to existing applications.

A colleague and I have developed a protocol compiler which takes a
protocol specification file and generates source code to
marshal/unmarshal the messages. It's very similar to Google's protobuf
idea and we seriously considered using their's, but there were some
requirements at Fermilab which it didn't meet, so we rolled our own.
We support C++, Java, Objective-C and Erlang (which are all used in
our Control System) and we also target Python and OCaml (which are
experimental.)

We don't use middleware: each generator uses the target language's
method of choice to prep an outgoing message. So, for example, the C++
code will write to a stream; the Erlang code builds a binary (which
can then be sent to a socket.); etc.

The generated code for each target language validates the messages and
will only succeed if every required field is present and is of the
correct type and in range. Handling protocols, before this tool was
created, was tedious and error-prone. Now adding features is a breeze
and we regularly add or refactor protocol messages.

-- 
Rich