[zeromq-dev] 0MQ + standard RPC

Matthew Long matthew.long at aptomar.com
Tue Nov 29 09:50:43 CET 2011

As a short followup -- I just looked at PyZMQ and it looks like an excellent "pythonic" binding.  In particular, it handles asynchronous calls and queueing calls so that they can be sent via a single socket thread.  

Unfortunately, I am not doing anything in Python at the moment.   



On Nov 29, 2011, at 9:29 AM, Matthew Long wrote:

> Hi Pieter,
> On Nov 28, 2011, at 10:03 PM, Pieter Hintjens wrote:
>> On Mon, Nov 28, 2011 at 8:36 AM, Jakub Witkowski <jpw at jabster.pl> wrote:
>>> On the other hand, making a "RPC-like" system, fully customized to your
>>> application based on ZMQ is very simple; it more or less involves
>>> copy-pasting the dealer/router pattern from the examples and  putting in
>>> your business logic in. Toss in Google Protocol Buffers and suddenly you
>>> have a full featured solution that is both easy to write and very, very
>>> fast.
>> Yes, this is what I'd recommend as well. Google protobufs give you
>> language portability, are fast, and easy to use. There are various RPC
>> examples in the Guide you can start with, see Ch3 and Ch4. I'd suggest
>> either the Majordomo or Freelance patterns.
> Yes, those are a good start.  We already use protobufs for the IDL, service definitions and serialization.
> Where these examples start breaking down when I try to bring them into my existing frameworks:
> 1) Sockets are not thread safe so we need to build scaffolding to protect the socket.  When threads are expensive like in C/C++/etc it makes sense to do this via inproc:// connections, but in other languages (such as Go) where go routines can be multiplexed onto any number of running threads (by the runtime) this is an issue.  
> 2) Clients often want asynchronous messages and callbacks.  That is, the client might send requests 1, 2, 3, 4, 5, but get back 5, 3, 4, 1, 2 -- and we need to pair the request context with the correct response.
> 3) Go is a typesafe language, but we want to be able to do the type conversion when we serialize and deserialize messages.
> All three are already handled in the RPC layer -- the fact that I was reimplementing most of this is what prompted my post to the list.  
> What I am hearing is there are no existing tools to do this and I should implement something myself.  
> It may be that with the appropriate surgery I can fit 0MQ in with existing frameworks -- but this is something that the 0MQ team might want to consider addressing at some point.  While there are language bindings in a ton of languages, a strict port of the C api probably won't be idiomatic in the target language.  If 0MQ fit in easily to the right layer of Go or Java or Python it would be a clear win.  I could use 0MQ with the native RPC system and also implement neat patterns on top of it for PUB/SUB or whatever.  As it stands it is a little bit of a mixed win for us.
> If I do figure out how to cleanly add 0MQ to various RPC systems, I will post what I did to the list.
> Matt
>> -Pieter
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