[zeromq-dev] Notes from a hackathon

AJ Lewis AJ.Lewis at quantum.com
Thu Feb 5 20:41:24 CET 2015

On Thu, Feb 05, 2015 at 09:55:10AM -0800, Joe McIlvain wrote:
> FWIW, we are currently using a patched version of zproto message codec
> to support multi-hop messages by tracking routing info as an envelope
> of zero or more frames instead of as zero or one frames.  I'm not
> afraid of change, but I'm still trying to work out how we are going to
> change our architecture to not use multi-hop request/reply multi-frame
> semantics.

Is the plan really to drop multi-hop routing?  That seems like a bad
idea if that's what's going on...we're using multi-hop routing quite
extensively.  What's the replacement?  I haven't been able to figure
that out from this thread.

Can't the non-multipart message routing headers handle multiple hops?


> One thing I thought I'd bring up here is zmq_proxy, which we are using
> extensively to funnel traffic from many client (DEALER) sockets on a
> single machine so that we can redirect them all to a different server
> (ROUTER) at will.  This is part of why we support a variable number of
> hops between client and server.  It's not clear to me whether
> zmq_proxy could work correctly or at all with CLIENT/SERVER, or what
> our course of action would be if we could not have any zmq_proxy
> layers between client and server.  Our redirector would probably have
> to become an actor that has sockets that connect are connected to each
> client and are able to instruct them to disconnect from the current
> server and connect to another (specific) one.  We'd also have to
> figure out a way to synchronize this so that all clients are fully
> disconnected from the first server before any start connecting to the
> second.  Also, it would sound like this layer would have to speak a
> different zproto protocol than the main one we have implemented for
> the main flow of client/server messages, adding another zproto model
> to maintain.
> Again, I'm not afraid of change, but I just wanted to bring up a case
> where multi-hop request/reply was (IMO) an elegant and simple solution
> and the alternative would actually be adding complexity.
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AJ Lewis
Software Engineer
Quantum Corporation

Work:    651 688-4346
email:   aj.lewis at quantum.com

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