[zeromq-dev] REQ/REP for possibly async comm?

[Andrei Zmievski]

Okay, will give that a try. Is there a reason why I couldn't use PUB/SUB
sockets for this interaction?

-Andrei

On Tue, Mar 27, 2012 at 6:37 PM, Michel Pelletier <
pelletier.michel at gmail.com> wrote:

> If not getting a timely response is an exceptional condition, then you
> can throw away your REQ socket, create a new REQ socket, connect it
> and proceed from there as if it were new.  If it's a common occurrence
> then you can do ROUTER<->ROUTER and track the state of requests
> yourself.  REQ and REP enforce a simple state, if you need a more
> complex state tracking, then you can implement it yourself with
> ROUTER.  The way I think of ROUTER is exactly like the hardware device
> of the same name, you tell a router's send() where to send the data,
> when you recv(), it tells you where it came from.  given that
> information you can track your own requests and timeouts for every
> given connected peer yourself in a zmq_poll() loop.
>
> -Michel
>
> On Tue, Mar 27, 2012 at 4:35 PM, Andrei Zmievski <andrei at zmievski.org>
> wrote:
> > Michel,
> >
> > Thanks for the example. However, from what I understand, this pattern
> does
> > not allow process A to re-send the request in case it has not received
> the
> > response after a certain amount of time, because REQ sockets don't allow
> > multiple messages?
> >
> > -Andrei
> >
> >>
> >> You can use non-blocking ROUTER on a poll loop and REQ or REP on the
> >> other end, that way you can handle requests and their responses as
> >> they come and as you compute them, respectively.  Whether to use REQ
> >> or REP only matters for whichever end starts the conversation.
> >> The LRU pattern documented in the guide has a good implementation of
> >> this pattern with REQ->ROUTER->REP.  It doesn't sound like you need
> >> the actual LRU part of the pattern, just the ROUTER->REQ part.  See
> >> the code for an example how to use a ROUTER socket in non-blocking
> >> mode in a poll loop to handle out of order patterns like A then B
> >> requests but you respond B then A.
> >> Start here and read it a few times. :)
> >>
> http://zguide.zeromq.org/page:all#Least-Recently-Used-Routing-LRU-Pattern
> >> -Michel
> >
> >
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