[zeromq-dev] REQ/REP newbie question

Jeremy Selan jeremy.selan at gmail.com
Sat Sep 1 03:51:27 CEST 2012

Thanks for the pointer. Dealer/router looks like exactly what I'd like
to use. Thanks!

On Fri, Aug 31, 2012 at 12:46 PM, Amr Ali <amr.ali.cc at gmail.com> wrote:
> Have you tried to use DEALER/ROUTER pattern (used to be called XREQ/XREP)?
> I'd like to think of DEALER/ROUTER as the primitive for REQ/REP as it doesn't
> constrain you having to reply to every request but of course you'll have to
> manage socket IDs yourself to know whom to reply to only if needed.
> On 08/31/2012 09:21 PM, Jeremy Selan wrote:
>> From a newbie zmq user...
>> I am using zmq to stream a series of queries/updates from a user interface to an
>> underlying data model (using the ipc mechanism).
>> Some of these messages - representing queries - are
>> conceptually synchronous where the response is required.  And some of these
>> messages - the push updates - are asynchronous (where the response value, an
>> empty buffer, is ignored.
>> I am currently using a single req/reply pattern for both the queries and the
>> updates. This is obviously not ideal for performance, as it requires a needless
>> round-trip for the update messages.
>> I experimented with using two connections, req/rep along with push/pull, using
>> the poller to do interleaved handling.  However, while this correctly models the
>> message handling, the message handling no longer preserves ordering as it uses
>> two independent sockets.
>> While I could add a higher level mechanism to replicate the ordering,
>> the simplicity of using a single zmq socket to preserve inherent message order
>> is appealing.
>> Is there a way to do req/rep where you can tell zmq to not expect
>> reply? (Something like a send flag, "NO_RESPONSE_EXPECTED", for req/rep.)
>> Is it possible to point both the req/rep and the push/pull at the same socket to
>> achieve a similar effect, which does preserver ordering?
>> Or an alternative best practice?
>> Thanks!
>> -- Jeremy
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> --
> Amr Ali
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