client1/client2/... ==> xreply/xrequest(zmq_device) ==>
multi-worker(threads)
I think zmq_device(ZMQ_QUQUE, xreply, xrequest) is what your need.
On 2010-12-19 9:10, Dr Tune wrote:
Hi all,
Firstly,
ZMQ + protocol buffers = awesomeness, thanks! Now I can mix Java and
c++ and it all Just Works.
Secondly;
I have a server which has a single thread listening on an XREP socket
and distributing incoming requests to a pool of worker threads which
process msgs and return a result.
My issue is that b/c I can only use the ZMQ socket in the thread that
created it, the listen/distribute thread must also be the one that
returns the replies, hence I have a loop like this;
1) Poll XREP socket for new messages (non-blocking)
2) If new message, give it to a worker thread (and pass it a handle to
a threadsafe queue we have for replies
3) Check reply queue and send() any on the XREP socket
4) if no messages sent or received, sleep for 1ms
5) loop to 1
The problem being that this loop spins needlessly b/c I can't block on
step 1 or step 3; blocking on the XREP means any replies won't get
sent until next request, blocking on 3 can obviously slow things down
ridiculously.
I could slow down the spin by increasing sleep in step 4, but that
just adds latency to everything.
Obvious solutions would be;
a) if sockets were threadsafe, pass the socket instead of a queue and
allow each worker thread to write its XREP as soon as it's done. Then
you get rid of steps 3/4 and make step 1 block.
b) run a separate thread for getting queue replies and writing to
XREP, this could block on the queue, but then I'd be using my XREP
socket from two threads.
One workaround I can think of is to disregard the XREQ/XREP thing, use
two threads, open a PULL socket on one thread an a PUSH for replies on
the other. This sucks for a number of reasons not worth going into.
I seem to be solving this wrong. What's the right way to do this?
Many thanks,
DrTune
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