[zeromq-dev] Common Lisp pzmq recv-string on inproc blocks other threads

Lucas Hope lucas.r.hope at gmail.com
Tue Sep 24 00:13:51 CEST 2013

Hi there,

What happens if you add a (sleep 1) just before making the new thread?
Also, what lisp implementation are you using?

I don't have familiarity with the pzmq lisp binding. If you like, though,
you could also try the cl-czmq <https://github.com/lhope/cl-czmq> binding I


On Mon, Sep 23, 2013 at 9:42 AM, Alexander Pugachev <
alexander.pugachev at gmail.com> wrote:

> Hi,
> I am using ZeroMQ 3 with Common Lisp library pzmq. I am trying to send a
> message to server part of inproc PAIR in the main thread from client side
> of PAIR in a thread derived from main. It looks like recv-string operation
> blocks both threads at the same time while poll does not.
> recv-string basically call msg-init, then calls msg-recv until ZMQ_RCVMORE
> is returned by getsockopt(). It's ok that it blocks, I just do not
> understand why it blocks other thread.
> This code
> (defun a(endpoint)
>>   (pzmq:with-socket socket :pair
>>     (log:info "in thread")
>>     (pzmq:connect socket endpoint)
>>     (log:info "connected")
>>     (pzmq:send socket "test")
>>     (log:info "sent")))
>> (defun simple-inproc-test()
>>   (let ((endpoint "inproc://s"))
>>       (pzmq:with-socket socket :pair
>> (pzmq:bind socket endpoint)
>> (log:info "bound")
>>  (bt:make-thread (lambda () (a  endpoint))
>> :name "the-thread")
>> (log:info "before recv-string")
>>  (log:info (pzmq:recv-string socket))
>> (log:info "after recv-string!")))))
> logs only
> <INFO> [02:13:51] hi tmp.Osy6Ca (simple-inproc-test) - bound
>>  <INFO> [02:13:51] hi tmp.Osy6Ca (simple-inproc-test) - before recv-string
> and when I terminate main thread (running function simple-inproc-test) I
> see "<INFO> [02:13:54] hi tmp.CTSEWq (a) - in thread"  and then obciously
> child thread dies when it tries to send a message in the socket without
> running server side.
> If I replace the recv-string line with polling loop returning on first
> occurence of POLLIN in the socket I successfully receive the message:
>       (pzmq:with-poll-items items (socket)
>> (loop
>>    (pzmq:poll items)
>>    (when (member :pollin (pzmq:revents items 0))
>>      (log:info (pzmq:recv-string socket))
>>      (return))))
> I was trying to play with parameters of context, sockets and was trying to
> create sockets in different contexts and in the same context passed to new
> thread function - it is all the same, and now I think this is some ZeroMQ
> principle I haven't read or understood.
> Am I doing something completely wrong? How blocking receive operation in
> one thread can block other thread as well?
> Thanks, Alexander.
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Dr Lucas Hope - lucas.r.hope at skype
Machine Learning and Software Engineering Consultant
Melbourne, Australia
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