[zeromq-dev] How should sockets be destroyed?

Olaf Mandel o.mandel at menlosystems.com
Mon Feb 24 11:32:14 CET 2014


Hello,

I am currently trying to open and close many sockets and run into the
MAX_SOCKETS limit, even though only one socket should be open at a time.
Basically I do (return value checks removed for readability):

int const l = 0;
int i;
for(i=0; i<10000; ++i) {
    socket = zmq_socket(context, ZMQ_REP);
    rc = zmq_setsockopt(socket, ZMQ_LINGER, &l, sizeof(l)); /* #1 */
    rc = zmq_connect(socket, "inproc://demo");
    rc = zmq_close(socket);
}

The socket creation fails in zmq::ctx_t::create_socket() at
if(empty_slots.empty ()) { /*fail*/ } .
Note 1: The presence or absence of zmq_setsockopt() makes no difference.


When trying to figure out what happens on zmq_close(), I run into
zmq::socket_base_t::check_destroy(), which never seems to do anything.
It simplifies down to the following:

if (destroyed) { // set by zmq::socket_base_t::process_destroy()
    /*destroy fd and socket, send notification to preaper*/
    zmq::own_t::process_destroy();
}

Here socket_base_t::process_destroy() is a virtual overload of
own_t::process_destroy(), and it seems to be called from a single place:
zmq::own_t::check_term_acks() . But I lack the background to understand
this if-statement which is never true:

if(terminating && processed_seqnum == sent_seqnum.get () &&
   term_acks == 0) {
   /* ... */
   process_destroy();
}


So my question boils down to: is this expected behaviour and I am doing
something wrong (like failing to call another close-function in addition
to zmq_close()) or is this a known or new bug in ZMQ?

Thanks for any insight,
Olaf Mandel

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