On Tue, 2018-12-11 at 22:07 +0000, martin.belan...@dell.com wrote: > Hi, > > I'm experimenting with zmq_socket_monitor(). I have a XSUB socket > that I'm monitoring. The monitoring works fine. I'm just trying to > understand how I can enable/disable monitoring back-and-forth by > calling zmq_socket_monitor(). > > I tried to enable/disable/re-enable monitoring by invoking > zmq_socket_monitor() as shown below I get the error "Address already > in use" on the 3rd invocation. > > 1) zmq_socket_monitor(my_xsub_sock, "inproc://starship-enterprise", > ZMQ_EVENT_ALL); > 2) zmq_socket_monitor(my_xsub_sock, NULL, 0); > 3) zmq_socket_monitor(my_xsub_sock, "inproc://starship-enterprise", > ZMQ_EVENT_ALL); <- ERROR > > I followed the source code for zmq_socket_monitor() to a method > called zmq::socket_base_t::monitor(). That function eventually calls > zmq_bind() where I believe the error occurs. > > 1) The first time zmq_socket_monitor() is called a ZMQ_PAIR socket is > created (_monitor_socket) and bound to address "inproc://starship- > enterprise". Note that this socket is created with ZMQ_LINGER=0. > > 2) The second time zmq_socket_monitor() is invoked to disable > monitoring _monitor_socket is closed and because ZMQ_LINGER=0 it > should go out of existence right away. Right? > > 3) The third time zmq_socket_monitor() is called I get "Address > already in use" as if the old socket is still there. How can that be? > > Regards, > Martin
Without looking with gdb, my best guess is a race: the close is asynchronous and non-blocking, so the third call might try to re-use the same endpoint that is still technically in use. IIRC inproc sockets events are processed from the "connecting" socket's thread, so try to run something (ie: zmq_getsockopt zmq_events) on the connecting inproc before the third call and see if that helps. -- Kind regards, Luca Boccassi
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