Hi Itay:
Take a look at https://github.com/zeromq/libzmq/issues/3186
<https://github.com/zeromq/libzmq/issues/3186> — it may be relevant to the
behavior you’re seeing.
The short version is that process_commands needs to get a chance to run on the
socket to clean up resources. If that isn’t done, resources (in this case
memory, but in your case potentially fd’s) can appear to leak until the context
is shut down.
Hope this helps…
Bill
> On Dec 29, 2020, at 7:12 AM, Itay Chamiel <itay.cham...@orcam.com> wrote:
>
> Hi, we have a client thread that is supposed to receive data from a parent
> thread, then disconnect when done. We've noticed that when the socket is
> closed there's a leak of an eventfd (file descriptor), therefore we have a
> leak every time such a client is created and destroyed - even if no data is
> transferred.
>
> Here is a quick C++ program to reproduce it. I'm running on a Ubuntu 18
> desktop with ZMQ 4.1.6 or 4.3.3. This loop is expected to run forever but
> crashes a little after 1000 iterations due to too many open files.
>
> #include "zmq.hpp"
>
> int main() {
> zmq::context_t context;
> while(1) {
> zmq::socket_t* socket = new zmq::socket_t(context, ZMQ_SUB);
> socket->connect("inproc://some_name");
> delete socket;
> }
> }
>
> The problem does not occur for other connection types (i.e. replace inproc
> with ipc and the problem will not occur).
> In case you want it without the C++ bindings, here is a slightly more
> elaborate C example which also sets LINGER to zero (with no effect) and
> displays the number of FDs in use by the process each iteration.
>
> #include <zmq.h>
> #include <stdlib.h>
> #include <sys/types.h>
> #include <unistd.h>
>
> int main() {
> void* ctx = zmq_ctx_new();
> for (int i=0; ; i++) {
> void* zmq_sock = zmq_socket(ctx, ZMQ_SUB);
> if (!zmq_sock) { printf("fail after %d iterations: %s\n", i,
> zmq_strerror(errno)); exit(-1); }
> int linger = 0;
> int rc = zmq_setsockopt(zmq_sock, ZMQ_LINGER, &linger, sizeof(linger));
> // this doesn't actually help
> if (rc != 0) exit(-1);
> rc = zmq_connect(zmq_sock, "inproc://some_name");
> if (rc != 0) exit(-1);
> rc = zmq_close(zmq_sock);
> if (rc != 0) exit(-1);
> // show the number of used FDs
> char cmd[100];
> sprintf(cmd, "ls -l -v /proc/%d/fd | wc -l", (int)getpid());
> system(cmd);
> // test is hard to abort without a sleep
> usleep(100*1000);
> }
> }
>
> Thank you,
>
> Itay Chamiel, OrCam
>
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