[zeromq-dev] Memory footprint of process bound to PUB socket increases as subscribers connect

Bill Torpey wallstprog at gmail.com
Wed Nov 4 14:56:10 CET 2020

Hi Harry:

Not sure if this is relevant, but we had a similar-sounding problem — check out https://github.com/zeromq/libzmq/issues/3186 <https://github.com/zeromq/libzmq/issues/3186> and see if it might be helpful.



> On Nov 4, 2020, at 2:54 AM, Harry Mander via zeromq-dev <zeromq-dev at lists.zeromq.org> wrote:
> Hi,
> I am having an unusual problem with memory usage and PUB/SUB sockets. Tested in C with libzmq 4.3.3 on Ubuntu 18.04.
> I have a process which is bound to a PUB socket whose memory footprint (as measured by top, htop etc.) grows as other processes subscribe to the socket with SUB. However, the memory footprint of the PUB process does not increase when the SUB sockets are closed.
> Publisher minimal test case, min-pub: https://pastebin.com/r85GZYcw <https://pastebin.com/r85GZYcw>
> Subscriber minimal test case, min-sub: https://pastebin.com/9cw7tNgL <https://pastebin.com/9cw7tNgL>
> min-pub polls stdin for messages to send on `ipc://@test` socket. Memory footprint increase can be seen on my machine by running `min-sub 100 info` which creates 100 subscribers connected to `ipc://@test` and subscribes each one to "info". Typing "info message" into min-pub causes messages to be received fine in min-sub process. min-sub is closed by sending SIGINT (i.e. Ctrl-C) before which the SUB sockets will unsubscribe from "info" and be closed. min-pub is closed by sending EOF (i.e. Ctrl-D).
> Each time min-sub is run the resident memory footprint of min-pub as observed in htop increases and never decreases even after min-sub exits. If min-sub is run enough times min-pub will be terminated by the OOM killer.
> I have tested both sub and pub programs with memcheck and neither reports any errors or memory leaks.
> Regards,
> Harry
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