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

[Harry Mander]

Hi Bill,

Thanks for pointing me towards that - looking at the other issues linked in
that report it seems this is a long standing issue with ZMQ...
Unfortunately sending dummy messages, getting `ZMQ_EVENTS` with
`zmq_getsockopt`, or calling `zmq_poll` on the PUB socket immediately after
a message is sent still doesn't fix the issue even after SUB sockets are
closed. I will keep digging...

On Thu, 5 Nov 2020 at 02:56, Bill Torpey <wallstprog at gmail.com> wrote:

> Hi Harry:
>
> Not sure if this is relevant, but we had a similar-sounding problem —
> check out https://github.com/zeromq/libzmq/issues/3186 and see if it
> might be helpful.
>
> Regards,
>
> Bill
>
>
> 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
> Subscriber minimal test case, min-sub: 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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-- 

*Harry Mander*
*Junior Design Engineer*Tait Communications
Email: harry.mander at taitradio.com


www.taitradio.com

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