[zeromq-dev] Sharing socket safely between threads

[Thomas Rodgers]

No, not really. I have designed my zmq based systems to either -

* orchestrate connections over the inproc transport
* performed the delicate dance of explicitly passing a fresh socket to a
fresh thread the way that czmq actors <http://czmq.zeromq.org/manual:zactor>
work,
  as implemented in azmq
<https://github.com/zeromq/azmq/blob/master/azmq/detail/actor_service.hpp>

On Mon, May 7, 2018 at 11:58 AM, Attila Magyari <atti86 at gmail.com> wrote:

> This sounds promising. My concern is if there are some background threads
> internally in the ZMQ library, which would use the socket out of sync with
> mine, or anything else that I'm not thinking about. I can ensure that the
> socket won't be used from multiple threads.
>
> Do you have any experience with this, or only theory?
>
> Thank you,
> Attila
>
>
> On Mon, May 7, 2018 at 5:49 PM Thomas Rodgers <rodgert at twrodgers.com>
> wrote:
>
>> The zmq docs say you need to ensure a ‘full fence’ a mutex is one way of
>> achieving that.
>>
>> If you are using C++ (-std=c++11 or later) and you can guarantee there is
>> no racy usage from another thread, you can issue a memory fence using -
>>
>> std::atomic_thread_fence
>>
>> On Mon, May 7, 2018 at 8:42 AM Attila Magyari <atti86 at gmail.com> wrote:
>>
>>> Hello,
>>>
>>> I know that zmq sockets are not thread safe. However I can't think of a
>>> good design (explained below) without using the socket in several threads.
>>> What I want to do is connect the socket in a thread, and then use it in a
>>> different one until the end, and never in parallel between several threads.
>>> I will guard the access with a mutex as well. Do you think this will be
>>> safe?
>>>
>>> Just in case someone might have a better idea for my design, here is
>>> what I'm trying to do:
>>> I have an application which starts another process, passes a port to the
>>> newly created process, so it can connect back to the main application
>>> through a ZMQ_PAIR socket. Both processes are local to the machine. The
>>> main application will request from the second one, but the second one can
>>> initiate messages without an explicit request as well. Do you have a nicer
>>> design to achieve something like this?
>>>
>>> Thank you in advance!
>>>
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>
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