[zeromq-dev] How to safely use a socket in multiple threads in zmq 2.1.11

[Stephen Hemminger]

On Wed, 4 Jul 2012 19:24:21 -0300
Thiago Cangussu <cangussu at gmail.com> wrote:

> Hi,
> 
> I have a pool of threads that needs to send messages to a zmq socket. I was
> creating the socket, connecting, sending the message and closing it for
> each message, but it is for sure not an optimal usage of resources, since
> if I create/close sockets too fast, zmq is not able do release them as fast
> and I get the error: "too many open files (signaler.cpp 330)". Since I have
> no control over those threads, I'm about to try the following solution:
> 
> 1 - create a pool of connected sockets (REQ, inproc)
> 2 - when a client thread wants to send a message, it grabs a socket from
> the pool
> 3 - the thread performs a send/recv
> 4 - the thread releases the socket (which will be again available in the
> pool)
> 
> The question is: what should I do to make this multi-threaded usage of
> sockets safe? Is it enough to guarantee that multiple threads do not
> perform send/receive simultaneously?
> 
> Thanks,
> Thiago

You can have a per-thread pool of sockets, but you can't create socket
in one thread and then use it in another. Can you just have one socket
per thread in thread local storage?