Hi Jay,
czmq will create the context for you whenever you touch the sockets. So
as you already figured out fork before using czmq sockets. I cannot
recommend using zsys_shutdown() to force destruction of the context as
there might be side effects. What's your use case anyhow?
//Kevin
On Mi, Dez 21, 2016 at 10:42 , Jay Rolette <[email protected]> wrote:
> If I call zsys_shutdown() in the child process immediately after
the fork (or, at least, before I try to do anything else with czmq),
then czmq reinitializes itself, so the child gets a new context and
the IO threads are created.
>
> Still more testing needed to make sure it works reliably, but
initial tests are positive. If anyone knows of issues with calling
zsys_shutdown() like this, I'd love to hear about it.
Minor patch required to make this work. zsys_init() fails a safety
check: assert(!s_process_ctx). If I modify zsys_shutdown() to set
s_process_ctx = NULL after the zmq_term() call, then it works.
I'll see about putting together a pull request unless someone can
point me to a better answer using czmq.
Jay
On Wed, Dec 21, 2016 at 12:26 PM, Jay Rolette <[email protected]>
wrote:
Hi Kevin,
Thanks. I've read the guide and that all makes sense, but in this
case, I'm trying to use czmq as a higher-level API. In it's latest
incarnation, it doesn't expose the zmq context at all.
I'll go back and rewrite my code to just use the base zmq APIs if
necessary, but I'm hoping to stick with czmq for now.
It looks like I may have found a solution that fits within czmq...
If I call zsys_shutdown() in the child process immediately after the
fork (or, at least, before I try to do anything else with czmq),
then czmq reinitializes itself, so the child gets a new context and
the IO threads are created.
Still more testing needed to make sure it works reliably, but
initial tests are positive. If anyone knows of issues with calling
zsys_shutdown() like this, I'd love to hear about it.
Thanks,
Jay
On Wed, Dec 21, 2016 at 11:49 AM, Kevin Sapper
<[email protected]> wrote:
Hi Jay,
this is for you
http://zguide.zeromq.org/page:all#Getting-the-Context-Right
//Kevin
On Mi, Dez 21, 2016 at 4:49 , Jay Rolette <[email protected]>
wrote:
I recently started using czmq and have run into a problem with the
global zmq context it uses when the process forks...
If the parent process does anything to cause the global context to
be created prior to forking, the child process is unable to
send/recv messages. That's not too surprising since zmq contexts
aren't shareable across processes, but I've been looking through
the czmq code for a way to destroy/recreate the global context in
the child process and not finding an obvious way to do that.
In older versions of czmq, it looks like I probably could have
used zctx_* calls to create a new context, but those were removed.
Not seeing anything similar in zsock_* or zsys_*.
Details about the behavior I'm seeing in the child process:
zmsg_send() returns success, but nothing is received on the server
side. On the client, the subsequent call to zmsg_recv() never
returns.
This is on Ubuntu 14.04 LTS, czmq 4.0.1, libzmq 4.2 with pretty
basic REQ/REP sockets.
Is there anyway to stick with czmq for this or do I have to back
off to vanilla zmq?
Thanks,
Jay
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