[zeromq-dev] Clean shutdown of malamute client zactor in python binding?

[Michal Vyskocil]

Hi,

In czmq things are stopped when zsys_interrupted is 1. This apply for
malamute as well. It is modified by default signal handler, so simple
ctrl-c ends your client cleanly, even if in recv call.

I assume that the default signal handler of camp is not setup correctly in
your case. Consult zsys man page for details.
Dne 3. 2. 2016 6:07 PM napsal uživatel "Aaron Sokoloski" <
asokoloski at gmail.com>:

> Hi folks,
>
> I'm trying to make the python malamute binding as easy to use as
> possible.  I'm having trouble making sure that everything gets cleaned up
> correctly on exit, though, when the client is running in a thread other
> than the main thread, and the client is blocking on a call to recv (aka
> mlm_client_recv).
>
> So far, I have something that works, but isn't ideal, which is to create a
> "shutdown" inproc socket pair whose only purpose is to notify the recieving
> end when the process gets interrupted, using a python signal handler.  Then
> the application code can poll both that receiving socket and the malamute
> client msgpipe, and exit the receive loop when it gets a message on the
> shutdown socket.
>
> Here's the gist of that approach:
> https://gist.github.com/asokoloski/02ab5affeca9be2bebdb
>
> Although conceptually simple, this is a bit awkward, especially for
> application code that may want to create multiple clients.  So what I'm
> trying to do is figure out a way to make everything get cleaned up
> automatically.  Ideally, what would happen is that the zactor thread
> finishes whatever it was doing and the zactor gets destroyed, then an
> exception is raised in the python thread.
>
> Destroying the zactor from another thread is a big no-no, because zeromq
> sockets are not thread safe, correct?  So the thread that is doing the recv
> has to wake up.  We could terminate the context directly, which would make
> the recv return, but that's quite abrupt, and doesn't give the zactor a
> chance to shut down.  We could make the recv call poll the socket
> internally, periodically waking up to check if it's been interrupted, but
> that seems gross, especially as it would have to poll rather quickly -- the
> shutdown timeout is 200ms.
>
> One options is to take the same approach of having a shutdown socket pair,
> but try to hide it inside the python library code.  Maybe the application
> code just calls recv(), but inside recv() the object polls the two
> sockets.  But that doesn't really play nicely in the case where, say, the
> application code wants to poll the malamute client and some other sockets
> at the same time.  It's doable, but feels complicated.
>
> So I have lots of questions now.  Is my reasoning above valid?  Is this
> sort of thing a problem with pure c programs as well?  Does it even matter
> if the zactor shuts down cleanly, aside from avoiding ugly warnings?  Is
> there another approach that I haven't even considered?
>
> If there isn't a better way to do this, I can bite the bullet and make the
> application code handle it, but it sure feels a bit lacking.
>
> Thanks in advance for any help anyone can offer,
> Aaron
>
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