[zeromq-dev] Maximum number of zactors?

[Doron Somech]

Over inproc zeromq need to signal the other thread (if asleep, no waiting
messages) that a message is ready to be consumed. Internally zeromq is
using a file descriptor for that.

However, with thread-safe sockets, a mutex and conditional variable are
used for signaling so no file descriptor is used (and it doesn't go to the
kernel for most cases, so some way faster).

CLIENT-SERVER, RADIO-DISH, and GATHER-SCATTER are the new thread-safe
sockets. You can use them from multiple threads. However, the catch is that
they don't support multi-part messages.

In the case of zactor, we can benefit from a thread-safe actor, which can
be called from multiple threads. However, we might need to create a new
class for that, or maybe just a constructor. zactor_new_safe?

I think the CLIENT-SERVER sockets are the best fit for the safe actor. When
it is only a command threads can share the client, but when it is a
request-response we would need to create a client per thread or client per
request, which is not that expensive as no file descriptor is created.


On Thu, May 16, 2019 at 8:32 PM Arnaud Loonstra <arnaud at sphaero.org> wrote:

> Hi Doron,
>
> Can you elaborate? I've heard about threadsafe sockets in zmq but
> haven't seen them in the wild. Any pointers?
>
> Rg,
>
> Arnaud
>
> On 5/16/19 6:01 PM, Doron Somech wrote:
> > File descriptor is being used for signaling.
> > If zactor would use thread safe sockets it would be unlimited.
> >
> > On Thu, May 16, 2019, 18:51 Arnaud Loonstra <arnaud at sphaero.org
> > <mailto:arnaud at sphaero.org>> wrote:
> >
> >     Hi all,
> >
> >     I'm currently stress testing a setup with actors. What's the maximum
> >     number of running zactors? As it's using inproc no file descriptors
> are
> >     involved. I'm using this test:
> >
> >           // mega zactor test
> >           zlist_t *spawned_act = zlist_new();
> >           for (int i=0;i<507;i++)
> >           {
> >               zactor_t *act = zactor_new(echo_actor, "Hello actor");
> >               assert(act);
> >               zlist_append(spawned_act, act);
> >           }
> >           while(zlist_size(spawned_act) > 0)
> >           {
> >               zactor_t *dstr = zlist_pop(spawned_act);
> >               zactor_destroy(&dstr);
> >           }
> >
> >     If I go beyond 507 actors I receive an assert:
> >
> >     src/zsock.c:88: zsock_new_checked: Assertion `self->handle' failed.
> >
> >     Which traces back to:
> >
> >     self->handle = zsys_socket (type, filename, line_nbr);
> >
> >     Which is a wrapper for creating a zmq socket.
> >
> >     Any ideas why there's is this limit of 507 actors?
> >
> >     I also tried with my own actor library which adds pub/sub sockets to
> >     the
> >     actor. I then have a maximum of 252 actors.
> >
> >     Rg,
> >
> >     Arnaud
> >
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> >
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