[zeromq-dev] Maximum number of zactors?

[Arnaud Loonstra]

Thanks Doron!

I guess this post from Pieter is a good backgrounder as well:

http://hintjens.com/blog:84

On 5/16/19 7:49 PM, Doron Somech wrote:
> 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 
> <mailto: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>
>      > <mailto: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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