[zeromq-dev] Breaking blocking in a server app

[Matt Weinstein]

Brian et al,

Just a followup on my comment earlier:

I look at ØMQ as enabling richer computational topologies / event- 
driven models.

So if you look at your problem, it's not a "shutdown" problem, but  
rather another event occurred ("shutdown") which triggers a different  
branch.

If you generalize the model a bit, you might end up with an interface  
that wraps poll() + recv(ZMQ_NOBLOCK) into a tidier interface (no  
flames please :-) ):

int index = zmq_recv_next({your favorite way of building a list of  
sockets});

switch (index) {
case 1:	// normal socket
	...
	break;
case 2:	// shutdown socket
	...
	break;
default: // ouch
	...
}

You could add, e.g. a command socket:

case 3: // report status
		...
		break;

If you wanted to, or simply re-use the broadcast node of case 2 to  
carry more than one "command".

This should extend gracefully to a full message-passing paradigm if  
you want  (see some of the previous posts et al), but this  
functionality should suffice for the case you described.

Best,

Matt

On Jul 1, 2010, at 3:15 PM, Matt Weinstein wrote:

> One simple way might be to use an inproc: PUB/SUB socket:
>
> 	zmq::socket_t kill_me(*ctx, ZMQ_SUB);
> 	kill_me.setsockopt(ZMQ_SUBSCRIBE, "", 0); // [typographic  
> correction applied-MW]
>
> Service threads would then poll() both their normal socket and the  
> "kill" socket.  As soon as a message arrived, the thread would  
> cleanup and quit.
>
> On Jun 30, 2010, at 9:05 PM, Brian Granger wrote:
>
>>
>>
>> On Wed, Jun 30, 2010 at 5:27 PM, Matt Weinstein <matt_weinstein at yahoo.com 
>> > wrote:
>> Under what circumstances do you want to break blocking?
>>
>> E.g. timeout, connection failure, etc.?
>>
>>
>>
>> For us, we want to do this when we want to kill a process that is  
>> sitting there blocking in zmq.recv.  IOW, we want SIGINT to trigger  
>> the process to shutdown in a semi-clean manner (no seg faults!).
>>
>> Cheers,
>>
>> Brian
>>
>> On Jun 30, 2010, at 10:23 AM, Derek Developer wrote:
>>
>>> Is there any way to break the blocking of zmq_recv() without  
>>> firing up a client and sending a message like "QUIT SERVER"?
>>>
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>>
>>
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>>
>>
>>
>> -- 
>> Brian E. Granger, Ph.D.
>> Assistant Professor of Physics
>> Cal Poly State University, San Luis Obispo
>> bgranger at calpoly.edu
>> ellisonbg at gmail.com
>> _______________________________________________
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>> http://lists.zeromq.org/mailman/listinfo/zeromq-dev
>

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