[nanomsg] Re: Asynchronous (raw) sockets in nanomsg
- From: Martin Sustrik <sustrik@xxxxxxxxxx>
- To: nanomsg@xxxxxxxxxxxxx
- Date: Mon, 18 Nov 2013 20:59:39 +0100
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On 18/11/13 20:55, Paul Colomiets wrote:
> You have same error here. You almost certainly never want to get
> the value on the stack in asynchronous loop, since return from this
> code causes pointer to be invalidated. Your code makes sense only
> when you do a single/multiple requests without falling back to the
> main loop. And in this case you almost certainly want the cancel
> callback, so you can cancel request before ``return``ing this
> function (e.g. in case of some error between nn_send and nn_recv)
It was just a quick and dirty example, don't take it too seriously :)
>>> 2. How to know that request is timed out?
>>>
>>> rc = nn_req_recv(s, &context, buf, sizeof(buf), 0); if(rc < 0
>>> && errno == ETIMEDOUT) { printf("request %d timed out\n",
>>> *context); }
>>>
>>> Is it ok that context is filled even if error code received?
>>> Probably only certain errors will have request id filled in?
>>
>> Looks ugly, but it's technically viable.
>>
>
> kinda, yes
>
>> The other option, of course, is not to have timeouts and let the
>> use cancel the requests:
>>
>> nn_req_cancel (s, &context1);
>>
>
> That would:
>
> 1. require every user to implement timeout management
>
> 2. will leak memory since many users will forget about that
>
> The #1 is likely be easy when using some async main loop. But is
> ugly when you have a blocking code which just run multiple
> requests simultaneously.
>
> I.e. I'm almost certain that both timeout and cancel are needed.
Yes, I think you are right.
Martin
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