[zeromq-dev] level-triggered FD

[MinRK]

On Fri, Jan 22, 2016 at 5:30 PM, Doron Somech <somdoron at gmail.com> wrote:

> the FD must be read-only, it might be possible in some OS but I won't be
> portable.
>
> Regarding the Command FD, it must be used, otherwise the Recv/Send FD
> won't work.
>
> So in your case you need to be add the event-loop both the command FD
> (which is the regular FD) and Recv/Send FD.
>
> When command FD is signaled you must call zmq_process_comands, which
> currently doesn't exist.
> When recv/send FD is signaled you can call recv/send.
> zmq_process_command it what causing the other FDs to get signaled.
>
> The bottom line, this is kind of syntactic sugar, it will be the
> equivalent of calling has_in or has_out immediately after FD is signaled
> and only then call recv/send.
>

Gotcha, thanks for the explanation. I think this will still be a huge
improvement.

-MinRK


>
>
>
>
>
> On Fri, Jan 22, 2016 at 5:54 PM, MinRK <benjaminrk at gmail.com> wrote:
>
>>
>>
>> On Fri, Jan 22, 2016 at 4:19 PM, Doron Somech <somdoron at gmail.com> wrote:
>>
>>> The FD today is signalled when ever a command should be processes. What
>>> we can do is split it to 3 different FD:
>>>
>>> * Command FD : The one being used right now, this still must be used,
>>> when ever signalled call process commands (which we should expose in API).
>>> * Recv FD: use as level triggered to receive.
>>> * Send FD: use as level triggered to send.
>>>
>>> Only issue with this solution, you should include in your event loop
>>> minimum two FD, one for processing commands and one for send/ recv.
>>>
>> I think two FDs would be fine; certainly better than what we have now. It
>> would eliminate the significant problem of one signal for separate events.
>> Perhaps this is a naïve question: Is it not possible to have an FD signal
>> writable when the socket becomes writable and readable when the socket
>> becomes readable? If they both have to be read-only FDs, that seems fine,
>> as long as the signaling for send and recv are separated somehow. I'm not
>> sure what users would do with the Command FD.
>>
>> -MinRK
>>
>>
>>> For thread safe sockets this is a little simpler as we can make one FD
>>> for all sockets for processing commands.
>>> On Jan 22, 2016 2:52 PM, "Pieter Hintjens" <ph at imatix.com> wrote:
>>>
>>>> Yes, the edge triggered FD in libzmq has been a constant source of
>>>> annoyance. Maybe someone on this list knows how to fix it.
>>>>
>>>> On Fri, Jan 22, 2016 at 1:40 PM, MinRK <benjaminrk at gmail.com> wrote:
>>>> > Hi all,
>>>> >
>>>> > I've implemented yet another eventloop integration in pyzmq (asyncio,
>>>> this
>>>> > time), and this is only nontrivial because of the edge-triggered
>>>> read-only
>>>> > zmq.FD. Integrating into existing eventloops would be much easier if
>>>> we had
>>>> > a more traditional level-triggered FD to work with.
>>>> >
>>>> > Is there a technical reason why we can't add a zmq.LEVEL_FD that would
>>>> > behave in a more conventional manner:
>>>> >
>>>> > - level-triggered
>>>> > - signal write when socket is writable
>>>> > - signal read when socket is readable
>>>> >
>>>> > I would work on this myself, but unfortunately I don't think I have
>>>> the
>>>> > relevant expertise.
>>>> >
>>>> > -MinRK
>>>> >
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