[zeromq-dev] Send queue after socket close

[Pieter Hintjens]

Right. That kind of handshake seems necessary even using plain TCP.

On Tue, Jan 14, 2014 at 4:16 PM, Lindley French <lindleyf at gmail.com> wrote:
> I'm using zmqpp, which in turn appears to use the libzmq API.
>
> I'm still not sure exactly what was going on, but the THANKS message
> approach seems to have fixed the immediate problem.
>
>
> On Tue, Jan 14, 2014 at 10:07 AM, Pieter Hintjens <ph at imatix.com> wrote:
>>
>> Ah, the default is indeed -1, meaning infinite linger, and no message
>> loss.
>>
>> If you use CZMQ it defaults to 0.
>>
>> Are you using CZMQ or the native C API? The DEALER close should wait
>> until all messages are sent.
>>
>> Still, I'd not trust it; even "sent" can mean "delivered to socket
>> layer but still in transit".
>>
>> -Pieter
>>
>> On Tue, Jan 14, 2014 at 3:29 PM, Lindley French <lindleyf at gmail.com>
>> wrote:
>> > Perhaps I misinterpreted this sentence on the zmq_close() page:
>> > "The default setting of ZMQ_LINGER does not discard unsent messages"
>> >
>> >
>> > On Tue, Jan 14, 2014 at 8:47 AM, Pieter Hintjens <ph at imatix.com> wrote:
>> >>
>> >> On Tue, Jan 14, 2014 at 12:34 PM, Lindley French <lindleyf at gmail.com>
>> >> wrote:
>> >>
>> >> > According to the docs, by default if a socket is closed, its send
>> >> > queue
>> >> > will
>> >> > still be sent. However, the behavior I'm seeing casts some doubt on
>> >> > this.
>> >>
>> >> Where is this stated? Afaik the socket pipes (with messages) are
>> >> destroyed when the socket is destroyed, which will wait for the LINGER
>> >> time set on that socket, if there are messages waiting to be sent.
>> >>
>> >> > One practical solution would be for the ROUTER to send back a
>> >> > "THANKS"
>> >> > message to the DEALER once it has everything, and not allow the
>> >> > socket
>> >> > to
>> >> > close until then. I would like to understand the subtleties of the
>> >> > implementation, though.
>> >>
>> >> Indeed, that's what you'd want to do. Closing the socket will drop an
>> >> undefined messages in flight unless you set infinite linger, which can
>> >> lead to your application blocking.
>> >>
>> >> -Pieter
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>> >
>> >
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