[zeromq-dev] RFC: PPPP - Paranoid Pirate Publishing Protocol

[Pieter Hintjens]

I believe it's been mooted before, and ZMQ_STREAM sockets do this,
sending null messages to signal when there's a new client connection
and/or a disconnected client.

On Wed, Jul 2, 2014 at 2:08 PM, Goswin von Brederlow <goswin-v-b at web.de> wrote:
> On Tue, Jul 01, 2014 at 06:23:41PM +0200, Pieter Hintjens wrote:
>> On Tue, Jul 1, 2014 at 4:46 PM, Goswin von Brederlow <goswin-v-b at web.de> wrote:
>>
>> > 1) with ROUTER/DEALER I don't get a message when a subscriber
>> > disconnects without unsubscribing.
>> >
>> > Eventualy the heartbeat will get it but that can take a long time and
>> > a lot of messages can queue up inbetween for no good reason.
>>
>> There is no other way, in practice. Even if libzmq reports the TCP
>> disconnect, there are cases where the network connection will block
>> and die without reporting an error. You must eventually use
>> heartbeats. You can tune these to a few seconds.
>
> But with tcp there is a way. And (X)PUB/(X)SUB do use it. I know it
> isn't totaly reliable since it can't catch kernel or network crashes
> in a timely fashion. But 99.999% of cases will properly close the tcp
> socket.
>
> The goal is to catch the common case early while still handling the
> exceptional one with heartbeats.
>
>> > So I tried using a monitor socket. But that only gives me the FD and
>> > address of the receiving socket:
>>
>> No use IMO.
>>
>> > 2) with XPUB/XSUB the CURVE metadata seems to get lost
>> >
>> > zmq_msg_gets() always returns Null it seems. I think the problem is
>> > that zmq::xpub_t::xread_activated just appends the message data to its
>> > internal std::deque. A ROUTER socket on the other hand attaches the
>> > pipe to its fair queue.
>> >
>> > Should this be rewritten to use a fair queue too?
>>
>> That would make sense, yes.
>>
>> -Pieter
>
> MfG
>         Goswin
> _______________________________________________
> zeromq-dev mailing list
> zeromq-dev at lists.zeromq.org
> http://lists.zeromq.org/mailman/listinfo/zeromq-dev