[zeromq-dev] UDP without PGM

Doron Somech somdoron at gmail.com
Wed Apr 27 08:42:13 CEST 2016


It is not reliable (and currently doesn't support PGM).

It is pretty new and not yet documented, you can take a look at the test:

https://github.com/zeromq/libzmq/blob/master/tests/test_radio_dish.cpp

Few differences from pubsub:
* Exact matching (vs prefix matching of pubsub)
* Group (Topic) is null terminated string
* Group is currently limited to 16 chars (including terminating null),
should be extended in the future
* To join/leave a group you call zmq_join/zmq_leave (vs zmq_setsockopt of
pubsub)
* To set the group of a message you need to set msg group property using
zmq_msg_set_group
* It doesn't support multipart (the group is part of the message)

Hopefully will document it soon.

Doron


On Tue, Apr 26, 2016 at 5:52 PM, Utsav Drolia <utsavdrolia at gmail.com> wrote:

> Is there a document/note describing the internals for the Radio/Dish
> pattern?
> Also, when you say multicast, I am assuming it is not reliable?
>
> Thanks!
>
> On Apr 26, 2016, at 3:54 AM, Doron Somech <somdoron at gmail.com> wrote:
>
> Zeromq now have UDP transport, which you can use with the radio-dish
> socket types.
>
> No docs yet so take a look at the following test:
>
> https://github.com/zeromq/libzmq/blob/master/tests/test_udp.cpp
>
> Both multicast and unicast should work.
>
> On Tue, Apr 26, 2016 at 6:26 AM, Ben Kloosterman <bklooste at gmail.com>
> wrote:
>
>> Just leave the UDP ..  I use UDP  as a separate channel and its so
>> different that it should always be considered different eg no guarantee ,
>> no packet > 64K / MTU  etc etc Forcing it to the sane structure is likely
>> to be a bad idea.
>>
>> Ben
>>
>> On Tue, Apr 26, 2016 at 8:10 AM, TL;DR <tldr1969 at gmail.com> wrote:
>>
>>> Hi, I just wanted to kick this conversation again.
>>>
>>> Does anyone have any pointers to patches or experimental versions that
>>> provide UDP datagram transport without PGM?  Just plain UDP for
>>> unicast/multicast.
>>>
>>> I have migrated pretty much all services in a system over to ZeroMQ.
>>> But there is a use case where I use UDP today, and haven't been able to do
>>> so.  I'm thinking there must be others (esp in finance) who are in the same
>>> boat.
>>>
>>> PGM is a non-starter because auto-magical but late delivery is worse for
>>> us than no delivery in this use case.  These particular applications have
>>> more complex behavior when they have missed something, and there is a
>>> favored application level mechanism for detection of missed messages and
>>> recovery.
>>>
>>> Thanks for any advice,
>>>
>>> _______________________________________________
>>> zeromq-dev mailing list
>>> zeromq-dev at lists.zeromq.org
>>> http://lists.zeromq.org/mailman/listinfo/zeromq-dev
>>>
>>
>>
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>>
>
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