[zeromq-dev] Load balancing and fault tolerance

[Brian Granger]

On Tue, Jul 13, 2010 at 10:02 PM, Martin Sustrik <sustrik at 250bpm.com> wrote:
> Brian Granger wrote:
>
>>> I would say the whole retransmission part has to be inside of 0MQ rather
>>> than implementing in on top of it.
>>>
>>> I like to think about XREQ/XREP as an equivalent of IP in the Internet
>>> stack. You send data. Presumably they get to the destination, however,
>>> they
>>> may get lost occasionally.
>>>
>>> Therefore, there's a reliability layer on top of it: REQ/REP (or TCP in
>>> case
>>> of Internet stack) which monitors the replies (ACKs) and in case of
>>> problem,
>>> manages the retransmission.
>>
>> Are you suggesting then that all of this be transparently happens
>> inside the 0MQ library, so that I don't have to worry about this?
>
> Yes. The functionality should be definitely part of 0MQ library in the
> future. Reliable delivery is one of the big value-adds of MQ-style solutions
> after all.

That would be extremely nice.  With that, our entire infrastructure
could be handled by a simple ZMQ_QUEUE device!

>> That would be quite nice!  That would require an XREQ socket to buffer
>> all messages until it knows they have been handled.  The only odd
>> thing about the picture is that IP ensures only that packets get
>> there, not that the other side replies.  In this case, I want to be
>> sure that I actually get the reply from the other side.
>
> Think of TCP rather than IP. It actually solicits the reply from the peer
> (ACK), however, it's kind of invisible to the user as there are no user data
> bound to the reply.

Yes, OK now I see what you mean.

Cheers,

Brian

> Martin
>
>



-- 
Brian E. Granger, Ph.D.
Assistant Professor of Physics
Cal Poly State University, San Luis Obispo
bgranger at calpoly.edu
ellisonbg at gmail.com