[zeromq-dev] Explicit patterns

Mark V mvyver at gmail.com
Tue May 25 01:28:24 CEST 2010

On Tue, May 25, 2010 at 8:04 AM, Pieter Hintjens <ph at imatix.com> wrote:
> Hi all,
> I'm writing a guide for 0MQ beginners and I've hit two problems in
> understanding and explaining 0MQ, which I think are faced by many
> people before they really know 0MQ well. The first problem is that 0MQ
> patterns, which are really important building blocks, are not 1st
> class entities.  A pattern is a set of socket types and devices but
> those names don't mention patterns at all.  There is no hint of what
> combinations of socket and device are legal.  We have to learn it all
> by heart.
> Second problem is that the socket types are irregular.  For
> request-reply they indicate the type of message a node sends.  For
> pub-sub they are the role of the node.  For paralyzed processing they
> indicate the flow of data.  For pair they indicate the nature of the
> connection.
> So it seems inevitable that people will misuse socket types and
> patterns until they learn by error.  We lack a consistent model of
> what a pattern is and how the names of things are derived.
> Here's a proposal that will fix this, we think.  We being Mato and
> myself.  It's going to hurt but it's arguably better now than later.
> We propose these consistent rules:
> * All socket types and devices names contain the pattern identifier.
> We suggest RR, PS, BF, and EP for request-response, pub-sub,
> butterfly, and exclusive pair respectively.
> * Socket and device types are named ZMQ_XX_YYYY where XX is the
> pattern identifier and YYYY is the socket or device type.
> * Socket types always reflect the role of the node, period.
> This gives us (as example, the details may change):
> * ZMQ_RR_CLIENT, ZMQ_RR_SERVER for sockets, ZMQ_RR_QUEUE for device.
> ZMQ_BF_STREAMER for device.
> * ZMQ_EP_PEER for sockets.

Thanks for making all this effort to keep 0MQ's barriers to entry low.
I did think appending _S,_D to indicate socket, device.  However, it
does clutter the names a little.
Alternatively, you could indicate the socket names are nouns and
device names are verbs (broadly).  This would suggest that the device

Not sure if sockets/devices can be characterized/categorized that way?


> Incidental change proposals are to rename parallelized process as
> "butterfly" and pair as "exclusive pair" to give these patterns more
> friendly names.
> Comments, thoughts?
> -Pieter
> (Also posted at http://www.zeromq.org/draft:explicit-patterns)
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