[zeromq-dev] Newbie question

[Matt Connolly]

Hi Howard,

Welcome to the list.

Have a look at figure 32 which uses a router on both sides. In that example, messages are sent to workers on a least recently used basis. You could alter this to send messages to the worker who is known to be servicing that client.

Another approach may be to have the clients talk directly to the servers and have a “dealer” simply let the client know which worker they should talk to directly, so the client then opens a new socket and connects to that worker directly. This may not fit your network though.

Regards,
Matt.

On 12 Oct 2013, at 4:53 am, Howard <howard at renci.org> wrote:

> Hi all
> 
> I hope you will forgive a newbie question. Please feel free to send me to a different resource if this question is in the wrong forum.
> 
> I've been teaching myself zeromq in combination with protobuffers.  I've been using the request/reply sockets and it's working perfectly in my simple test codes. But now I need a slightly more complicated pattern and I'm not quite sure how to do it. Here is my situation:
> 
> On one side I have a short lived client program with I would like to connect to a server.  Because there can be a few of these simultaneously I would like my server to be multi-threaded.  The situation is similar to Figure 20 in http://zguide.zeromq.org/page:all.  So far so good.  The issue however, is that I want each of my clients to interact with the same server thread over the life of it's invocation.  This is because the threads of the server are interacting with a stateful resource and multiple transactions between client and server are required to complete an operation. From what I understand of zeromq, it seems to me that I want either to
> Have the dealer make sure it forwards each request from a particular client to the same worker thread.  Is there a recommended technique for this?
> Have each client socket connect directly to a socket in the worker thread using some pattern that I don't see in the documentation. It seems possible to me that this idea is antithetical to the zeromq paradigm, so I wonder if I have some fundamental misunderstanding of zeromq or if I just missed something or maybe both.  Well, I did say I was a newbie. :)
> Rethink the idea that each client should only communication with the same thread.  I'm not sure if this is a possibility, but if 1 and 2 are difficult, I may want to investigate this further. At the least, I need each worker thread to understand which client thread it is communicating with.  I suppose I could put some type of session key in the message protocol if I knew how to get this info from zeromq.
> Any comments or suggestions (even RTFM with a pointer to the correct section) would be greatly appreciated.
> Thanks
> Howard
> -- 
> Howard Lander
> Senior Research Software Developer
> Renaissance Computing Institute (RENCI) 
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