[zeromq-dev] [jzmq] xreq/xrep sockets and thread safety

[Matt Weinstein]

The DEVICE service thread is not designed for processing "stuff".

One design: two threads on your side -- one which is an async request  
thread (unless you get some form of signal) and an async response  
handler.

[ clients ] [ REQ ] == [ XREP ]  == [ DEVICE ] + 2 streams:

   ==> [ ZMQ_PUSH ] == [ ZMQ_PULL ] [ ASYNC_REQUESTER ]
   <== [ ZMQ_PULL ] == [ ZMQ_PUSH ] [ ASYNC_HANDLER ]

I'm presuming the async API can efficiently share state between the  
two ASYNC_* threads.

What are you actually making requests to...?

Use zmq_reactor to build DEVICE (use the poll_items branch).


On Aug 12, 2010, at 1:09 PM, Alexey Ermakov wrote:

> Hi everyone,
>
> I'm trying to figure out how to deal with the thread safety  
> restriction of 0MQ sockets. As I understand, they are bound to a  
> thread, which means that I write/read to the same socket from  
> multiple threads (which is possible with Java Posix socket  
> wrappers). I'm trying to figure out how to implement a rather simple  
> task and I can't think of a decent solution.
> My application is a Scala-based server that has an XREP socket,  
> processes the requests, and replies back. The catch is that request  
> processing is implemented by forwarding a request to another service  
> using an asynchronous API. How am I supposed to send the replies  
> back, if the XREP socket is bound to the thread that is basically  
> blocked on "while (true) socket.recv()"? I suppose I could do a 50ms  
> poll on the socket and then process the replies (fetching them from  
> a LinkedBlockedQueue or something), but that would be inefficient,  
> because requests/replies happen much less frequently. Another  
> solution would be replacing all inter-thread communication with 0MQ  
> sockets and doing a poll() on these sockets in the request handler,  
> but that doesn't sound very nice.
> Is there an easier solution I'm overlooking?
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