[zeromq-dev] Communication between two threads

gonzalo diethelm gdiethelm at dcv.cl
Fri Mar 19 15:24:19 CET 2010

> I've got lost in the scenario :) Can you write down few points showing
> step-by-step what your application should do?

Ok, sorry for the rant. It is like this.

My process will have two threads. One of them, called "poller", owns and
has several sockets open, and issues an infinite poll() loop on all of
them. This way I can react to incoming requests, to notifications the
process is subscribed to, etc.

The second thread, called "runner", does "real work". It is computing
things, reading / writing to a DB, etc.

Some times I need to send a message, from the runner thread, over one of
my sockets in the poller thread. This is because I want to notify
another process about something, or I want to request some information
from an external process.

Since poller and runner are separate threads, and I can only use the
sockets in the poller thread, I thought about doing this:

1. Add an inproc REP socket, called "pipe", to the poller thread, and
put it in the poll loop.
2. Add an inproc REQ socket to the runner thread, connected to "pipe".
3. When the runner thread needs to fire off a message, it writes it to
its inproc REQ socket and busy-waits for a reply.
4. The poll loop wakes up in the poller thread, reads a message from the
inproc REP socket, sends it over the "real" outgoing socket, waits for a
reply and sends this reply back over the inproc REP socket.
5. The runner thread receives its answer back and goes merrily about
working with it.

Besides allowing me to do all external communications from a single
thread, this setup neatly solves the synchronization between the two

Is this recommended in 0MQ architectures? Maybe even common practice?
Are there any performance issues I should be concerned about inproc

Thanks again.

Gonzalo Diethelm

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