Using ZeroMQ in a PHP script inside Apache

Question

I want to use the ZeroMQ publisher/subscriber to dispatch data from my web application to multiple servers.

I use Apache and PHP for the web app, my php script works as follow:

//Initialization
$context = new ZMQContext();
$publisher = $context->getSocket(ZMQ::SOCKET_PUB);
$publisher->bind("tcp://*:5556");

//Then publishing for testing:

$publisher->send("test");
$publisher->send("test");
$publisher->send("test");
$publisher->send("test");
$publisher->send("test");

For testing I adapted a subscriber from the documentation in python:

import sys
import zmq

#  Socket to talk to server
context = zmq.Context()
socket = context.socket(zmq.SUB)

socket.connect ("tcp://localhost:5556")

# Subscribe to zipcode, default is NYC, 10001
socket.setsockopt(zmq.SUBSCRIBE, "")

print "Waiting..."
# Process 5 updates
for update_nbr in range (5):
    string = socket.recv()
    print string

The whole thing works when I run the php script from command line but does not work through Apache (when the script is run through a web browser).

Is there anything I should do to my Apache configuration to make it work ?

Thanks

Alexandre

Answer 1

It seems that the only problem was that the connection didn't have time to be established.

Adding a sleep on the publisher after the binding and before the send did resolve the issue, even though not quite elegantly.

The issue is explained here:

http://zguide.zeromq.org/page:all#Getting-the-Message-Out