poblano_backend.py

#!/usr/bin/python
#
# Requires libevent, greenlet, gevent and pyzmq.
#
# Exemplar run:
#
# $ ./poblano_backend.py                                                                                             
# GitHub handled by worker 1: OK
# Jenkins handled by worker 2: OK
# Review Board handled by worker 1: OK
# Pivotal Tracker handled by worker 2: OK

import gevent
import zmq.green as zmq

# Settings.
POBLANO     = 'inproc://poblano'
POBLANO_HUB = 'inproc://hub'
WORKERS     = 2

# 0MQ context used in this example. No I/O threads since we are inproc.
ctx = zmq.Context(0)

# The Hub greenlet forward messages to workers.
def poblano_hub():
    frontend = ctx.socket(zmq.ROUTER)
    frontend.bind(POBLANO)
    backend = ctx.socket(zmq.DEALER)
    backend.bind(POBLANO_HUB)
    zmq.device(zmq.QUEUE, frontend, backend)

# The Worker greenlet just appends its ID and returns the message.
def poblano_worker(wid):
    frontend = ctx.socket(zmq.DEALER)
    frontend.connect(POBLANO_HUB)
    while 1:
        msg = frontend.recv_multipart()
        msg.append('handled by worker {0}: OK'.format(wid))
        frontend.send_multipart(msg)

# Now let's spawn our greenlets (kinda processes or threads).
gevent.spawn(poblano_hub)

# Give the hub greenlet some time to bind the socket. Specific to inproc.
print('Waiting a second for the hub process to bind properly...')
gevent.sleep(1)

for i in range(1, WORKERS+1):
    gevent.spawn(poblano_worker, i)

# Initialize the exemplar client. Send some messages and wait for the replies.
client = ctx.socket(zmq.DEALER)
client.connect(POBLANO)

jobs = ['GitHub', 'Jenkins', 'Review Board', 'Pivotal Tracker']
for j in jobs:
       client.send(j)

poller = zmq.Poller()
poller.register(client, zmq.POLLIN)

for _i in range(len(jobs)):
    poller.poll()
    msg = client.recv_multipart()
    print(' '.join(msg))

# Don't bother with any cleanup, everything gets destroyed at once anyway...