Suicidal Snail in Python

"""
Suicidal Snail

Author: Min RK <moc.liamg|krnimajneb#moc.liamg|krnimajneb>
"""

import sys
import threading
import time
import random

import zmq

from zhelpers import zpipe

# ---------------------------------------------------------------------
# This is our subscriber
# It connects to the publisher and subscribes to everything. It
# sleeps for a short time between messages to simulate doing too
# much work. If a message is more than 1 second late, it croaks.

MAX_ALLOWED_DELAY = 1.0 # secs

def subscriber(pipe):
# Subscribe to everything
ctx = zmq.Context.instance()
sub = ctx.socket(zmq.SUB)
sub.setsockopt(zmq.SUBSCRIBE, '')
sub.connect("tcp://localhost:5556")

# Get and process messages
while True:
clock = float(sub.recv())
# Suicide snail logic
if (time.time() - clock > MAX_ALLOWED_DELAY):
print >> sys.stderr, "E: subscriber cannot keep up, aborting\n",
break

# Work for 1 msec plus some random additional time
time.sleep(1e-3 * (1+2*random.random()))
pipe.send("gone and died")

# ---------------------------------------------------------------------
# This is our server task
# It publishes a time-stamped message to its pub socket every 1ms.

def publisher(pipe):
# Prepare publisher
ctx = zmq.Context.instance()
pub = ctx.socket(zmq.PUB)
pub.bind("tcp://*:5556")

while True:
# Send current clock (secs) to subscribers
pub.send(str(time.time()))
try:
signal = pipe.recv(zmq.DONTWAIT)
except zmq.ZMQError as e:
if e.errno == zmq.EAGAIN:
# nothing to recv
pass
else:
raise
else:
# received break message
break
time.sleep(1e-3) # 1msec wait

# This main thread simply starts a client, and a server, and then
# waits for the client to signal it's died.

def main():
ctx = zmq.Context.instance()
pub_pipe, pub_peer = zpipe(ctx)
sub_pipe, sub_peer = zpipe(ctx)

pub_thread = threading.Thread(target=publisher, args=(pub_peer,))
pub_thread.daemon=True
pub_thread.start()
sub_thread = threading.Thread(target=subscriber, args=(sub_peer,))
sub_thread.daemon=True
sub_thread.start()
# wait for sub to finish
sub_pipe.recv()
# tell pub to halt
pub_pipe.send("break")
time.sleep(0.1)

if __name__ == '__main__':
main()