Bug in pyzmq

bug-description.markdown

This bug is really bizarre: I'm doing some operations inside a class and received a "core dumped" (the process is killed) when trying to destroy the context. But when I do the same operations outside the class, the error simply does not happen!

I can reproduce the bug with two scripts:

• server.py: creates a context, creates and binds to one zmq.REP socket and start a main loop in which it receives and answers requests (using recv_json and send_json). When receives SIGINT (KeyboardInterrupt), destroy the context and exit.
• client.py: creates a context, starts a process to run server.py (using subprocess.Popen), connects to server's socket, send/recv a JSON, destroys its context and finishes server's process sending a SIGINT.

I've implemented another version of client.py without using a class (client_without_class.py) but doing the same things and the error simply does not happen! The output for the two implementations is shown below:

$ python client_without_class.py 
Creating client
Sending/receiving JSON
Destroying client's context
Finishing server's process

$ python client.py 
Creating client
Sending/receiving JSON
Destroying client's context
File exists (epoll.cpp:69)
Aborted (core dumped)

System information:

• zmq.__version__ = '2.1.11'
• Python version = 2.7.3
• OS = Ubuntu 12.04 LTS

client.py

#!/usr/bin/env python
# coding: utf-8

from signal import SIGINT, SIGKILL
from time import sleep
from subprocess import Popen, PIPE
import shlex
import zmq


time_to_sleep = 0.15

class Client():
    def __init__(self):
        self.context = zmq.Context()
        self.start_server_process()

    def start_server_process(self):
        self.server = Popen(shlex.split('python server.py'),
                             stdin=PIPE, stdout=PIPE, stderr=PIPE)
        for line in self.server.stdout.readline():
            if 'main loop' in line:
                break

    def end_server_process(self):
        self.server.send_signal(SIGINT)
        sleep(time_to_sleep)
        self.server.send_signal(SIGKILL)
        self.server.wait()

    def send_and_receive_json(self):
        api = self.context.socket(zmq.REQ)
        api.connect('tcp://localhost:5555')
        cmd = {'command': 'add job', 'worker': 'test', 'document': 'eggs'}
        api.send_json(cmd)
        sleep(time_to_sleep)
        try:
            message = api.recv_json(zmq.NOBLOCK)
        except zmq.ZMQError:
            pass

print 'Creating client'
client = Client()
print 'Sending/receiving JSON'
client.send_and_receive_json()
print "Destroying client's context"
client.context.destroy()
print "Finishing server's process"
client.end_server_process()

client_without_class.py

#!/usr/bin/env python
# coding: utf-8

from signal import SIGINT, SIGKILL
from time import sleep
from subprocess import Popen, PIPE
import shlex
import zmq


time_to_sleep = 0.15

print 'Creating client'
context = zmq.Context()
server = Popen(shlex.split('python server.py'),
               stdin=PIPE, stdout=PIPE, stderr=PIPE)
for line in server.stdout.readline():
    if 'main loop' in line:
        break

print 'Sending/receiving JSON'
api = context.socket(zmq.REQ)
api.connect('tcp://localhost:5555')
cmd = {'command': 'add job', 'worker': 'test', 'document': 'eggs'}
api.send_json(cmd)
sleep(time_to_sleep)
try:
    message = api.recv_json(zmq.NOBLOCK)
except zmq.ZMQError:
    pass

print "Destroying client's context"
context.destroy()

print "Finishing server's process"
server.send_signal(SIGINT)
sleep(time_to_sleep)
server.send_signal(SIGKILL)
server.wait()

server.py

#!/usr/bin/env python
# coding: utf-8

from sys import stdout
from time import sleep
import zmq


def say(text):
    stdout.write(text)
    stdout.write('\n')
    stdout.flush()

context = zmq.Context()
socket = context.socket(zmq.REP)
socket.bind('tcp://*:5555')
say('[server] Started - running main loop')

try:
    while True:
        message = socket.recv_json()
        say('[server] Received JSON: {}'.format(message))
        socket.send_json({'answer': 'hello'})
except KeyboardInterrupt:
    context.destroy()

test.sh

#!/bin/bash

export WORKON_HOME="$HOME/.virtualenvs"
source /usr/local/bin/virtualenvwrapper.sh

mkvirtualenv --no-site-packages pyzmq-test
cdvirtualenv
pip install cython

git clone https://github.com/minrk/pyzmq.git
cd pyzmq/
git checkout i211
python setup.py configure --zmq=/usr/lib/
python setup.py build_ext --inplace
python setupegg.py develop

cd ..
git clone git://gist.github.com/2862393.git zeromq-bug
cd zeromq-bug
echo '*** Running client without class'
python client_without_class.py
echo '*** Running client with class'
python client.py