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python zerorpc and multiprocessing issue

I'm implementing a bi-directional ping-pong demo app between an electron app and a python backend.
This is the code for the python part which causes the problems:
import sys
import zerorpc
import time
from multiprocessing import Process
def ping_response():
print("Sleeping")
time.sleep(5)
c = zerorpc.Client()
c.connect("tcp://127.0.0.1:4243")
print("sending pong")
c.pong()
class Api(object):
def echo(self, text):
"""echo any text"""
return text
def ping(self):
p = Process(target=ping_response, args=())
p.start()
print("got ping")
return
def parse_port():
port = 4242
try:
port = int(sys.argv[1])
except Exception as e:
pass
return '{}'.format(port)
def main():
addr = 'tcp://127.0.0.1:' + parse_port()
s = zerorpc.Server(Api())
s.bind(addr)
print('start running on {}'.format(addr))
s.run()
if __name__ == '__main__':
main()
Each time ping() is called from javascript side it will start a new process that simulates some work (sleeping for 5 seconds) and replies by calling pong on nodejs server to indicate work is done.
The issue is that the pong() request never gets to javascript side. If instead of spawning a new process I create a new thread using _thread and execute the same code in ping_response(), the pong request arrives in the javascript side. Also if I manually run the bash command zerorpc tcp://localhost:4243 pong I can see that the pong request is received by the nodejs script so the server on the javascript side works ok.
What happens with zerorpc client when I create a new process and it doesn't manage to send the request ?
Thank you.
EDIT
It seems it gets stuck in c.pong()

Try using gipc.start_process() from the gipc module (via pip) instead of multiprocessing.Process(). It creates a new gevent context which otherwise multiprocessing will accidentally inherit.

How to stop a websocket client without stopping reactor

I have an app similar to a chat-room writing in python that intends to do the following things:
A prompt for user to input websocket server address.
Then create a websocket client that connects to server and send/receive messages. Disable the ability to create a websocket client.
After receiving "close" from server (NOT a close frame), client should drop connecting and re-enable the app to create a client. Go back to 1.
If user exits the app, it exit the websocket client if there is one running.
My approach for this is using a main thread to deal with user input. When user hits enter, a thread is created for WebSocketClient using AutoBahn's twisted module and pass a Queue to it. Check if the reactor is running or not and start it if it's not.
Overwrite on message method to put a closing flag into the Queue when getting "close". The main thread will be busy checking the Queue until receiving the flag and go back to start. The code looks like following.
Main thread.
def main_thread():
while True:
text = raw_input("Input server url or exit")
if text == "exit":
if myreactor:
myreactor.stop()
break
msgq = Queue.Queue()
threading.Thread(target=wsthread, args=(text, msgq)).start()
is_close = False
while True:
if msgq.empty() is False:
msg = msgq.get()
if msg == "close":
is_close = True
else:
print msg
if is_close:
break
print 'Websocket client closed!'
Factory and Protocol.
class MyProtocol(WebSocketClientProtocol):
def onMessage(self, payload, isBinary):
msg = payload.decode('utf-8')
self.Factory.q.put(msg)
if msg == 'close':
self.dropConnection(abort=True)
class WebSocketClientFactoryWithQ(WebSocketClientFactory):
def __init__(self, *args, **kwargs):
self.queue = kwargs.pop('queue', None)
WebSocketClientFactory.__init__(self, *args, **kwargs)
Client thread.
def wsthread(url, q):
factory = WebSocketClientFactoryWithQ(url=url, queue=q)
factory.protocol = MyProtocol
connectWS(Factory)
if myreactor is None:
myreactor = reactor
reactor.run()
print 'Done'
Now I got a problem. It seems that my client thread never stops. Even if I receive "close", it seems still running and every time I try to recreate a new client, it creates a new thread. I understand the first thread won't stop since reactor.run() will run forever, but from the 2nd thread and on, it should be non-blocking since I'm not starting it anymore. How can I change that?
EDIT:
I end up solving it with
Adding stopFactory() after disconnect.
Make protocol functions with reactor.callFromThread().
Start the reactor in the first thread and put clients in other threads and use reactor.callInThread() to create them.

Your main_thread creates new threads running wsthread. wsthread uses Twisted APIs. The first wsthread becomes the reactor thread. All subsequent threads are different and it is undefined what happens if you use a Twisted API from them.
You should almost certainly remove the use of threads from your application. For dealing with console input in a Twisted-based application, take a look at twisted.conch.stdio (not the best documented part of Twisted, alas, but just what you want).

How to run python-daemon with twisted

I am trying to run a daemon process using python-daemon library. I am also using twisted for networking.
The server is pretty simple:
class Echoer(pb.Root):
def remote_echo(self, st):
print 'echoing:', st
return st
if __name__ == '__main__':
serverfactory = pb.PBServerFactory(Echoer())
reactor.listenTCP(8789, serverfactory)
reactor.run()
And the client which is also supposed to be the daemon process follows as:
class App():
def __init__(self):
self.stdin_path = '/dev/null'
self.stdout_path = '/dev/tty'
self.stderr_path = '/dev/null'
self.pidfile_path = '/tmp/foo.pid'
self.pidfile_timeout = 5
def run(self):
clientfactory = pb.PBClientFactory()
reactor.connectTCP("localhost", 8789, clientfactory)
d = clientfactory.getRootObject()
d.addCallback(self.send_msg)
reactor.run()
def send_msg(self, result):
d = result.callRemote("echo", "hello network")
d.addCallback(self.get_msg)
def get_msg(self, result):
print "server echoed: ", result
app = App()
daemon_runner = runner.DaemonRunner(app)
daemon_runner.do_action()
When I run the client as python test.py start the daemon process is started but somehow the connection is not established.
But if I changed the last lines in the client as below:
app = App()
app.run()
Then the connection would be correctly established and working. But in this case it is not a daemon process anymore.
What am I missing here? How can I achieve it?

Twisted has daemonizing capabilities built-in already, so you don't need to add python-daemon. There may be some funny behavior overlaps between the two that may be biting you. As you've seen, once you've gotten your application it's pretty easy to run in the foreground as you've done above. It's also pretty easy to run it as a daemon; see the twistd description and twistd man page for more info on twistd, but basically you're just going to add a few lines of boilerplate and run your server through twistd.
See the article Running a Twisted Perspective Broker example with twistd for a step-by-step walkthrough of how to do it.

How to gracefully exit application started with twistd?

I have a jabber client that is reading from its stdin and posting PubSub messages. If I get EOF on stdin, I want to terminate the client.
I first tried sys.exit(), but this causes an exception and the client does not exit. I then did some searching and found out that I should call reactor.stop(), but I am unable to make this work. The following code in my client:
from twisted.internet import reactor
reactor.stop()
Results in exceptions.AttributeError: 'module' object has no attribute 'stop'
What do I need to do to cause twistd to shut my application down and exit?
EDIT 2
The original problem was caused by some symlinks messing up the module import. After fixing that problem, I get a new exception:
twisted.internet.error.ReactorNotRunning: Can't stop reactor that isn't running.
After the exception, twistd shuts down. I think this may be caused by the call to MyClient.loop in MyClient.connectionInitialized. Perhaps I need to defer the call until later?
EDIT
Here's the .tac file for my client
import sys
from twisted.application import service
from twisted.words.protocols.jabber.jid import JID
from myApp.clients import MyClient
clientJID = JID('client#example.com')
serverJID = JID('pubsub.example.com')
password = 'secret'
application = service.Application('XMPP client')
xmppClient = client.XMPPClient(clientJID, password)
xmppClient.logTraffic = True
xmppClient.setServiceParent(application)
handler = MyClient(clientJID, serverJID, sys.stdin)
handler.setHandlerParent(xmppClient)
Which I'm invoking with
twistd -noy sentry/myclient.tac < input.txt
Here's the code for MyClient:
import os
import sys
import time
from datetime import datetime
from wokkel.pubsub import PubSubClient
class MyClient(PubSubClient):
def __init__(self, entity, server, file, sender=None):
self.entity = entity
self.server = server
self.sender = sender
self.file = file
def loop(self):
while True:
line = self.file.readline()
if line:
print line
else:
from twisted.internet import reactor
reactor.stop()
def connectionInitialized(self):
self.loop()

from twisted.internet import reactor
reactor.stop()
that should work. The fact that it doesn't means something else is wrong on your application. I can't figure out what's wrong from the information you provided.
Can you provide more (all) of the code?
EDIT:
Ok, now the problem is that you don't stop your own while True loop, so it will keep looping and eventually stop the reactor again.
Try this:
from twisted.internet import reactor
reactor.stop()
return
Now, I suspect your loop isn't very good thing for a event-driven framework. While you're just printing lines, it is fine, but depending on what you want to really do (I suspect you'll do more than just print lines) you'll have to refactor that loop to work with events.

Use reactor.callFromThread(reactor.stop) instead of reactor.stop. This should solve the issue.

I used to do this way (in sigint handler of a non-twistd called application):
reactor.removeAll()
reactor.iterate()
reactor.stop()
I'm not 100% sure it is the right way, but twisted is happy
the same application started in a tac is handled directly by twistd signal handler, I've found this question because I have some rpc client requests that I would to wait for and handle result before exiting and looks like twistd is just killing the reactor without letting the call finish

Python Web Server - Getting it to do other tasks

Using the following example I can get a basic web server running but my problem is that the handle_request() blocks the do_something_else() until a request comes in. Is there any way around this to have the web server do other back ground tasks?
def run_while_true(server_class=BaseHTTPServer.HTTPServer,
handler_class=BaseHTTPServer.BaseHTTPRequestHandler):
server_address = ('', 8000)
httpd = server_class(server_address, handler_class)
while keep_running():
httpd.handle_request()
do_something_else()

You can use multiple threads of execution through the Python threading module. An example is below:
import threading
# ... your code here...
def run_while_true(server_class=BaseHTTPServer.HTTPServer,
handler_class=BaseHTTPServer.BaseHTTPRequestHandler):
server_address = ('', 8000)
httpd = server_class(server_address, handler_class)
while keep_running():
httpd.handle_request()
if __name__ == '__main__':
background_thread = threading.Thread(target=do_something_else)
background_thread.start()
# ... web server start code here...
background_thread.join()
This will cause a thread which executes do_something_else() to start before your web server. When the server shuts down, the join() call ensures do_something_else finishes before the program exits.

You should have a thread that handles http requests, and a thread that does do_something_else().