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ZeroMQ N to N async pattern in Python

由 十年热恋 提交于 2019-12-06 15:37:02

Absolutely you should not comment proxy function. The problem is because zmq.proxy function block forever and you ran it with "run_until_complete" event loop. You should change event loop execution type to run_forever.

As always, the answer is in simplicity. By separating it into 3 scripts, we don't have to work with threads and asynchronous programming, so this should help more people.

Open 6 terminals and run the following commands in a terminal each:

  1. python proxy_topic.py # proxy / ROS topic
  2. python proxy_pub.py # publish "Hello World"
  3. python proxy_pub.py jp # publish "Hello Sekai"
  4. python proxy_sub.py # receive all messages
  5. python proxy_sub.py en # receive "Hello World" only; not necessary
  6. python proxy_sub.py jp # receive "Hello Sekai" only; not necessary

proxy_topic.py

import sys
import zmq
from zmq import Context


class ProxyPub:
    def __init__(self, address='127.0.0.1', port1='5566', port2='5567'):
        # get ZeroMQ version
        print("Current libzmq version is %s" % zmq.zmq_version())
        print("Current  pyzmq version is %s" % zmq.pyzmq_version())

        self.context = Context.instance()
        # 2 sockets, because we can only bind once to a socket (as opposed to connect)
        self.url1 = "tcp://{}:{}".format(address, port1)
        self.url2 = "tcp://{}:{}".format(address, port2)

        self.xpub_xsub_proxy()

    # N publishers to 1 sub; proxy 1 sub to 1 pub; publish to M subscribers
    def xpub_xsub_proxy(self):
        print("Init proxy")

        # Socket subscribing to publishers
        frontend_pubs = self.context.socket(zmq.XSUB)
        frontend_pubs.bind(self.url1)

        # Socket publishing to subscribers
        backend_subs = self.context.socket(zmq.XPUB)
        backend_subs.bind(self.url2)

        print("Try: Proxy... CONNECT!")
        zmq.proxy(frontend_pubs, backend_subs)
        print("CONNECT successful!")


if __name__ == '__main__':
    print("Arguments given: {}".format(sys.argv))
    ProxyPub()

proxy_pub.py

import sys
import zmq
from zmq import Context
import time


class ProxyPub:
    def __init__(self, lang='en', address='127.0.0.1', port='5566'):
        # get ZeroMQ version
        print("Current libzmq version is %s" % zmq.zmq_version())
        print("Current  pyzmq version is %s" % zmq.pyzmq_version())

        self.context = Context.instance()
        self.url = "tcp://{}:{}".format(address, port)

        self.pub_hello_world(lang)

    def pub_hello_world(self, lang):
        print("Init pub {}".format(lang))

        # connect, because many publishers - 1 subscriber
        pub = self.context.socket(zmq.PUB)
        pub.connect(self.url)

        if lang == 'en':
            message = "Hello World"
            sleep = 1
        else:
            message = "Hello Sekai"  # Japanese
            sleep = 2

        # wait proxy and subs to b ready
        time.sleep(.5)

        # keep publishing "Hello World" / "Hello Sekai" messages
        print("Pub {}: Going to pub messages!".format(lang))
        while True:
            # publish message to topic 'world'
            # multipart: topic, message; async always needs `send_multipart()`?
            pub.send_multipart([lang.encode('ascii'), message.encode('ascii')])
            print("Pub {}: Have send msg".format(lang))

            # slow down message publication
            time.sleep(sleep)


if __name__ == '__main__':
    print("Arguments given: {}".format(sys.argv))
    if len(sys.argv) == 1:
        ProxyPub()
    elif len(sys.argv) == 2:
        ProxyPub(lang=sys.argv[1])
    else:
        print("Too many arguments")

proxy_sub.py

import sys
import zmq
from zmq import Context
import time


class ProxyPub:
    def __init__(self, lang='', address='127.0.0.1', port='5567'):
        # get ZeroMQ version
        print("Current libzmq version is %s" % zmq.zmq_version())
        print("Current  pyzmq version is %s" % zmq.pyzmq_version())

        self.context = Context.instance()
        self.url = "tcp://{}:{}".format(address, port)

        self.sub_hello_world(lang)

    def sub_hello_world(self, lang):
        print("Init sub {}".format(lang))

        # connect, because many subscribers - 1 (proxy) pub
        sub = self.context.socket(zmq.SUB)
        sub.connect(self.url)
        # subscribe to topic 'en' or 'jp'
        sub.setsockopt(zmq.SUBSCRIBE, lang.encode('ascii'))

        # wait proxy to be ready; necessary?
        time.sleep(.2)

        # keep listening to all published message, filtered on topic
        print("Sub {}: Going to wait for messages!".format(lang))
        while True:
            msg_received = sub.recv_multipart()
            print("sub {}: {}".format(lang, msg_received))


if __name__ == '__main__':
    print("Arguments given: {}".format(sys.argv))
    if len(sys.argv) == 1:
        ProxyPub()
    elif len(sys.argv) == 2:
        ProxyPub(lang=sys.argv[1])
    else:
        print("Too many arguments")
标签
python
python-3.x
zeromq
python-asyncio
pyzmq
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