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#!/usr/bin/env python
# -*- coding: utf-8 -*-
from sys import stdout
import random
import string
import txnats
from twisted.logger import globalLogPublisher
from simple_log_observer import simpleObserver
from twisted.logger import Logger
log = Logger()
from twisted.internet import reactor
from twisted.internet.task import LoopingCall
from twisted.internet.endpoints import TCP4ClientEndpoint
from twisted.internet.endpoints import connectProtocol
responder_id = ''.join(
random.choice(string.ascii_uppercase + string.digits) for _ in range(8))
def respond_on_msg(nats_protocol, sid, subject, reply_to, payload):
"""
Write the message payload to standard out, and if
there is a reply_to, publish a message to it.
"""
stdout.write(payload.decode())
stdout.write("\r\n")
if reply_to:
nats_protocol.pub(reply_to, "Roger, from {}!".format(responder_id))
def listen(nats_protocol):
"""
When the protocol is first connected, make a subscription.
"""
log.info("HELLO LISTEN")
nats_protocol.sub("a-queue", "1",
queue_group="excelsior",
on_msg=respond_on_msg)
pinger = LoopingCall(nats_protocol.ping)
pinger.reactor = nats_protocol.reactor
pinger.start(10, now=True)
def create_client(reactor, host, port):
"""
Start a Nats Protocol and connect it to a NATS endpoint over TCP4
which subscribes a subject with a callback that sends a response
if it gets a reply_to.
"""
log.info("Start client.")
point = TCP4ClientEndpoint(reactor, host, port)
nats_protocol = txnats.io.NatsProtocol(verbose=False, on_connect=listen)
# Because NatsProtocol implements the Protocol interface, Twisted's
# connectProtocol knows how to connected to the endpoint.
connecting = connectProtocol(point, nats_protocol)
# Log if there is an error making the connection.
connecting.addErrback(on_fail_to_connect, nats_protocol)
# Log what is returned by the connectProtocol.
connecting.addCallback(lambda np: log.info("{p}", p=np))
return connecting
def on_fail_to_connect(error, nats_protocol):
"""Exit on failure, the process manager
should try restarting, (systemd)"""
log.error("{error}", error=error)
nats_protocol.reactor.stop()
def main(reactor):
host = "demo.nats.io"
port = 4222
create_client(reactor, host, port)
if __name__ == '__main__':
globalLogPublisher.addObserver(simpleObserver)
main(reactor)
reactor.run()
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