Extend existing Twisted Service with another Socket/TCP/RPC Service to get Service informations
I'm implementing a Twisted-based Heartbeat Client/Server combo, based on this example. It is my first Twisted project.
Basically it consists of a UDP Listener (Receiver
), who calls a listener method (DetectorService.update
) on receiving packages. The DetectorService always holds a list of currently active/inactive clients (I extended the example a lot, but the core is still the same), making it possible to react on clients which seem disconnected for a specified timeout.
This is the source taken from the site:
UDP_PORT = 43278; CHECK_PERIOD = 20; CHECK_TIMEOUT = 15
import time
from twisted.application import internet, service
from twisted.internet import protocol
from twisted.python import log
class Receiver(protocol.DatagramProtocol):
"""Receive UDP packets and log them in the clients dictionary"""
def datagramReceived(self, data, (ip, port)):
if data == 'PyHB':
self.callback(ip)
class DetectorService(internet.TimerService):
"""Detect clients not sending heartbeats for too long"""
def __init__(self):
internet.TimerService.__init__(self, CHECK_PERIOD, self.detect)
self.beats = {}
def update(self, ip):
self.beats[ip] = time.time()
开发者_如何学编程 def detect(self):
"""Log a list of clients with heartbeat older than CHECK_TIMEOUT"""
limit = time.time() - CHECK_TIMEOUT
silent = [ip for (ip, ipTime) in self.beats.items() if ipTime < limit]
log.msg('Silent clients: %s' % silent)
application = service.Application('Heartbeat')
# define and link the silent clients' detector service
detectorSvc = DetectorService()
detectorSvc.setServiceParent(application)
# create an instance of the Receiver protocol, and give it the callback
receiver = Receiver()
receiver.callback = detectorSvc.update
# define and link the UDP server service, passing the receiver in
udpServer = internet.UDPServer(UDP_PORT, receiver)
udpServer.setServiceParent(application)
# each service is started automatically by Twisted at launch time
log.msg('Asynchronous heartbeat server listening on port %d\n'
'press Ctrl-C to stop\n' % UDP_PORT)
This heartbeat server runs as a daemon in background.
Now my Problem:
I need to be able to run a script "externally" to print the number of offline/online clients on the console, which the Receiver gathers during his lifetime (self.beats
). Like this:
$ pyhb showactiveclients
3 clients online
$ pyhb showofflineclients
1 client offline
So I need to add some kind of additional server (Socket, Tcp, RPC - it doesn't matter. the main point is that i'm able to build a client-script with the above behavior) to my DetectorService, which allows to connect to it from outside. It should just give a response to a request.
This server needs to have access to the internal variables of the running detectorservice instance, so my guess is that I have to extend the DetectorService with some kind of additionalservice.
After some hours of trying to combine the detectorservice with several other services, I still don't have an idea what's the best way to realize that behavior. So I hope that somebody can give me at least the essential hint how to start to solve this problem. Thanks in advance!!!
I think you already have the general idea of the solution here, since you already applied it to an interaction between Receiver
and DetectorService
. The idea is for your objects to have references to other objects which let them do what they need to do.
So, consider a web service that responds to requests with a result based on the beats
data:
from twisted.web.resource import Resource
class BeatsResource(Resource):
# It has no children, let it respond to the / URL for brevity.
isLeaf = True
def __init__(self, detector):
Resource.__init__(self)
# This is the idea - BeatsResource has a reference to the detector,
# which has the data needed to compute responses.
self._detector = detector
def render_GET(self, request):
limit = time.time() - CHECK_TIMEOUT
# Here, use that data.
beats = self._detector.beats
silent = [ip for (ip, ipTime) in beats.items() if ipTime < limit]
request.setHeader('content-type', 'text/plain')
return "%d silent clients" % (len(silent),)
# Integrate this into the existing application
application = service.Application('Heartbeat')
detectorSvc = DetectorService()
detectorSvc.setServiceParent(application)
.
.
.
from twisted.web.server import Site
from twisted.application.internet import TCPServer
# The other half of the idea - make sure to give the resource that reference
# it needs.
root = BeatsResource(detectorSvc)
TCPServer(8080, Site(root)).setServiceParent(application)
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