doc/core/examples/threadedselect/blockingdemo.py

   1 # Copyright (c) Twisted Matrix Laboratories.
   2 # See LICENSE for details.
   3
   4
   5 from twisted.internet import _threadedselect
   6 _threadedselect.install()
   7
   8 from twisted.internet.defer import Deferred
   9 from twisted.python.failure import Failure
  10 from twisted.internet import reactor
  11 from twisted.python.runtime import seconds
  12 from itertools import count
  13 from Queue import Queue, Empty
  14
  15 class TwistedManager(object):
  16     def __init__(self):
  17         self.twistedQueue = Queue()
  18         self.key = count()
  19         self.results = {}
  20
  21     def getKey(self):
  22         # get a unique identifier
  23         return self.key.next()
  24
  25     def start(self):
  26         # start the reactor
  27         reactor.interleave(self.twistedQueue.put)
  28
  29     def _stopIterating(self, value, key):
  30         self.results[key] = value
  31
  32     def stop(self):
  33         # stop the reactor
  34         key = self.getKey()
  35         reactor.addSystemEventTrigger('after', 'shutdown',
  36             self._stopIterating, True, key)
  37         reactor.stop()
  38         self.iterate(key)
  39
  40     def getDeferred(self, d):
  41         # get the result of a deferred or raise if it failed
  42         key = self.getKey()
  43         d.addBoth(self._stopIterating, key)
  44         res = self.iterate(key)
  45         if isinstance(res, Failure):
  46             res.raiseException()
  47         return res
  48
  49     def poll(self, noLongerThan=1.0):
  50         # poll the reactor for up to noLongerThan seconds
  51         base = seconds()
  52         try:
  53             while (seconds() - base) <= noLongerThan:
  54                 callback = self.twistedQueue.get_nowait()
  55                 callback()
  56         except Empty:
  57             pass
  58
  59     def iterate(self, key=None):
  60         # iterate the reactor until it has the result we're looking for
  61         while key not in self.results:
  62             callback = self.twistedQueue.get()
  63             callback()
  64         return self.results.pop(key)
  65
  66 def fakeDeferred(msg):
  67     d = Deferred()
  68     def cb():
  69         print "deferred called back"
  70         d.callback(msg)
  71     reactor.callLater(2, cb)
  72     return d
  73
  74 def fakeCallback():
  75     print "twisted is still running"
  76
  77 def main():
  78     m = TwistedManager()
  79     print "starting"
  80     m.start()
  81     print "setting up a 1sec callback"
  82     reactor.callLater(1, fakeCallback)
  83     print "getting a deferred"
  84     res = m.getDeferred(fakeDeferred("got it!"))
  85     print "got the deferred:", res
  86     print "stopping"
  87     m.stop()
  88     print "stopped"
  89
  90
  91 if __name__ == '__main__':
  92     main()