Exemples de code pour écrire des programmes non bloquants à l'aide du framework Twisted de Python

# ~*~ Twisted - A Python tale ~*~
 
from time import sleep
 
# Hello, I'm a developer and I mainly setup Wordpress.
def install_wordpress(customer):
  # Our hosting company Threads Ltd. is bad. I start installation and...
  print "Start installation for", customer
  # ...then wait till the installation finishes successfully. It is
  # boring and I'm spending most of my time waiting while consuming
  # resources (memory and some CPU cycles). It's because the process
  # is *blocking*.
  sleep(3)
  print "All done for", customer
 
# I do this all day long for our customers
def developer_day(customers):
  for customer in customers:
    install_wordpress(customer)
 
developer_day(["Bill", "Elon", "Steve", "Mark"])

   
$ ./deferreds.py 1

------ Running example 1 ------
Start installation for Bill
All done for Bill
Start installation
...
* Elapsed time: 12.03 seconds

import threading
 
# The company grew. We now have many customers and I can't handle the
# workload. We are now 5 developers doing exactly the same thing.
def developers_day(customers):
  # But we now have to synchronize... a.k.a. bureaucracy
  lock = threading.Lock()
  #
  def dev_day(id):
    print "Goodmorning from developer", id
    # Yuck - I hate locks...
    lock.acquire()
    while customers:
      customer = customers.pop(0)
      lock.release()
      # My Python is less readable
      install_wordpress(customer)
      lock.acquire()
    lock.release()
    print "Bye from developer", id
  # We go to work in the morning
  devs = [threading.Thread(target=dev_day, args=(i,)) for i in range(5)]
  [dev.start() for dev in devs]
  # We leave for the evening
  [dev.join() for dev in devs]
 
# We now get more done in the same time but our dev process got more
# complex. As we grew we spend more time managing queues than doing dev
# work. We even had occasional deadlocks when processes got extremely
# complex. The fact is that we are still mostly pressing buttons and
# waiting but now we also spend some time in meetings.
developers_day(["Customer %d" % i for i in xrange(15)])

 $ ./deferreds.py 2

------ Running example 2 ------
Goodmorning from developer 0Goodmorning from developer
1Start installation forGoodmorning from developer 2
Goodmorning from developer 3Customer 0
...
from developerCustomer 13 3Bye from developer 2
* Elapsed time: 9.02 seconds

# For years we thought this was all there was... We kept hiring more
# developers, more managers and buying servers. We were trying harder
# optimising processes and fire-fighting while getting mediocre
# performance in return. Till luckily one day our hosting
# company decided to increase their fees and we decided to
# switch to Twisted Ltd.!
 
from twisted.internet import reactor
from twisted.internet import defer
from twisted.internet import task
 
# Twisted has a slightly different approach
def schedule_install(customer):
  # They are calling us back when a Wordpress installation completes.
  # They connected the caller recognition system with our CRM and
  # we know exactly what a call is about and what has to be done next.
  #
  # We now design processes of what has to happen on certain events.
  def schedule_install_wordpress():
      def on_done():
        print "Callback: Finished installation for", customer
    print "Scheduling: Installation for", customer
    return task.deferLater(reactor, 3, on_done)
  #
  def all_done(_):
    print "All done for", customer
  #
  # For each customer, we schedule these processes on the CRM
  # and that
  # is all our chief-Twisted developer has to do
  d = schedule_install_wordpress()
  d.addCallback(all_done)
  #
  return d
 
# Yes, we don't need many developers anymore or any synchronization.
# ~~ Super-powered Twisted developer ~~
def twisted_developer_day(customers):
  print "Goodmorning from Twisted developer"
  #
  # Here's what has to be done today
  work = [schedule_install(customer) for customer in customers]
  # Turn off the lights when done
  join = defer.DeferredList(work)
  join.addCallback(lambda _: reactor.stop())
  #
  print "Bye from Twisted developer!"
# Even his day is particularly short!
twisted_developer_day(["Customer %d" % i for i in xrange(15)])
 
# Reactor, our secretary uses the CRM and follows-up on events!
reactor.run()

------ Running example 3 ------
Goodmorning from Twisted developer
Scheduling: Installation for Customer 0
....
Scheduling: Installation for Customer 14
Bye from Twisted developer!
Callback: Finished installation for Customer 0
All done for Customer 0
Callback: Finished installation for Customer 1
All done for Customer 1
...
All done for Customer 14
* Elapsed time: 3.18 seconds

# Twisted gave us utilities that make our code way more readable!
@defer.inlineCallbacks
def inline_install(customer):
  print "Scheduling: Installation for", customer
  yield task.deferLater(reactor, 3, lambda: None)
  print "Callback: Finished installation for", customer
  print "All done for", customer
 
def twisted_developer_day(customers):
  ... same as previously but using inline_install() instead of schedule_install()
 
twisted_developer_day(["Customer %d" % i for i in xrange(15)])
reactor.run()

@defer.inlineCallbacks
def inline_install(customer):
  ... same as above
 
# The new "problem" is that we have to manage all this concurrency to
# avoid causing problems to others, but this is a nice problem to have.
def twisted_developer_day(customers):
  print "Goodmorning from Twisted developer"
  work = (inline_install(customer) for customer in customers)
  #
  # We use the Cooperator mechanism to make the secretary not
  # service more than 5 customers simultaneously.
  coop = task.Cooperator()
  join = defer.DeferredList([coop.coiterate(work) for i in xrange(5)])
  #
  join.addCallback(lambda _: reactor.stop())
  print "Bye from Twisted developer!"
 
twisted_developer_day(["Customer %d" % i for i in xrange(15)])
reactor.run()
 
# We are now more lean than ever, our customers happy, our hosting
# bills ridiculously low and our performance stellar.
# ~*~ THE END ~*~

$ ./deferreds.py 5
------ Running example 5 ------
Goodmorning from Twisted developer
Bye from Twisted developer!
Scheduling: Installation for Customer 0
...
Callback: Finished installation for Customer 4
All done for Customer 4
Scheduling: Installation for Customer 5
...
Callback: Finished installation for Customer 14
All done for Customer 14
* Elapsed time: 9.19 seconds

..
 
# 代码片段
 
  def dataReceived(self, data):
    now = int(time.time())
 
    for ftype, data in self.fpcodec.feed(data):
      if ftype == 'oob':
        self.msg('OOB:', repr(data))
      elif ftype == 0x81: # 对服务器请求的心跳应答(这个是解析 防疲劳驾驶仪,发给gps上位机的,然后上位机发给服务器的)
        self.msg('FP.PONG:', repr(data))
      else:
        self.msg('TODO:', (ftype, data))
      d = deferToThread(self.redis.zadd, "beier:fpstat:fps", now, self.devid)
      d.addCallback(self._doResult, extra)

# -*- coding: utf-8 -*-
 
from twisted.internet import defer, reactor
from twisted.internet.threads import deferToThread
 
import functools
import time
 
# 耗时操作 这是一个同步阻塞函数
def mySleep(timeout):
  time.sleep(timeout)
 
  # 返回值相当于加进了callback里
  return 3
 
def say(result):
  print "耗时操作结束了, 并把它返回的结果给我了", result
 
# 用functools.partial包装一下, 传递参数进去
cb = functools.partial(mySleep, 3)
d = deferToThread(cb)
d.addCallback(say)
 
print "你还没有结束我就执行了, 哈哈"
 
reactor.run()