Python开发之多个定时任务在单线程下执行的实例分析

单线程多定时任务

1、初始版本：

思路：定时器，说白了就是延时执行指定的程序，目前自己重构python里面的定时器不太现实，能力达不到，所以延时操作时还得用到系统定时器，不过我们可以改一下规则；把所有要进行定时操作的程序添加到特定列表中，把列表中定时时间最短程序拿出来，进行threading.Timer（time，callback）绑定，等时间超时触发自定义的callback，执行刚刚列表取出的程序；然后把时间更新，再次把列表中时间最短的程序拿出了，继续threading.Timer绑定，不断的迭代循环；当有新的定时任务加入到列表时，把当前的threading.Timer绑定取消，更新列表中的时间，再次取出最短时间，进行threading.Timer绑定......

代码：

import threading
import time

class Timer():
 '''单线程下的定时器'''

 def __init__(self):
 self.queues = []
 self.timer = None
 self.last_time = time.time()

 def start(self):
 item = self.get()
 if item:
 self.timer = threading.Timer(item[0],self.execute)
 self.timer.start()

 def add(self,item):
 print('add',item)
 self.flush_time()
 self.queues.append(item)
 self.queues.sort(key=lambda x:x[0])

 if self.timer:
 self.timer.cancel()
 self.timer = None
 self.start()

 def get(self):
 item = None
 if len(self.queues) > 0:
 item = self.queues[0]
 return item

 def pop(self):
 item = None
 if len(self.queues) > 0:
 item = self.queues.pop(0)
 return item

 def flush_time(self):
 curr_time = time.time()
 for i in self.queues:
 i[0] = i[0] - (curr_time - self.last_time)
 self.last_time = curr_time

 def execute(self):
 # if self.timer:
 # self.timer.cancel()
 # self.timer = None
 item = self.pop()
 self.flush_time()
 if item:
 callback = item[1]
 args = item[0]
 callback(args)
 self.start()

执行及输出：

if __name__ == '__main__': # 检测线程数
 def func(): while True: print(threading.active_count())
 time.sleep(1)
 
 f1 = threading.Thread(target=func)
 f1.start() 
 import logging
 logging.basicConfig(level=logging.INFO,format="%(asctime)s %(message)s", datefmt="%m/%d/%Y %H:%M:%S [%A]") def func1(*args):
 logging.info('func1 %s'%args) # time.sleep(5)
 
 def func2(*args):
 logging.info('func2 %s' % args) # time.sleep(5)
 def func3(*args):
 logging.info('func3 %s' % args) # time.sleep(5)
 
 def func4(*args):
 logging.info('func4 %s' % args) # time.sleep(5)
 
 def func5(*args):
 logging.info('func5 %s' % args) # time.sleep(5)
 
 
 # 测试
 t1 = Timer()
 logging.info('start')
 t1.add([5,func1])
 time.sleep(0.5)
 t1.add([4,func2])
 time.sleep(0.5)
 t1.add([3,func3])
 time.sleep(0.5)
 t1.add([2,func4])
 time.sleep(0.5)
 t1.add([1,func5])
 time.sleep(5)
 t1.add([1,func1])
 t1.add([2,func2])
 t1.add([3,func3])
 t1.add([4,func4])
 t1.add([5,func5]) 
 # 

输出 # 2 # 07/27/2017 10:36:47 [Thursday] start # add [5, <function func1 at 0x000000D79FC77E18>] # add [4, <function func2 at 0x000000D79FCA8488>] # 3 # add [3, <function func3 at 0x000000D79FCA8510>] # add [2, <function func4 at 0x000000D79FCA8598>] # 3 # add [1, <function func5 at 0x000000D79FCA8620>] # 3 # 07/27/2017 10:36:50 [Thursday] func5 1 # 07/27/2017 10:36:51 [Thursday] func4 0.498349666595459 # 3 # 07/27/2017 10:36:51 [Thursday] func3 0.49782633781433105 # 07/27/2017 10:36:52 [Thursday] func2 0.49848270416259766 # 3 # 07/27/2017 10:36:52 [Thursday] func1 0.48449039459228516 # 2 # 2 # add [1, <function func1 at 0x000000D79FC77E18>] # add [2, <function func2 at 0x000000D79FCA8488>] # add [3, <function func3 at 0x000000D79FCA8510>] # add [4, <function func4 at 0x000000D79FCA8598>] # add [5, <function func5 at 0x000000D79FCA8620>] # 3 # 07/27/2017 10:36:55 [Thursday] func1 0.9990766048431396 # 3 # 07/27/2017 10:36:56 [Thursday] func2 0.9988017082214355 # 3 # 07/27/2017 10:36:57 [Thursday] func3 0.99928879737854 # 07/27/2017 10:36:58 [Thursday] func4 0.9991350173950195 # 3 # 3 # 07/27/2017 10:36:59 [Thursday] func5 0.9988160133361816

执行代码

注：查看代码输出，所有的定时器都按照标定的时间依次执行，非常完美，一切看起来很美好，只是看起来，呵呵哒，当你把func里面的time.sleep(5)启用后，线程数蹭蹭的上来了;原因是上个定时器callback还是执行中，下个定时器已经启动了，这时就又新增了一个线程，哎,失败

2、修订版本

思路：利用生成者消费者模型,用到threading.Condition条件变量；强制永远启用的是一个Timer!

代码：

import time
import threading
import logging

class NewTimer(threading.Thread):
 '''单线程下的定时器'''
 def __init__(self):
 super().__init__()
 self.queues = []
 self.timer = None
 self.cond = threading.Condition()

 def run(self):
 while True:
 # print('NewTimer',self.queues)
 self.cond.acquire()
 item = self.get()
 callback = None
 if not item:
 logging.info('NewTimer wait')
 self.cond.wait()
 elif item[0] <= time.time():
 new_item = self.pop()
 callback = new_item[1]
 else:
 logging.info('NewTimer start sys timer and wait')
 self.timer = threading.Timer(item[0]-time.time(),self.execute)
 self.timer.start()
 self.cond.wait()
 self.cond.release()

 if callback:
 callback(item[0])

 def add(self, item):
 # print('add', item)
 self.cond.acquire()
 item[0] = item[0] + time.time()
 self.queues.append(item)
 self.queues.sort(key=lambda x: x[0])
 logging.info('NewTimer add notify')
 if self.timer:
 self.timer.cancel()
 self.timer = None
 self.cond.notify()
 self.cond.release()

 def pop(self):
 item = None
 if len(self.queues) > 0:
 item = self.queues.pop(0)
 return item

 def get(self):
 item = None
 if len(self.queues) > 0:
 item = self.queues[0]
 return item

 def execute(self):
 logging.info('NewTimer execute notify')
 self.cond.acquire()
 self.cond.notify()
 self.cond.release()

执行及输出：

if __name__ == '__main__': def func(): while True: print(threading.active_count())
 time.sleep(1)

 f1 = threading.Thread(target=func)
 f1.start()
 logging.basicConfig(level=logging.INFO,format="%(asctime)s %(message)s", datefmt="%m/%d/%Y %H:%M:%S [%A]")

 newtimer = NewTimer()
 newtimer.start() def func1(*args):
 logging.info('func1 %s'%args)
 time.sleep(5) def func2(*args):
 logging.info('func2 %s' % args)
 time.sleep(5) def func3(*args):
 logging.info('func3 %s' % args)
 time.sleep(5) def func4(*args):
 logging.info('func4 %s' % args)
 time.sleep(5) def func5(*args):
 logging.info('func5 %s' % args)
 time.sleep(5)

 newtimer.add([5,func1])
 newtimer.add([4,func2])
 newtimer.add([3,func3])
 newtimer.add([2,func4])
 newtimer.add([1,func5])
 time.sleep(1)
 newtimer.add([1,func1])
 newtimer.add([2,func2])
 newtimer.add([3,func3])
 newtimer.add([4,func4])
 newtimer.add([5,func5])# 

输出# 2# 07/27/2017 11:26:19 [Thursday] NewTimer wait# 07/27/2017 11:26:19 [Thursday] NewTimer add notify# 07/27/2017 11:26:19 [Thursday] NewTimer add notify# 07/27/2017 11:26:19 [Thursday] NewTimer add notify# 07/27/2017 11:26:19 [Thursday] NewTimer add notify# 07/27/2017 11:26:19 [Thursday] NewTimer add notify# 07/27/2017 11:26:19 [Thursday] NewTimer start sys timer and wait# 07/27/2017 11:26:20 [Thursday] NewTimer execute notify# 4# 07/27/2017 11:26:20 [Thursday] func5 1501125980.2175007# 07/27/2017 11:26:20 [Thursday] NewTimer add notify# 07/27/2017 11:26:20 [Thursday] NewTimer add notify# 07/27/2017 11:26:20 [Thursday] NewTimer add notify# 07/27/2017 11:26:20 [Thursday] NewTimer add notify# 07/27/2017 11:26:20 [Thursday] NewTimer add notify# 3# 3# 3# 3# 3# 07/27/2017 11:26:25 [Thursday] func4 1501125981.2175007# 3# 3# 3# 3# 07/27/2017 11:26:30 [Thursday] func1 1501125981.218279# 3# 3# 3# 3# 3# 3# 07/27/2017 11:26:35 [Thursday] func3 1501125982.2175007# 3# 3# 3# 3# 07/27/2017 11:26:40 [Thursday] func2 1501125982.218279# 3# 3# 3# 3# 3# 07/27/2017 11:26:45 [Thursday] func2 1501125983.2175007# 3# 3# 3# 3# 3# 07/27/2017 11:26:50 [Thursday] func3 1501125983.218279# 3# 3# 3# 3# 3# 07/27/2017 11:26:55 [Thursday] func1 1501125984.2175007# 3# 3# 3# 3# 3# 07/27/2017 11:27:00 [Thursday] func4 1501125984.218279# 3# 3# 3# 3# 3# 07/27/2017 11:27:05 [Thursday] func5 1501125985.218279# 3# 3# 3# 3# 3# 07/27/2017 11:27:10 [Thursday] NewTimer wait

输出

注：这次无论如何测试线程数也不会蹭蹭的上涨，同时可以实现多定时器任务要求；缺点：用到了两线程，没有用到单线程去实现，第二时间精准度问题，需要等待上个定时程序执行完毕，程序才能继续运行