Python开发【笔记】：单线程下执行多个定时任务

单线程多定时任务

　　前言：公司业务需求，实例当中大量需要启动定时器的操作；大家都知道python中的定时器用的是threading.Timer，每当启动一个定时器时，程序内部起了一个线程，定时器触发执行结束后，线程自动销毁；这里就涉及到一个问题，如果同时有大量启动定时器的需求时，内部线程过多，程序肯定就崩了，有没有启一个线程就能完成定时器的操作呢？网上查了一些资料，还没有看到能解决目前问题的现成代码，不如自己搞一个试试

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
    #
    # 07/27/2017 10:36:47 [Thursday] start
    # add [5, <function func1 at 0x000000D79FC77E18>]
    # add [4, <function func2 at 0x000000D79FCA8488>]
    #
    # add [3, <function func3 at 0x000000D79FCA8510>]
    # add [2, <function func4 at 0x000000D79FCA8598>]
    #
    # add [1, <function func5 at 0x000000D79FCA8620>]
    #
    # 07/27/2017 10:36:50 [Thursday] func5 1
    # 07/27/2017 10:36:51 [Thursday] func4 0.498349666595459
    #
    # 07/27/2017 10:36:51 [Thursday] func3 0.49782633781433105
    # 07/27/2017 10:36:52 [Thursday] func2 0.49848270416259766
    #
    # 07/27/2017 10:36:52 [Thursday] func1 0.48449039459228516
    #
    #
    # 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>]
    #
    # 07/27/2017 10:36:55 [Thursday] func1 0.9990766048431396
    #
    # 07/27/2017 10:36:56 [Thursday] func2 0.9988017082214355
    #
    # 07/27/2017 10:36:57 [Thursday] func3 0.99928879737854
    # 07/27/2017 10:36:58 [Thursday] func4 0.9991350173950195
    #
    #
    # 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
#
# 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
#
# 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
#
#
#
#
#
# 07/27/2017 11:26:25 [Thursday] func4 1501125981.2175007
#
#
#
#
# 07/27/2017 11:26:30 [Thursday] func1 1501125981.218279
#
#
#
#
#
#
# 07/27/2017 11:26:35 [Thursday] func3 1501125982.2175007
#
#
#
#
# 07/27/2017 11:26:40 [Thursday] func2 1501125982.218279
#
#
#
#
#
# 07/27/2017 11:26:45 [Thursday] func2 1501125983.2175007
#
#
#
#
#
# 07/27/2017 11:26:50 [Thursday] func3 1501125983.218279
#
#
#
#
#
# 07/27/2017 11:26:55 [Thursday] func1 1501125984.2175007
#
#
#
#
#
# 07/27/2017 11:27:00 [Thursday] func4 1501125984.218279
#
#
#
#
#
# 07/27/2017 11:27:05 [Thursday] func5 1501125985.218279
#
#
#
#
#
# 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