twisted reactor calllater实现

1.      calllater实现代码

测试源码：

from twisted.internet import reactor
from twisted.internet import defer

def func_1():
    print('calllater测试')
    time.sleep(5)
    print('calllater结束')

# error handle
def test_deferred_a():

    #d = test_retrurn_deferred()

    reactor.callLater(4, func_1)

    reactor.callLater(15, reactor.stop)

    reactor.run()

if __name__ == '__main__':

    test_deferred_a()

1.1.    第一步：调用calllater

reactor.callLater(3, d.callback, 8)

先找到calllater

# <twisted.internet.selectreactor.SelectReactor object at 0x000000CE3BFC72B0>
@implementer(IReactorCore, IReactorTime,
IReactorPluggableResolver,
            
IReactorPluggableNameResolver, _ISupportsExitSignalCapturing)
class ReactorBase(object):
    """
    Default base class for Reactors.
    """
    def callLater(self,
_seconds, _f, *args, **kw):
        """See
twisted.internet.interfaces.IReactorTime.callLater.
        """
        assert callable(_f), "%s
is not callable" % _f
        assert _seconds
>= 0, \
               "%s
is not greater than or equal to 0 seconds" % (_seconds,)
        tple = DelayedCall(self.seconds()
+ _seconds, _f, args, kw,
                           self._cancelCallLater,
                           self._moveCallLaterSooner,
                           seconds=self.seconds)
        self._newTimedCalls.append(tple)
        return tple

DelayedCall基本上可以把它当作一个中间类，用于保存一些信息。

结果就是向self._newTimedCalls添加一个定时调用

self._newTimedCalls.append(tple)

可以看一下它的具体内容

_newTimedCalls= <class 'list'>:
[<twisted.internet.base.DelayedCall object at 0x000000CE3C2EA668>]

1.2.   
第二步

reactor.run()

跳过一些前置处理内容，直接到mainloop

def mainLoop(self):
    while self._started:
        try:
            while self._started:
                # Advance
simulation time in delayed event
                # processors.
                self.runUntilCurrent()
                t2 = self.timeout()
                t = self.running and t2
                self.doIteration(t)
        except:
            log.msg("Unexpected
error in main loop.")
            log.err()
        else:
            log.msg('Main loop
terminated.')

进入self.runUntilCurrent()

def runUntilCurrent(self):
    """

        运行所有挂起的calls
    Run all pending timed calls.
    """
    if self.threadCallQueue:
        # Keep track of how
many calls we actually make, as we're
        # making them, in case another
call is added to the queue
        # while we're in this loop.
        count = 0
        total = len(self.threadCallQueue)
        for (f, a,
kw) in self.threadCallQueue:
            try:
                f(*a, **kw)
            except:
                log.err()
            count += 1
            if count ==
total:
                break
        del self.threadCallQueue[:count]
        if self.threadCallQueue:
            self.wakeUp()

# insert new delayed
calls now
    self._insertNewDelayedCalls()

now = self.seconds()
while self._pendingTimedCalls and (self._pendingTimedCalls[0].time
<= now):
    call = heappop(self._pendingTimedCalls)
    if call.cancelled:
        self._cancellations-=1
        continue

if call.delayed_time
> 0:
        call.activate_delay()
        heappush(self._pendingTimedCalls,
call)
        continue

try:
        call.called = 1
        call.func(*call.args,
**call.kw)
    except:
        log.deferr()
        if hasattr(call, "creator"):
            e = "\n"
            e += " C:
previous exception occurred in " + \
                 "a DelayedCall
created here:\n"
            e += "
C:"
            e += "".join(call.creator).rstrip().replace("\n","\n C:")
            e += "\n"
            log.msg(e)

if (self._cancellations > 50 and
     self._cancellations
> len(self._pendingTimedCalls) >> 1):
    self._cancellations
= 0
    self._pendingTimedCalls
= [x for x in self._pendingTimedCalls
                               if not x.cancelled]
    heapify(self._pendingTimedCalls)

if self._justStopped:
    self._justStopped
= False
    self.fireSystemEvent("shutdown")

进入self._insertNewDelayedCalls()

def _insertNewDelayedCalls(self):
    for call in self._newTimedCalls:
        if call.cancelled:
            self._cancellations-=1
        else:
            call.activate_delay()
            heappush(self._pendingTimedCalls,
call)
    self._newTimedCalls
= []

从self._newTimedCalls中获取DelayedCall()实例，放入self._pendingTimedCalls

在runUntilCurrent中会调用self._pendingTimedCallsk列表相关对象，也就是执行func_1.

2.     
其它

2.1.   
代码解析1

heappush(self._pendingTimedCalls,
call)

函数heappush源自heapq.py

def heappush(heap, item):
    """Push
item onto heap, maintaining the heap invariant."""
    heap.append(item)
    _siftdown(heap, 0, len(heap)-1)

简单点说，它会构建一个有序堆，默认最小堆。

在构建有序堆过程中肯定是要比较int类型了，但call是一个类。

这里要回顾python类的特殊方法了，已有文档，不赘述。

call是DelayedCall类的实例，查看相关代码。

def __le__(self, other):
    """
    Implement C{<=} operator between
two L{DelayedCall} instances.

Comparison is based on the C{time}
attribute (unadjusted by the
    delayed time).
    """
    return self.time
<= other.time

def __lt__(self, other):
    """
    Implement C{<} operator between
two L{DelayedCall} instances.

Comparison is based on the C{time}
attribute (unadjusted by the
    delayed time).
    """
    return self.time
< other.time