def idle_commands(self, delay, fds=None):nextsleep = delay                                                              #设置本函数的下次睡眠延迟                                                                  if not fds:fds = []for function, data in list(self._idlefuns.items()):                            #遍历_idlefuns，逐个调用其中的函数，注李意这里一个技巧，拷贝构造了_idlefuns列表，如果不拷贝直接使用，那么循环体内的删除操作将会出错try:retval = function(self, data, False)if retval is False:                                                    #函数返回值为False，也就是一个逻辑假的时候，从列表中删除这个函数，并设置nextsleep为Nonedel self._idlefuns[function]nextsleep = Noneelif retval is True:                                                   #函数返回值为True，也就是逻辑真的时候，设置nextsleep为None，注意这里不删除所调用的函数，那么我们可以理解为，一个函数被持续调用，直至其返回值为假nextsleep = Noneelif isinstance(retval, float) and nextsleep:                          #若返回值为浮点类型，那么认为这个函数返回的是一个时延，选择一个较小时延给nextsleepif (retval < nextsleep):nextsleep = retvalelif nextsleep is None:                                                #nextsleep为None，那么直接进入下一个函数的处理流程continueelse:                                                                  #否则认为函数返回一个文件描述符列表fds = fds + retvalexcept SystemExit:raiseexcept Exception as exc:if not isinstance(exc, bb.BBHandledException):logger.exception('Running idle function')del self._idlefuns[function]self.quit = True        #上面循环主要是做两件事：一件事是调用所有idlefunc，第二件是找到一个最小的nextsleep# Create new heartbeat event?now = time.time()if now >= self.next_heartbeat:                                            #当前事件比心跳时间迟，认为丢失了心跳# We might have missed heartbeats. Just trigger once in# that case and continue after the usual delay.self.next_heartbeat += self.heartbeat_secondsif self.next_heartbeat <= now:self.next_heartbeat = now + self.heartbeat_seconds                #计算出一个新的心跳延迟，保障新的心跳延迟一定是在将来heartbeat = bb.event.HeartbeatEvent(now)              bb.event.fire(heartbeat, self.cooker.data)                            #触发新的心跳if nextsleep and now + nextsleep > self.next_heartbeat:                   #睡眠以后可能错过新的心跳，因此这里缩短睡眠时间# Shorten timeout so that we we wake up in time for# the heartbeat.nextsleep = self.next_heartbeat - nowif nextsleep is not None:                                                 #在睡眠周期内找到可用的文件描述符，这里需要对select有一定了解if self.xmlrpc:nextsleep = self.xmlrpc.get_timeout(nextsleep)try:return select.select(fds,[],[],nextsleep)[0]except InterruptedError:# Ignore EINTRreturn []else:return select.select(fds,[],[],0)[0]

        fds = [self.sock]if self.xmlrpc:fds.append(self.xmlrpc)

    def __init__(self, lock, sock, sockname):multiprocessing.Process.__init__(self)self.command_channel = Falseself.command_channel_reply = Falseself.quit = Falseself.heartbeat_seconds = 1 # default, BB_HEARTBEAT_EVENT will be checked once we have a datastore.self.next_heartbeat = time.time()self.event_handle = Noneself.haveui = Falseself.lastui = Falseself.xmlrpc = Falseself._idlefuns = {}self.bitbake_lock = lockself.sock = sockself.sockname = socknamedef register_idle_function(self, function, data):"""Register a function to be called while the server is idle"""assert hasattr(function, '__call__')self._idlefuns[function] = data

    def _startServer(self):print(self.start_log_format % (os.getpid(), datetime.datetime.now().strftime(self.start_log_datetime_format)))server = ProcessServer(self.bitbake_lock, self.sock, self.sockname)self.configuration.setServerRegIdleCallback(server.register_idle_function)......cookerdata.py:    def setServerRegIdleCallback(self, srcb):        self.server_register_idlecallback = srcb