ChannelLayerManager

在获取DEFAULT没有时，引入设置中的backend_class，调用backend_class(**config)，之后返回

BaseChannelLayer

def __init__(self, expiry=60, capacity=100, channel_capacity=None):
    self.expiry = expiry
    self.capacity = capacity
    self.channel_capacity = channel_capacity or {}

InMemoryChannelLayer

def __init__(
    self,
    expiry=60,
    group_expiry=86400,
    capacity=100,
    channel_capacity=None,
    **kwargs
):
    super().__init__(
        expiry=expiry,
        capacity=capacity,
        channel_capacity=channel_capacity,
        **kwargs
    )
    self.channels = {}
    self.groups = {}
    self.group_expiry = group_expiry

加入组

async def group_add(self, group, channel):
    self.groups.setdefault(group, {})
    self.groups[group][channel] = time.time()

退出组

async def group_discard(self, group, channel):
    if group in self.groups:
        if channel in self.groups[group]:
            del self.groups[group][channel]
        if not self.groups[group]:
            del self.groups[group]

发送消息

async def group_send(self, group, message):
    self._clean_expired()
    # Send to each channel
    for channel in self.groups.get(group, set()):
        try:
            await self.send(channel, message)
        except ChannelFull:
            pass

在每个consumer的实现中，已经监听了附带了channel_name的receive，这里发送之后，再看reve