100% cpu usage problem

[aiden0z]

The _process_incoming_data may cause 100% cpu usage problem when read data from bad socket fd.

    def _process_incoming_data(self):
        """Retrieve and process any incoming data.
        :return:
        """
        while self._running.is_set():
            if self.poller.is_ready:
                self.data_in += self._receive()
                self.data_in = self._on_read_impl(self.data_in)

1. py-spy output

2. get the problem thread

3. strace found select syscall return immediately and recvfrom syscall read zero data.

We should check the received data length to fix the dead loop problem.

Ref: The Redis client how to check the received data length. https://github.com/redis/redis-py/blob/16cfcc7fced84d2b53edf95af1c40b230b30fc3d/redis/connection.py#L435

[eandersson]

Thanks @aiden0z !