如何在龍卷風中使用多個ioloop並在ioloop之間共享數據？

Question

我有一個Beaglebone Black連接到CAN總線設備：電池。

在Beaglebone Black上運行的龍卷風網作為GUI。

CAN總線讀取循環不斷從CAN總線讀取數據以更新Battery實例的狀態

但是，如何使兩個IOLOOP一起工作並共享Battery實例呢？

龍卷風網：

class Battery(object):
    status = {}



class API_Handler(web.RequestHandler):
    def get(self, dev, cmd):
        if cmd == 'data':
            self.write(self.application.battery0.status)


class Application(web.Application):
    def __init__(self):

        self.battery0 = Battery('bat0')    

        routing = [
            (r'/api/battery/(data|)', API_Handler),
        ]

        settings = {
            'template_path': os.path.join(os.path.dirname(__file__), "templates"),
            'static_path': os.path.join(os.path.dirname(__file__), "static"),
        }

        web.Application.__init__(self, routing, debug=True, **settings)


if __name__ == "__main__":
    import tornado

    app = Application()
    app.listen(address='0.0.0.0', port=8888)
    tornado.ioloop.IOLoop.instance().start()

CAN總線讀取循環，代碼：

#!/usr/bin/env python
# -*- coding: utf-8 -*-
import errno
import functools
import tornado.ioloop
import socket
import struct


can_frame_fmt = "=IB3x8s"
can_frame_size = struct.calcsize(can_frame_fmt)

def build_can_frame(can_id, data):
    can_dlc = len(data)
    data = data.ljust(8, b'\x00')
    return struct.pack(can_frame_fmt, can_id, can_dlc, data)

def dissect_can_frame(frame):
    can_id, can_dlc, data = struct.unpack(can_frame_fmt, frame)
    return (can_id, can_dlc, data[:can_dlc])

def connection_ready(sock, fd, events):
    while True:
        try:
            cf, addr = sock.recvfrom(can_frame_size)
        except socket.error as e:
            if e.args[0] not in (errno.EWOULDBLOCK, errno.EAGAIN):
                raise
            return
        dissect_can_frame(cf)


if __name__ == '__main__':
    sock = socket.socket(socket.AF_CAN, socket.SOCK_RAW, socket.CAN_RAW)
    sock.bind(('can0',))
    sock.setblocking(0)

    io_loop = tornado.ioloop.IOLoop.current()
    callback = functools.partial(connection_ready, sock)
    io_loop.add_handler(sock.fileno(), callback, io_loop.READ)
    io_loop.start()

Answer 1

如我所見，您正在運行兩個應用程序，因此很難共享Battery實例。 第一個解決方案-將所有功能組合在一個應用程序中，這樣就可以輕松使用Battery實例，但是在HTTP請求和在一個ioloop中處理來自CAN的套接字事件時，您將面臨挑戰。

因此，這是另一種解決方案，保留兩個應用程序，但不嘗試共享Battery實例，僅從CAN偵聽器向您的GUI應用程序發出http請求。

例如在CAN文件中：

from tornado.httpclient import AsyncHTTPClient

...

def connection_ready(sock, fd, events):
    while True:
        try:
           cf, addr = sock.recvfrom(can_frame_size)
        except socket.error as e:
            if e.args[0] not in (errno.EWOULDBLOCK, errno.EAGAIN):
                raise
            return
        http_client = AsyncHTTPClient()
        http_client.fetch("http://localhost:8888/update-battery",
                          method="POST",
                          body="can_id={}&can_dlc={}&data={}".format(
                              dissect_can_frame(cf)))

如果您的數據中有字節，最好使用python urllib中的 urlencode 編碼正文 。

在GUI文件中：

class Battery_Update_Handler(web.RequestHandler):
    def post(self):
        self.application.battery0.status = dict(
            can_id=self.get_argument("can_id", None),
            can_dlc=self.get_argument("can_dlc", None),
            data=self.get_argument("data", None))


class Application(web.Application):
    def __init__(self):

        self.battery0 = Battery('bat0')    

        routing = [
            (r'/api/battery/(data|)', API_Handler),
            (r'/update-battery', Battery_Update_Handler)
        ]

        settings = {
            'template_path': os.path.join(os.path.dirname(__file__), "templates"),
            'static_path': os.path.join(os.path.dirname(__file__), "static"),
        }

        web.Application.__init__(self, routing, debug=True, **settings)