如何异步使用Tornado和Redis？

Question

我试图找到如何异步使用Redis和Tornado。 我找到了tornado-redis，但我需要的不仅仅是在代码中添加一个yield 。

我有以下代码：

import redis
import tornado.web

class WaiterHandler(tornado.web.RequestHandler):

    @tornado.web.asynchronous
    def get(self):
        client = redis.StrictRedis(port=6279)
        pubsub = client.pubsub()
        pubsub.subscribe('test_channel')

        for item in pubsub.listen():
            if item['type'] == 'message':
                print item['channel']
                print item['data']

        self.write(item['data'])
        self.finish()


class GetHandler(tornado.web.RequestHandler):

    def get(self):
        self.write("Hello world")


application = tornado.web.Application([
    (r"/", GetHandler),
    (r"/wait", WaiterHandler),
])

if __name__ == '__main__':
    application.listen(8888)
    print 'running'
    tornado.ioloop.IOLoop.instance().start()

我需要访问/ url并获取“Hello World”，而/wait有一个待处理的请求。 我该怎么做？

Answer 1

您不应该在主Tornado线程中使用Redis pub / sub，因为它会阻止IO循环。 您可以在主线程中处理来自Web客户端的长轮询，但是您应该创建一个单独的线程来侦听Redis。 然后，您可以在收到消息时使用ioloop.add_callback()和/或threading.Queue与主线程进行通信。

Answer 2

您需要使用Tornado IOLoop兼容的redis客户端。

其中很少有， toredis ， brukva等。

这是toredis中的pubsub示例： https ： //github.com/mrjoes/toredis/blob/master/tests/test_handler.py

Answer 3

对于Python> = 3.3，我建议你使用aioredis 。 我没有测试下面的代码，但它应该是这样的：

import redis
import tornado.web
from tornado.web import RequestHandler

import aioredis
import asyncio
from aioredis.pubsub import Receiver


class WaiterHandler(tornado.web.RequestHandler):

    @tornado.web.asynchronous
    def get(self):
        client = await aioredis.create_redis((host, 6279), encoding="utf-8", loop=IOLoop.instance().asyncio_loop)

        ch = redis.channels['test_channel']
        result = None
        while await ch.wait_message():
            item = await ch.get()
            if item['type'] == 'message':
                print item['channel']
                print item['data']
                result = item['data']

        self.write(result)
        self.finish()


class GetHandler(tornado.web.RequestHandler):

    def get(self):
        self.write("Hello world")


application = tornado.web.Application([
    (r"/", GetHandler),
    (r"/wait", WaiterHandler),
])

if __name__ == '__main__':
    print 'running'
    tornado.ioloop.IOLoop.configure('tornado.platform.asyncio.AsyncIOLoop')
    server = tornado.httpserver.HTTPServer(application)
    server.bind(8888)
    # zero means creating as many processes as there are cores.
    server.start(0)
    tornado.ioloop.IOLoop.instance().start()

Answer 4

好的，所以这是我的例子，我将如何处理获取请求。

我添加了两个主要组件：

第一个是简单的线程pubsub侦听器，它将新消息附加到本地列表对象中。 我还为类添加了列表访问器，因此您可以从侦听器线程中读取，就像您从常规列表中读取一样。 就WebRequest而言，您只是从本地列表对象中读取数据。 这会立即返回，并且不会阻止当前请求被完成或将来的请求被接受和处理。

class OpenChannel(threading.Thread):
    def __init__(self, channel, host = None, port = None):
        threading.Thread.__init__(self)
        self.lock = threading.Lock()
        self.redis = redis.StrictRedis(host = host or 'localhost', port = port or 6379)
        self.pubsub = self.redis.pubsub()
        self.pubsub.subscribe(channel)

        self.output = []

    # lets implement basic getter methods on self.output, so you can access it like a regular list
    def __getitem__(self, item):
        with self.lock:
            return self.output[item]

    def __getslice__(self, start, stop = None, step = None):
        with self.lock:
            return self.output[start:stop:step]

    def __str__(self):
        with self.lock:
            return self.output.__str__()

    # thread loop
    def run(self):
        for message in self.pubsub.listen():
            with self.lock:
                self.output.append(message['data'])

    def stop(self):
        self._Thread__stop()

第二个是ApplicationMixin类。 这是您的Web请求类继承的辅助对象，以便添加功能和属性。 在这种情况下，它检查所请求的通道是否已存在通道侦听器，如果找不到通道侦听器，则创建一个通道侦听器，并将侦听器句柄返回给WebRequest。

# add a method to the application that will return existing channels
# or create non-existing ones and then return them
class ApplicationMixin(object):
    def GetChannel(self, channel, host = None, port = None):
        if channel not in self.application.channels:
            self.application.channels[channel] = OpenChannel(channel, host, port)
            self.application.channels[channel].start()
        return self.application.channels[channel]

WebRequest类现在将侦听器视为静态列表（请记住，您需要为self.write一个字符串）

class ReadChannel(tornado.web.RequestHandler, ApplicationMixin):
    @tornado.web.asynchronous
    def get(self, channel):
        # get the channel
        channel = self.GetChannel(channel)
        # write out its entire contents as a list
        self.write('{}'.format(channel[:]))
        self.finish() # not necessary?

最后，在创建应用程序之后，我添加了一个空字典作为属性

# add a dictionary containing channels to your application
application.channels = {}

一旦退出应用程序，以及正在运行的线程的一些清理

# clean up the subscribed channels
for channel in application.channels:
    application.channels[channel].stop()
    application.channels[channel].join()

完整的代码：

import threading
import redis
import tornado.web



class OpenChannel(threading.Thread):
    def __init__(self, channel, host = None, port = None):
        threading.Thread.__init__(self)
        self.lock = threading.Lock()
        self.redis = redis.StrictRedis(host = host or 'localhost', port = port or 6379)
        self.pubsub = self.redis.pubsub()
        self.pubsub.subscribe(channel)

        self.output = []

    # lets implement basic getter methods on self.output, so you can access it like a regular list
    def __getitem__(self, item):
        with self.lock:
            return self.output[item]

    def __getslice__(self, start, stop = None, step = None):
        with self.lock:
            return self.output[start:stop:step]

    def __str__(self):
        with self.lock:
            return self.output.__str__()

    # thread loop
    def run(self):
        for message in self.pubsub.listen():
            with self.lock:
                self.output.append(message['data'])

    def stop(self):
        self._Thread__stop()


# add a method to the application that will return existing channels
# or create non-existing ones and then return them
class ApplicationMixin(object):
    def GetChannel(self, channel, host = None, port = None):
        if channel not in self.application.channels:
            self.application.channels[channel] = OpenChannel(channel, host, port)
            self.application.channels[channel].start()
        return self.application.channels[channel]

class ReadChannel(tornado.web.RequestHandler, ApplicationMixin):
    @tornado.web.asynchronous
    def get(self, channel):
        # get the channel
        channel = self.GetChannel(channel)
        # write out its entire contents as a list
        self.write('{}'.format(channel[:]))
        self.finish() # not necessary?


class GetHandler(tornado.web.RequestHandler):

    def get(self):
        self.write("Hello world")


application = tornado.web.Application([
    (r"/", GetHandler),
    (r"/channel/(?P<channel>\S+)", ReadChannel),
])


# add a dictionary containing channels to your application
application.channels = {}


if __name__ == '__main__':
    application.listen(8888)
    print 'running'
    try:
        tornado.ioloop.IOLoop.instance().start()
    except KeyboardInterrupt:
        pass

    # clean up the subscribed channels
    for channel in application.channels:
        application.channels[channel].stop()
        application.channels[channel].join()