如何异步使用Tornado和Redis？

Question

我在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() 

我需要获得访问/ URL，并获得了“Hello World”的同时，有一个在/wait挂起的请求。 我该怎么办？

Answer 1

您不应该在主龙卷风线程中使用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，但您应该创建一个单独的线程来监听Redis。当您收到消息时，您可以使用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。

有几个人可用，toredis，brukva等

下面是toredis发布订阅例如：https://github.com/mrjoes/toredis/blob/master/tests/test_handler.py

Answer 3

好了，所以这是我的我怎么会用GET请求做例子。

我增加两个主要组件：

首先是一个简单的螺纹发布订阅监听器，追加新的消息到本地列表对象。 我还向类中添加了列表访问器，因此您可以像监听器线程一样从常规列表中读取数据。就您的WebRequest而言，您只是从本地列表对象读取数据。这会立即返回，并且不会阻止当前请求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。这是继承了Web请求类的辅助对象，以便添加功能和属性。在这种情况下，它会检查通道侦听器是否已存在所请求的通道，如果找不到任何通道侦听器，则会创建一个，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类现在把听者仿佛它是一个静态列表（铭记你需要给self.write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，创建应用程序后，我加入一个空的字典作为一个属性

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

除了正在运行的线程的一些清理，一旦你退出应用程序

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

的完整代码：

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() 

Answer 4

对于Python> = 3。3，我建议你使用aioredis。 我没有测试下面的代码，但它应该是类似的东西：

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()