Okay, so here's my example of how I would do it with get requests.
I added two main components:
The first is a simple threaded pubsub listener which appends new messages into a local list object.
I also added list accessors to the class, so you can read from the listener thread as if you were reading from a regular list. As far as your `WebRequest` is concerned, you're just reading data from a local list object. This returns immediately and doesn't block current request from completing or future requests from being accepted and processed.
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()
The second is the ApplicationMixin class. This a secondary object you have your web request class inherit in order to add functionality and attributes. In this case it checks whether a channel listener already exists for the requested channel, creates one if none was found, and returns the listener handle to the 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]
The WebRequest class now treats the listener as if it were a static list (bearing in mind that you need to give `self.write` a string)
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?
Finally, after application is created, I added an empty dictionary as an attribute
# add a dictionary containing channels to your application
application.channels = {}
As well as some cleanup of the running threads, once you exit the application
# clean up the subscribed channels
for channel in application.channels:
application.channels[channel].stop()
application.channels[channel].join()
**The complete code:**
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()
]
