server.py

import logging
import tornado.auth
import tornado.escape
import tornado.ioloop
import tornado.web
import os.path
import uuid
import datetime

from tornado import gen
from tornado.options import define, options, parse_command_line

define("port", default=8888, help="run on the given port", type=int)

class MessageBuffer(object):
    def __init__(self):
        self.waiters = set()
        self.cache = []
        self.cache_size = 200

    def wait_for_messages(self, callback, cursor=None):
        if cursor:
            new_count = 0
            for msg in reversed(self.cache):
                if msg["id"] == cursor:
                    break
                new_count += 1
            if new_count:
                callback(self.cache[-new_count:])
                return
        self.waiters.add(callback)

    def cancel_wait(self, callback):
        self.waiters.remove(callback)

    def new_messages(self, messages):
        logging.info("Sending new message to %r listeners", len(self.waiters))
        for callback in self.waiters:
            try:
                callback(messages)
            except:
                logging.error("Error in waiter callback", exc_info=True)
        self.waiters = set()
        self.cache.extend(messages)
        if len(self.cache) > self.cache_size:
            self.cache = self.cache[-self.cache_size:]


# Making this a non-singleton is left as an exercise for the reader.
global_message_buffer = MessageBuffer()


class BaseHandler(tornado.web.RequestHandler):
    def get_current_user(self):
        user_json = self.get_secure_cookie("chatdemo_user")
        if not user_json: return None
        return tornado.escape.json_decode(user_json)


class MainHandler(BaseHandler):
    def get(self):
        self.render("index.html", messages=global_message_buffer.cache)

def main():
    parse_command_line()
    app = tornado.web.Application(
        [
            (r"/", MainHandler),
            ],
        cookie_secret="__TODO:_GENERATE_YOUR_OWN_RANDOM_VALUE_HERE__",
        )
    app.listen(options.port)
    tornado.ioloop.IOLoop.instance().start()


if __name__ == "__main__":
    main()