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#!/usr/bin/env python
#
# Copyright 2009 Facebook
#
# Licensed under the Apache License, Version 2.0 (the "License"); you may
# not use this file except in compliance with the License. You may obtain
# a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
# License for the specific language governing permissions and limitations
# under the License.
import logging
import tornado.escape
import tornado.ioloop
import tornado.web
import os.path
import uuid
from tornado.concurrent import Future
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)
define("debug", default=False, help="run in debug mode")
class MessageBuffer(object):
def __init__(self):
self.waiters = set()
self.cache = []
self.cache_size = 200
def wait_for_messages(self, cursor=None):
# Construct a Future to return to our caller. This allows
# wait_for_messages to be yielded from a coroutine even though
# it is not a coroutine itself. We will set the result of the
# Future when results are available.
result_future = Future()
if cursor:
new_count = 0
for msg in reversed(self.cache):
if msg["id"] == cursor:
break
new_count += 1
if new_count:
result_future.set_result(self.cache[-new_count:])
return result_future
self.waiters.add(result_future)
return result_future
def cancel_wait(self, future):
self.waiters.remove(future)
# Set an empty result to unblock any coroutines waiting.
future.set_result([])
def new_messages(self, messages):
logging.info("Sending new message to %r listeners", len(self.waiters))
for future in self.waiters:
future.set_result(messages)
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 MainHandler(tornado.web.RequestHandler):
def get(self):
self.render("index.html", messages=global_message_buffer.cache)
class MessageNewHandler(tornado.web.RequestHandler):
def post(self):
message = {
"id": str(uuid.uuid4()),
"body": self.get_argument("body"),
}
# to_basestring is necessary for Python 3's json encoder,
# which doesn't accept byte strings.
message["html"] = tornado.escape.to_basestring(
self.render_string("message.html", message=message))
if self.get_argument("next", None):
self.redirect(self.get_argument("next"))
else:
self.write(message)
global_message_buffer.new_messages([message])
class MessageUpdatesHandler(tornado.web.RequestHandler):
@gen.coroutine
def post(self):
cursor = self.get_argument("cursor", None)
# Save the future returned by wait_for_messages so we can cancel
# it in wait_for_messages
self.future = global_message_buffer.wait_for_messages(cursor=cursor)
messages = yield self.future
if self.request.connection.stream.closed():
return
self.write(dict(messages=messages))
def on_connection_close(self):
global_message_buffer.cancel_wait(self.future)
def main():
parse_command_line()
app = tornado.web.Application(
[
(r"/", MainHandler),
(r"/a/message/new", MessageNewHandler),
(r"/a/message/updates", MessageUpdatesHandler),
],
cookie_secret="__TODO:_GENERATE_YOUR_OWN_RANDOM_VALUE_HERE__",
template_path=os.path.join(os.path.dirname(__file__), "templates"),
static_path=os.path.join(os.path.dirname(__file__), "static"),
xsrf_cookies=True,
debug=options.debug,
)
app.listen(options.port)
tornado.ioloop.IOLoop.current().start()
if __name__ == "__main__":
main()
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