bottle-tornado-hybrid

Hybrid approach for existing wsgi python bottle application to use asyncio tornado handlers for websocket

Background

I have worked number of bottle applications using various backends (cherrypy, gunicorn, tornado).

Some application would like to support web-socket.

This example explores how you can directly add TornadoWebSocketHandlers to the underlying TornadoServer whilst still supporting an existing application that is written using bottle.

import bottle
import tornado
import tornado.websocket
import tornado.web


@bottle.route("/")
def bottle_homepage():
    return """
<ul>
    <li><a href='bottle-hello'>bottle-hello</a></li>    
    <li><a href='tornado-hello'>tornado-hello</a></li>
    <li><a href='test-ws'>test-ws</a></li>
</ul>"""


@bottle.route("/bottle-hello")
def bottle_hello():
    return "Hello from bottle"


@bottle.route("/test-ws")
def bottle_test_websocket():
    return """<script>
var ws = new WebSocket('ws://localhost:8080/tornado-ws')
ws.onopen = (msg)=>{ws.send('Hello Hybrid');}
    </script>
    """


class WSHandler(tornado.websocket.WebSocketHandler):
    def open(self):
        print("new connection")
        self.write_message("New Connection")

    def on_message(self, message):
        print("message received %s" % message)
        self.write_message("Hello World")

    def on_close(self):
        print("connection closed")


class TornadoHelloHandler(tornado.web.RequestHandler):
    def get(self):
        self.write("Hello from tornado")


class TornadoServerWithHandlers(bottle.ServerAdapter):
    def run(self, bottle_app):
        import tornado.wsgi
        import tornado.httpserver
        import tornado.ioloop

        wsgi_app = tornado.wsgi.WSGIContainer(bottle_app)
        tornado_handler_routes = list(self.options.get("tornado_handler_routes") or [])
        tornado_handler_routes.append(
            (".*", tornado.web.FallbackHandler, dict(fallback=wsgi_app))
        )

        tornado_app = tornado.web.Application(tornado_handler_routes)
        server = tornado.httpserver.HTTPServer(tornado_app)
        server.listen(self.port, address=self.host)
        tornado.ioloop.IOLoop.instance().start()


if __name__ == "__main__":
    tornado_handler_routes = [
        ("/tornado-hello", TornadoHelloHandler),
        ("/tornado-ws", WSHandler),
    ]
    bottle.run(
        host="localhost",
        port=8080,
        server=TornadoServerWithHandlers,
        tornado_handler_routes=tornado_handler_routes,
    )