tornado.wsgi — Interoperability with other Python frameworks and servers

WSGI support for the Tornado web framework.

WSGI is the Python standard for web servers, and allows for interoperability between Tornado and other Python web frameworks and servers. This module provides WSGI support in two ways:

  • WSGIAdapter converts a tornado.web.Application to the WSGI application interface. This is useful for running a Tornado app on another HTTP server, such as Google App Engine. See the WSGIAdapter class documentation for limitations that apply.
  • WSGIContainer lets you run other WSGI applications and frameworks on the Tornado HTTP server. For example, with this class you can mix Django and Tornado handlers in a single server.

Running Tornado apps on WSGI servers

class tornado.wsgi.WSGIAdapter(application)[source]

Converts a tornado.web.Application instance into a WSGI application.

Example usage:

import tornado.web
import tornado.wsgi
import wsgiref.simple_server

class MainHandler(tornado.web.RequestHandler):
    def get(self):
        self.write("Hello, world")

if __name__ == "__main__":
    application = tornado.web.Application([
        (r"/", MainHandler),
    wsgi_app = tornado.wsgi.WSGIAdapter(application)
    server = wsgiref.simple_server.make_server('', 8888, wsgi_app)

See the appengine demo for an example of using this module to run a Tornado app on Google App Engine.

In WSGI mode asynchronous methods are not supported. This means that it is not possible to use AsyncHTTPClient, or the tornado.auth or tornado.websocket modules.

In multithreaded WSGI servers on Python 3, it may be necessary to permit asyncio to create event loops on any thread. Run the following at startup (typically import time for WSGI applications):

import asyncio
from tornado.platform.asyncio import AnyThreadEventLoopPolicy

New in version 4.0.

Deprecated since version 5.1: This class is deprecated and will be removed in Tornado 6.0. Use Tornado’s HTTPServer instead of a WSGI container.

class tornado.wsgi.WSGIApplication(handlers=None, default_host=None, transforms=None, **settings)[source]

A WSGI equivalent of tornado.web.Application.

Deprecated since version 4.0: Use a regular Application and wrap it in WSGIAdapter instead. This class will be removed in Tornado 6.0.

Running WSGI apps on Tornado servers

class tornado.wsgi.WSGIContainer(wsgi_application)[source]

Makes a WSGI-compatible function runnable on Tornado’s HTTP server.


WSGI is a synchronous interface, while Tornado’s concurrency model is based on single-threaded asynchronous execution. This means that running a WSGI app with Tornado’s WSGIContainer is less scalable than running the same app in a multi-threaded WSGI server like gunicorn or uwsgi. Use WSGIContainer only when there are benefits to combining Tornado and WSGI in the same process that outweigh the reduced scalability.

Wrap a WSGI function in a WSGIContainer and pass it to HTTPServer to run it. For example:

def simple_app(environ, start_response):
    status = "200 OK"
    response_headers = [("Content-type", "text/plain")]
    start_response(status, response_headers)
    return ["Hello world!\n"]

container = tornado.wsgi.WSGIContainer(simple_app)
http_server = tornado.httpserver.HTTPServer(container)

This class is intended to let other frameworks (Django,, etc) run on the Tornado HTTP server and I/O loop.

The tornado.web.FallbackHandler class is often useful for mixing Tornado and WSGI apps in the same server. See for a complete example.

static environ(request)[source]

Converts a tornado.httputil.HTTPServerRequest to a WSGI environment.