Getting Tornado to return HTTP 400 on all unused URLs

Question

Getting Tornado to return HTTP 400 on all unused URLs

2.1k Views Asked by Jules At 15 November 2025 at 22:08

Is it possible to set up a Tornado server to run on a certain port, actively serving an API at several URLs, and having it return an HTTP 400: Bad request on every other URL requested on that port?

Say for example that I've got a simple GET and POST API running on http://example.com:1234/get and http://example.com:1234/post respectively that return 2xx statuses as appropriate, but requests to http://example.com:1234/someRandomUrlRequest return an HTTP 400.

Original Q&A

There are 1 best solutions below

**A. Jesse Jiryu Davis** · Accepted Answer

Put a catch-all URL route at the end of your application's list of routes. Make a handler for that catch-all route that raises HTTPError(400) for GET and POST requests. Here's an example:

import tornado.ioloop
import tornado.web


class GetHandler(tornado.web.RequestHandler):
    def get(self):
        self.write("GetHandler\n")


class PostHandler(tornado.web.RequestHandler):
    def post(self):
        self.write("PostHandler\n")


class BadRequestHandler(tornado.web.RequestHandler):
    def get(self):
        raise tornado.web.HTTPError(400)

    post = get

application = tornado.web.Application([
    (r"/get", GetHandler),
    (r"/post", PostHandler),
    (r"/.*", BadRequestHandler),
])

if __name__ == "__main__":
    application.listen(1234)
    tornado.ioloop.IOLoop.instance().start()

Testing this with curl:

$ curl localhost:1234/get
GetHandler
$ curl --data 'foo' localhost:1234/post
PostHandler
$ curl localhost:1234
<html><title>400: Bad Request</title><body>400: Bad Request</body></html>
$ curl localhost:1234/adsf
<html><title>400: Bad Request</title><body>400: Bad Request</body></html>
$ curl --data 'foo' localhost:1234/adsf
<html><title>400: Bad Request</title><body>400: Bad Request</body></html>

Getting Tornado to return HTTP 400 on all unused URLs

There are 1 best solutions below

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