Can't serve swagger on remotely hosted server with different url

Question

I'm trying to serve some simple service using flask and flask_restx (a forked project of flask-restplus, that would be eventually served on AWS.

When it is served, I want to generate swagger page for others to test it easily.

from flask import Flask
from flask_restx import Api
from my_service import service_namespace

app = Flask(__name__)
api = Api(app, version='1.0')
api.add_namespace(service_namespace)

if __name__ == '__main__':

    app.run(debug=True)

When I test it locally (e.g. localhost:5000), it works just fine. Problem is, when it is hosted on AWS, because it has a specific domain (gets redirected?) (e.g. my-company.com/chris-service to a container), the document page is unable to find its required files like css and so:

What I've looked and tried

Python (Flask + Swagger) Flasgger throwing 404 error

flask python creating swagger document error

404 error in Flask

Also tried adding Blueprint (albeit without knowing exactly what it does):

app = Flask(__name__)
blueprint = Blueprint("api", __name__, 
                      root_path="/chris-service",
                      # url_prefix="/chris-service", # doesn't work
)
api = Api(blueprint)
app.register_blueprint(blueprint)
...

And still no luck.

Update

So here's more information as per the comments (pseudo, but technically identical)

1. Access point for the swagger is my-company.com/chris (with or without http:// or https:// doesn't make difference)
2. When connecting to the above address, the request URL for the assets are my-company.com/swaggerui/swagger-ui.css
3. You can access the asset in my-company.com/chris/swaggerui/swagger-ui.css
4. So I my resolution (which didn't work) was to somehow change the root_path (not even sure if it's the correct wording), as shown in What I've looked and tried.

I've spent about a week to solve this but can't find a way.

Any help will be greatful :) Thanks

Answer 1

Always very frustrating when stuff is working locally but not when deployed to AWS. Reading this github issue, these 404 errors on swagger assets are probably caused by:

1. Missing javascript swagger packages

Probably not the case, since flask-restx does this for you. And running it locally should also not work in this case.

2. Missing gunicorn settings

Make sure that you are also setting gunicorn up correctly as well with --forwarded-allow-ips if deploying with it (you should be). If you are in a kubernetes cluster you can set this to *

https://docs.gunicorn.org/en/stable/settings.html#forwarded-allow-ips

3. According to this post, you also have to explicitly set settings.FLASK_SERVER_NAME to something like http://ec2-10-221-200-56.us-west-2.compute.amazonaws.com:5000

4. If that does not work, try to deploy a flask-restx example, that should definetely work. This rules out any errors on your end.

Answer 2

Swagger parameters defined at apidoc.py file. Default apidoc object also created in this file. So if you want to customize it you have change it before app and api initialization.

In your case url_prefix should be changed (I recommend to use environment variables to be able set url_prefix flexibly):

$ export URL_PREFIX='/chris'

from os import environ
from flask import Flask
from flask_restx import Api, apidoc

if (url_prefix := environ.get('URL_PREFIX', None)) is not None:
    apidoc.apidoc.url_prefix = url_prefix

app = Flask(__name__)
api = Api(app)

...

if __name__ == '__main__':
    app.run()