CORS reverse development proxy

A simple yet extensible python wrapper script for templating a proxy nginx configuration that functions as host mapped reverse proxy container.

Why and when to use?

Modern browsers enforce CORS policy and won't let you make requests from your frontend running on localhost:8080 to your backend at localhost:4000. To solve this problem, start a proxy at localhost:5000 (or any other spare port) and proxy requests based on paths:

• localhost:5000/api and localhost:5000/buy will be routed to the backend localhost:4000
• localhost:5000/ will be routed to the frontend localhost:8080

Installation and usage

pip install proxybootstrap # using pip

Note: You will need docker for running the proxy container

Start the proxy server with your configuration

proxybootstrap \
    --port 5000 \
    /api@http://127.0.0.1:4000 /buy@http://127.0.0.1:4000 /@http://127.0.0.1:8080

Customization

Option	Description	Default
locations	service locations to proxy.	None
-c / -config	nginx config template file	./config/default.conf
--port	listening port for the reverse proxy	5000
--verbose	enable verbose output	False
--sync	force synchronous communication with the proxy	False
--tag	docker tag for the reverse proxy container	dev/cors-reverse-proxy
--dockerfile	dockerfile for building the container	./Dockerfile

Under the hood, configuration options are applied to the --config template file and rendered using jinja2. If you wish, you can pass additional arguments and use them in the config template. Example:

proxybootstrap \
    -my_var1 Test1 \
    --my_var2 Test2 \
    --port 5000 \
    /@http://127.0.0.1:8080

can be accessed in a template with

{{ my_var1 }}
{{ my_var2 }}

Alternatives

• Write a custom proxy configuration for nginx or other proxy servers like trafik, envoy or haproxy
• When using webpack or another popular tool there might be some plugins like devserver-proxy for vuejs
• Mess around with headers to allow specific CORS requests

Development

If you do not have pipx and pipenv, install with

python3 -m pip install --user pipx
python3 -m pipx ensurepath
pipx install pipenv

Install all dependencies with

pipenv install --dev

To format, sort imports and check PEP8 conformity, run

pipenv run black .
pipenv run isort
pipenv run flake8

(These are also configured as a git pre commit hook)

Notice

This configuration is very minimal and intended for development use only.