user: I have a dockerized React.js application that connects to a (also dockerized) backend written with actix-web in Rust. I have a development docker-compose file as well as a production one and am looking for a way to dynamically change the backend URL depending on the configuration in the frontend. What would be the most elegant way to achieve this? Note that environment variables are difficult in this situation, as they cannot be dynamically changed after the production frontend is built.

assistant: One solution to achieve this would be to use a reverse proxy like Nginx. You can set up Nginx in front of both your frontend and backend Docker containers, and then configure it to route requests to the correct container based on the URL. This would allow you to dynamically change the backend URL in your frontend code, and have Nginx route requests accordingly.

To do this, you would need to modify your docker-compose files to expose the ports for your frontend and backend containers to the host machine. Then, you can set up an Nginx container and mount a configuration file into it that specifies the routes to your frontend and backend containers. Within this configuration file, you can set up a proxy_pass directive that forwards requests to the appropriate backend container based on the URL path.

For example, your Nginx configuration file might look something like this:

```bash
server {
    listen 80;
    server_name example.com;

    location /api {
        proxy_pass http://backend:8000;
    }

    location / {
        proxy_pass http://frontend:3000;
    }
}
```

In this example, Nginx is configured to route requests to /api to the backend container at http://backend:8000, and all other requests to the frontend container at http://frontend:3000. You can then modify your frontend code to make requests to the /api path, and Nginx will route them to the correct backend container.

By using Nginx as a reverse proxy, you can dynamically change the backend URL in your frontend code without having to rebuild your production image. This provides a more elegant and scalable solution for managing your application's configuration.

user: Are there any alternatives to Nginx written using Rust?

assistant: Yes, there are some alternatives to Nginx that are written in Rust. Two popular options are:

1. Traefik: Traefik is a modern HTTP reverse proxy and load balancer that can automatically discover backends and route traffic to them. It has built-in support for Docker and Kubernetes, and can be used to dynamically route traffic based on container labels, service discovery, or other criteria. Traefik is written in Go, but it also has a Rust-based plugin system called Yaegi, which allows you to write plugins in Rust.

2. Caddy: Caddy is a fast, easy-to-use HTTP/2 web server and reverse proxy written in Go. It has a modern, lightweight design and supports automatic HTTPS, automatic Let's Encrypt certificate provisioning, and other features out of the box. Caddy also has a plugin system that allows you to extend its functionality. One of its plugins, called Proxy Protocol, allows you to easily set up a reverse proxy with TCP/IP headers.

While Nginx is the most popular option for reverse proxying and load balancing, both Traefik and Caddy are solid alternatives that can be used in a Rust-based infrastructure.