// Define a single Proxy at myproxy:8008 that will artificially move during the test
    val proxySelector = RecordingProxySelector()
    val socketAddress = InetSocketAddress.createUnresolved("myproxy", 8008)
    proxySelector.proxies.add(Proxy(Proxy.Type.HTTP, socketAddress))

    // Define two host names for the DNS routing of fake proxy servers

# Behind a Proxy { #behind-a-proxy }

In many situations, you would use a **proxy** like Traefik or Nginx in front of your FastAPI app.

These proxies could handle HTTPS certificates and other things.

## Proxy Forwarded Headers { #proxy-forwarded-headers }

```mermaid
sequenceDiagram
    participant Client
    participant Proxy as Proxy/Loadbalancer
    participant Server as FastAPI Server

    Client->>Proxy: HTTPS-Request<br/>Host: mysuperapp.com<br/>Pfad: /items

    Note over Proxy: Proxy fügt Forwarded-Header hinzu

```mermaid
sequenceDiagram
    participant Client
    participant Proxy as Proxy/Load Balancer
    participant Server as FastAPI Server

    Client->>Proxy: HTTPS Request<br/>Host: mysuperapp.com<br/>Path: /items

    Note over Proxy: Proxy adds forwarded headers

```mermaid
sequenceDiagram
    participant Client as Cliente
    participant Proxy as Proxy/Load Balancer
    participant Server as Servidor de FastAPI

    Client->>Proxy: HTTPS Request<br/>Host: mysuperapp.com<br/>Path: /items

    Note over Proxy: El proxy añade headers reenviados

```mermaid
sequenceDiagram
    participant Client as Клиент
    participant Proxy as Прокси/Балансировщик нагрузки
    participant Server as FastAPI-сервер

    Client->>Proxy: HTTPS-запрос<br/>Host: mysuperapp.com<br/>Path: /items

    Note over Proxy: Прокси-сервер добавляет пересылаемые заголовки

Mark Theunissen <******@****.***> 1740597949 +0100

    }

    private static Proxy toProxy(org.apache.maven.repository.Proxy proxy) {
        Proxy result = null;
        if (proxy != null) {
            AuthenticationBuilder authBuilder = new AuthenticationBuilder();
            authBuilder.addUsername(proxy.getUserName()).addPassword(proxy.getPassword());
            result = new Proxy(proxy.getProtocol(), proxy.getHost(), proxy.getPort(), authBuilder.build());
        }

    * Otherwise, you might have to stop the TLS Termination Proxy momentarily, start the renewal program to acquire the certificates, then configure them with the TLS Termination Proxy, and then restart the TLS Termination Proxy. This is not ideal, as your app(s) will not be available during the time that the TLS Termination Proxy is off.

Todo este proceso de renovación, mientras aún se sirve la aplicación, es una de las principales razones por las que querrías tener un **sistema separado para gestionar el HTTPS** con un TLS Termination Proxy en lugar de simplemente usar los certificados TLS con el servidor de aplicaciones directamente (por ejemplo, Uvicorn).

## Headers reenviados por el proxy { #proxy-forwarded-headers }