# 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 }

Da wir für unsere Anwendung einen Proxy mit dem Pfadpräfix `/api/v1` haben, muss das Frontend das OpenAPI-Schema unter `/api/v1/openapi.json` abrufen.

```mermaid
graph LR

browser("Browser")
proxy["Proxy auf http://0.0.0.0:9999/api/v1/app"]
server["Server auf http://127.0.0.1:8000/app"]

browser --> proxy
proxy --> server
```

/// tip | Tipp

Porque tenemos un proxy con un prefijo de path de `/api/v1` para nuestra aplicación, el frontend necesita obtener el esquema de OpenAPI en `/api/v1/openapi.json`.

```mermaid
graph LR

browser("Navegador")
proxy["Proxy en http://0.0.0.0:9999/api/v1/app"]
server["Servidor en http://127.0.0.1:8000/app"]

browser --> proxy
proxy --> server
```

/// tip | Consejo

↩️ 👥 ✔️ 🗳 ⏮️ ➡ 🔡 `/api/v1` 👆 📱, 🕸 💪 ☕ 🗄 🔗 `/api/v1/openapi.json`.

```mermaid
graph LR

browser("Browser")
proxy["Proxy on http://0.0.0.0:9999/api/v1/app"]
server["Server on http://127.0.0.1:8000/app"]

browser --> proxy
proxy --> server
```

/// tip

📢 `0.0.0.0` 🛎 ⚙️ ⛓ 👈 📋 👂 🔛 🌐 📢 💪 👈 🎰/💽.

///

这是因为应用使用了以 `/api/v1` 为路径前缀的代理，前端要从 `/api/v1/openapi.json`  中提取 OpenAPI 概图。

```mermaid
graph LR

browser("Browser")
proxy["Proxy on http://0.0.0.0:9999/api/v1/app"]
server["Server on http://127.0.0.1:8000/app"]

browser --> proxy
proxy --> server
```

/// tip | 提示

IP `0.0.0.0` 常用于指程序监听本机或服务器上的所有有效 IP。

///

API 文档还需要 OpenAPI 概图声明 API `server` 位于 `/api/v1`（使用代理时的 URL）。例如：

    private const val PROXY_A_HOST = "proxya"
    private val proxyA =
      Proxy(
        Proxy.Type.HTTP,
        InetSocketAddress.createUnresolved(PROXY_A_HOST, PROXY_A_PORT),
      )

    private const val PROXY_B_PORT = 1002
    private const val PROXY_B_HOST = "proxyb"
    private val proxyB =
      Proxy(
        Proxy.Type.HTTP,

    }

    return Selection(routes)
  }

  /** Prepares the proxy servers to try. */
  private fun resetNextProxy(
    url: HttpUrl,
    proxy: Proxy?,
  ) {
    fun selectProxies(): List<Proxy> {
      // If the user specifies a proxy, try that and only that.
      if (proxy != null) return listOf(proxy)

      // If the URI lacks a host (as in "http://</"), don't call the ProxySelector.

package okhttp3

import java.net.InetSocketAddress
import java.net.Proxy
import okhttp3.internal.toCanonicalHost

/**
 * The concrete route used by a connection to reach an abstract origin server. When creating a
 * connection the client has many options:
 *
 *  * **HTTP proxy:** a proxy server may be explicitly configured for the client. Otherwise, the

                    }

                    Proxy p = new Proxy();
                    p.setHost(proxy.getHost());
                    p.setProtocol(proxy.getProtocol());
                    p.setPort(proxy.getPort());
                    p.setNonProxyHosts(proxy.getNonProxyHosts());
                    p.setUserName(proxy.getUsername());
                    p.setPassword(proxy.getPassword());

    assertEquals(LIST1, ImmutableList.copyOf(newDelegatingListWithEquals(LIST1)));
  }

  public void testToString() {
    List<String> proxy = newDelegatingList(LIST1);
    assertEquals(Proxy.getInvocationHandler(proxy).toString(), proxy.toString());
  }

  interface A {}

  interface B {}

  public void testEquals() {
    new EqualsTester()
        .addEqualityGroup(newDelegatingList(LIST1))