* Restarts
* Replication (the number of processes running)
* Memory
* Previous steps before starting

In these cases you can use `root_path` to configure your application.

The `root_path` is a mechanism provided by the ASGI specification (that FastAPI is built on, through Starlette).

The `root_path` is used to handle these specific cases.

And it's also used internally when mounting sub-applications.

## Proxy with a stripped path prefix

### Internal

* 🔧 Update sponsors badge, course bundle. PR [#3340](https://github.com/tiangolo/fastapi/pull/3340) by [@tiangolo](https://github.com/tiangolo).
* 🔧 Add new gold sponsor Jina 🎉. PR [#3291](https://github.com/tiangolo/fastapi/pull/3291) by [@tiangolo](https://github.com/tiangolo).

* **Cloud services** that handle this for you

## Handling disconnections and multiple clients

When a WebSocket connection is closed, the `await websocket.receive_text()` will raise a `WebSocketDisconnect` exception, which you can then catch and handle like in this example.

=== "Python 3.9+"

    ```Python hl_lines="79-81"
    {!> ../../../docs_src/websockets/tutorial003_py39.py!}
    ```

=== "Python 3.8+"

    ```Python hl_lines="81-83"

    This command will be run from the **current working directory**, the same `/code` directory you set above with `WORKDIR /code`.

!!! tip
    Review what each line does by clicking each number bubble in the code. 👆

You should now have a directory structure like:

```
.
├── app
│   ├── __init__.py
│   └── main.py
├── Dockerfile
└── requirements.txt
```

!!! tip
    You can read more about it at <a href="https://12factor.net/config" class="external-link" target="_blank">The Twelve-Factor App: Config</a>.

### Types and validation

These environment variables can only handle text strings, as they are external to Python and have to be compatible with other programs and the rest of the system (and even with different operating systems, as Linux, Windows, macOS).