<font color="#A6E22E">INFO</font>:     Waiting for application startup.
<font color="#A6E22E">INFO</font>:     Application startup complete.
```

</div>

The only new option here is `--workers` telling Uvicorn to start 4 worker processes.

You can also see that it shows the **PID** of each process, `27365` for the parent process (this is the **process manager**) and one for each worker process: `27368`, `27369`, `27370`, and `27367`.

        Set<PathType> pathTypes = dep.getType().getPathTypes();
        if (containsPatches(pathTypes)) {
            if (outputModules == null) {
                // For telling users that it is too late for setting the output directory.
                outputModules = PathModularization.NONE;
            }
            PathType type = null;
            for (Map.Entry<Path, String> info :

        Set<PathType> pathTypes = dep.getType().getPathTypes();
        if (containsPatches(pathTypes)) {
            if (outputModules == null) {
                // For telling users that it is too late for setting the output directory.
                outputModules = PathModularization.NONE;
            }
            PathType type = null;
            for (Map.Entry<Path, String> info :

{!../../../docs_src/handling_errors/tutorial005.py!}
```

Now try sending an invalid item like:

```JSON
{
  "title": "towel",
  "size": "XL"
}
```

You will receive a response telling you that the data is invalid containing the received body:

```JSON hl_lines="12-15"
{
  "detail": [
    {
      "loc": [
        "body",
        "size"
      ],

Nevertheless, you can still do it in **FastAPI**, using one of the internal tools from Starlette.

And the docs would still work, although not adding any documentation telling that the parameter should contain a path.

### Path convertor

Using an option directly from Starlette you can declare a *path parameter* containing a *path* using a URL like:

```
/files/{file_path:path}

If you added the return type annotation, tools and editors would complain with a (correct) error telling you that your function is returning a type (e.g. a dict) that is different from what you declared (e.g. a Pydantic model).

In those cases, you can use the *path operation decorator* parameter `response_model` instead of the return type.

        }

        ExecutorService createExecutor(int parallelism) {
            //
            // We need an executor that will not block.
            // We can't use work stealing, as we are building a graph
            // and this could lead to cycles where a thread waits for
            // a task to finish, then execute another one which waits
            // for the initial task...

If you are running your container behind a TLS Termination Proxy (load balancer) like Nginx or Traefik, add the option `--proxy-headers`, this will tell Uvicorn (through the FastAPI CLI) to trust the headers sent by that proxy telling it that the application is running behind HTTPS, etc.

```Dockerfile
CMD ["fastapi", "run", "app/main.py", "--proxy-headers", "--port", "80"]
```

#### Docker Cache

    ```

Notice that the default value is still `None`, so the parameter is still optional.

But now, having `Query(max_length=50)` inside of `Annotated`, we are telling FastAPI that we want it to extract this value from the query parameters (this would have been the default anyway 🤷) and that we want to have **additional validation** for this value (that's why we do this, to get the additional validation). 😎