By only using `BackgroundTasks` (and not `BackgroundTask`), it's then possible to use it as a *path operation function* parameter and have **FastAPI** handle the rest for you, just like when using the `Request` object directly.

It's still possible to use `BackgroundTask` alone in FastAPI, but you have to create the object in your code and return a Starlette `Response` including it.

    validations:
      required: true

  - type: input
    id: testgrid
    attributes:
      label: Testgrid link

  - type: textarea
    id: reason
    attributes:
      label: Reason for failure (if possible)

  - type: textarea
    id: additional
    attributes:
      label: Anything else we need to know?

  - type: textarea
    id: sigs
    attributes:
      label: Relevant SIG(s)

   * InputStream#skip(long) skip}, if possible) to the end of the stream and return the total number
   * of bytes that were read.
   *
   * <p>Note that for some sources that implement {@link #sizeIfKnown} to provide a more efficient
   * implementation, it is <i>possible</i> that this method will return a different number of bytes

   * response code like 404 or 500.
   *
   * @throws IOException if the request could not be executed due to cancellation, a connectivity
   *     problem or timeout. Because networks can fail during an exchange, it is possible that the
   *     remote server accepted the request before the failure.
   * @throws IllegalStateException when the call has already been executed.
   */
  @Throws(IOException::class)
  fun execute(): Response

0002 0.554 responseBodyEnd
0002 0.554 connectionReleased
0002 0.554 callEnd
0001 0.624 responseBodyEnd
0001 0.624 connectionReleased
0001 0.624 callEnd
```

The `EventListener.Factory` also makes it possible to limit metrics to a subset of calls. This one captures metrics on a random 10%:

```java
class MetricsEventListener extends EventListener {
  private static final Factory FACTORY = new Factory() {

In the end, the ultimate objective is to be able to **serve your API clients** in a way that is **secure**, to **avoid disruptions**, and to use the **compute resources** (for example remote servers/virtual machines) as efficiently as possible. 🚀

Par exemple, nous, l'équipe derrière FastAPI, avons créé [**FastAPI Cloud**](https://fastapicloud.com), pour rendre le déploiement d'applications FastAPI dans le cloud aussi fluide que possible, avec la même expérience développeur que lorsque vous travaillez avec FastAPI.

Je vais vous montrer certains des principaux concepts que vous devriez probablement avoir à l'esprit lors du déploiement

## Official Guide { #official-guide }

Pydantic has an official [Migration Guide](https://docs.pydantic.dev/latest/migration/) from v1 to v2.

It also includes what has changed, how validations are now more correct and strict, possible caveats, etc.

You can read it to understand better what has changed.

## Tests { #tests }

Make sure you have [tests](../tutorial/testing.md) for your app and you run them on continuous integration (CI).

		Method: http.MethodPost,
		URL:    u,
	}
	if !guessIsRPCReq(r) {
		t.Fatal("Test shouldn't fail for a possible net/rpc request.")
	}
	r = &http.Request{
		Proto:  "HTTP/1.1",
		Method: http.MethodGet,
		URL:    u,
	}
	if !guessIsRPCReq(r) {
		t.Fatal("Test shouldn't fail for a possible net/rpc request.")
	}
	r = &http.Request{
		Proto:  "HTTP/1.1",
		Method: http.MethodGet,

      description: "Please paste a screenshot of the page."
    validations:
      required: false
  - type: textarea
    id: what-did-you-do
    attributes:
      label: "What did you do?"
      description: "If possible, provide a recipe for reproducing the error. Starting with a Private/Incognito tab/window may help rule out problematic browser extensions."
    validations:
      required: true
  - type: textarea
    id: actual-behavior