When deploying applications you will probably want to have some **replication of processes** to take advantage of **multiple cores** and to be able to handle more requests.

As you saw in the previous chapter about [Deployment Concepts](concepts.md){.internal-link target=_blank}, there are multiple strategies you can use.

 *
 * <p>We have more thorough testing of {@code AtomicHelper} implementations in {@link
 * AggregateFutureStateFallbackAtomicHelperTest}. The advantage to this test is that it can run
 * under Android.
 */
@NullUnmarked
public class AggregateFutureStateDefaultAtomicHelperTest extends TestCase {
  public void testUsingExpectedAtomicHelper() throws Exception {

   * <p>Note: This default implementation is overkill (but valid) for an unordered container. An
   * equally valid implementation for an unordered container is to throw an exception. The chosen
   * implementation, however, has the advantage of working for insertion-ordered containers, as
   * well.
   */
  @Override
  public List<String> order(List<String> insertionOrder) {
    return insertionOrder;
  }

   * <p>Note: This default implementation is overkill (but valid) for an unordered container. An
   * equally valid implementation for an unordered container is to throw an exception. The chosen
   * implementation, however, has the advantage of working for insertion-ordered containers, as
   * well.
   */
  @Override
  public List<Integer> order(List<Integer> insertionOrder) {
    return insertionOrder;
  }

   * <p>Note: This default implementation is overkill (but valid) for an unordered container. An
   * equally valid implementation for an unordered container is to throw an exception. The chosen
   * implementation, however, has the advantage of working for insertion-ordered containers, as
   * well.
   */
  @Override
  public List<String> order(List<String> insertionOrder) {
    return insertionOrder;
  }

   * <p>Note: This default implementation is overkill (but valid) for an unordered container. An
   * equally valid implementation for an unordered container is to throw an exception. The chosen
   * implementation, however, has the advantage of working for insertion-ordered containers, as
   * well.
   */
  @Override
  public List<Integer> order(List<Integer> insertionOrder) {
    return insertionOrder;
  }

Depending on code in this package is bad and will cause you problems with any upgrade! But the 4.x
will be particularly painful to naughty developers that import from this package! We changed a lot
to take advantage of sweet Kotlin features.

#### Credentials.basic()

The username and password parameters to `Credentials.basic()` are now non-null strings. In OkHttp
3.x, null would yield a username or password of "null".

/**
 * Adapts a [java.net.Socket] to MockWebServer's needs.
 *
 * Note that [asOkioSocket] returns a socket that closes the underlying [java.net.Socket] when both
 * of its component streams are closed. This class takes advantage of that.
 */
internal class MockWebServerSocket(
  val javaNetSocket: Socket,
) : Closeable,
  BufferedSocket {
  private val delegate = javaNetSocket.asOkioSocket()
  private val closedLatch = CountDownLatch(2)

```

</div>

Il est **FORTEMENT encouragé** que vous écriviez ou copiez le code, l'éditiez et l'exécutiez localement.

L'utiliser dans votre éditeur est ce qui vous montre vraiment les avantages de FastAPI, en voyant le peu de code que vous avez à écrire, toutes les vérifications de type, l'autocomplétion, etc.

---

## Installer FastAPI

La première étape consiste à installer FastAPI.

<div class="termy">

```console
$ python myapp.py
```

</div>

mais qui n'est pas appelé lorsqu'un autre fichier l'importe, comme dans :

```Python
from myapp import app
```

#### Pour davantage de détails

Imaginons que votre fichier s'appelle `myapp.py`.

Si vous l'exécutez avec :

<div class="termy">

```console
$ python myapp.py
```

</div>