Calls are executed in one of two ways:

 * **Synchronous:** your thread blocks until the response is readable.

   * become idle after the [onResponse][Callback.onResponse] or [onFailure][Callback.onFailure]
   * callback has returned. Synchronous calls become idle once [execute()][Call.execute] returns.
   * This means that if you are doing synchronous calls the network layer will not truly be idle
   * until every returned [Response] has been closed.
   */
  var idleCallback: Runnable? = null

Hier ist ein wenig über diese Geschichte.

## Alternativen

Ich habe seit mehreren Jahren APIs mit komplexen Anforderungen (maschinelles Lernen, verteilte Systeme, asynchrone Jobs, NoSQL-Datenbanken, usw.) erstellt und leitete mehrere Entwicklerteams.

Dabei musste ich viele Alternativen untersuchen, testen und nutzen.

 * when responses are of an unexpected type or cannot be decoded.
 *
 * Other exception types cancel the current call:
 *
 *  * For synchronous calls made with [Call.execute], the exception is propagated to the caller.
 *
 *  * For asynchronous calls made with [Call.enqueue], an [IOException] is propagated to the caller

# Async Tests

You have already seen how to test your **FastAPI** applications using the provided `TestClient`. Up to now, you have only seen how to write synchronous tests, without using `async` functions.

## Créer une fonction de tâche

Une fonction à exécuter comme tâche d'arrière-plan est juste une fonction standard qui peut recevoir des paramètres.

Elle peut être une fonction asynchrone (`async def`) ou une fonction normale (`def`), **FastAPI** saura la gérer correctement.

Dans cet exemple, la fonction de tâche écrira dans un fichier (afin de simuler un envoi d'email).

   */
  private static boolean isDeclaredThreadSafe(Method method) {
    return method.getAnnotation(AllowConcurrentEvents.class) != null;
  }

  /**
   * Subscriber that synchronizes invocations of a method to ensure that only one thread may enter
   * the method at a time.
   */
  @VisibleForTesting
  static final class SynchronizedSubscriber extends Subscriber {

root_access                     (boolean)   turn 'off' root credential access for all API calls including s3, admin operations (default: 'on')
sync_events                     (boolean)   set to enable synchronous bucket notifications (default: 'off')
object_max_versions             (number)    set max allowed number of versions per object (default: '9223372036854775807')
```

or environment variables

```

Replication of object version and metadata

If an object meets replication rules as set in the replication configuration, `X-Amz-Replication-Status` is first set to `PENDING` as the PUT operation completes and replication is queued (unless synchronous replication is in place). After replication is performed, the metadata on the source object version changes to `COMPLETED` or `FAILED` depending on whether replication succeeded. The object version on the target shows `X-Amz-Replication-Status`...

Voici un petit bout de cette histoire.

## Alternatives

Je crée des API avec des exigences complexes depuis plusieurs années (Machine Learning, systèmes distribués, jobs asynchrones, bases de données NoSQL, etc), en dirigeant plusieurs équipes de développeurs.

Dans ce cadre, j'ai dû étudier, tester et utiliser de nombreuses alternatives.