In most cases, the same tool that is used to **run the program on startup** is also used to handle automatic **restarts**.

For example, this could be handled by:

* Docker
* Kubernetes
* Docker Compose
* Docker in Swarm Mode
* Systemd
* Supervisor
* Handled internally by a cloud provider as part of their services
* Others...

  private final EventBus eventBus;
  private final Object event;
  private final Object subscriber;
  private final Method subscriberMethod;

  /**
   * @param eventBus The {@link EventBus} that handled the event and the subscriber. Useful for
   *     broadcasting a new event based on the error.
   * @param event The event object that caused the subscriber to throw.
   * @param subscriber The source subscriber context.

In this case, the `startup` event handler function will initialize the items "database" (just a `dict`) with some values.

You can add more than one event handler function.

And your application won't start receiving requests until all the `startup` event handlers have completed.

### `shutdown` event { #shutdown-event }

 *
 * @author mbechler
 */
public interface CommonServerMessageBlockRequest extends CommonServerMessageBlock, Request {

    /**
     * Checks if the request will be handled asynchronously.
     *
     * @return request was handled asynchronously
     */
    boolean isResponseAsync();

    /**
     *
     * @return next chained message
     */
    @Override
    CommonServerMessageBlockRequest getNext();

    putEdge(N1, N2);
    assertThat(graph.predecessors(N2)).containsExactly(N1);
    // Edge direction handled correctly
    assertThat(graph.predecessors(N1)).isEmpty();
  }

  @Test
  public void successors_oneEdge() {
    putEdge(N1, N2);
    assertThat(graph.successors(N1)).containsExactly(N2);
    // Edge direction handled correctly
    assertThat(graph.successors(N2)).isEmpty();
  }

  @Test

## `Depends()`

Dependencies are handled mainly with the special function `Depends()` that takes a callable.

Here is the reference for it and its parameters.

You can import it directly from `fastapi`:

```python
from fastapi import Depends
```

::: fastapi.Depends

## `Security()`

        verifyNoInteractions(mockDir);
    }

    /**
     * Invalid/null inputs: ensure filters can handle null name and dir.
     */
    @ParameterizedTest
    @DisplayName("null and empty names are handled explicitly")
    @NullAndEmptySource
    @ValueSource(strings = { " \t\n" })
    void handlesNullAndEmptyNames(String name) throws Exception {

    }
    return makeHash();
  }

  /**
   * Computes a hash code based on the data that have been provided to this hasher. This is called
   * after all chunks are handled with {@link #process} and any leftover bytes that did not make a
   * complete chunk are handled with {@link #processRemaining}.
   */
  protected abstract HashCode makeHash();

  // Process pent-up data in chunks
  private void munchIfFull() {

```
Client #1596980209979 left the chat
```

/// tip

The app above is a minimal and simple example to demonstrate how to handle and broadcast messages to several WebSocket connections.

But keep in mind that, as everything is handled in memory, in a single list, it will only work while the process is running, and will only work with a single process.

///

## Override the default exception handlers { #override-the-default-exception-handlers }

**FastAPI** has some default exception handlers.

These handlers are in charge of returning the default JSON responses when you `raise` an `HTTPException` and when the request has invalid data.

You can override these exception handlers with your own.