* the "running" state need to perform a periodic task. Subclasses can implement {@link #startUp},
 * {@link #shutDown} and also a {@link #runOneIteration} method that will be executed periodically.
 *
 * <p>This class uses the {@link ScheduledExecutorService} returned from {@link #executor} to run
 * the {@link #startUp} and {@link #shutDown} methods and also uses that service to schedule the

    private final Object lock = new Object();

    /*
     * Conceptually, these two variables describe the executor being in
     * one of three states:
     *   - Active: shutdown == false
     *   - Shutdown: runningTasks > 0 and shutdown == true
     *   - Terminated: runningTasks == 0 and shutdown == true
     */
    @GuardedBy("lock")

        return
      }
    }
    throw AssertionError("No such job: $url")
  }

  override fun shutdown() {
    shutdown = true
  }

  override fun shutdownNow(): List<Runnable> {
    throw UnsupportedOperationException()
  }

  override fun isShutdown(): Boolean {
    return shutdown
  }

  override fun isTerminated(): Boolean {
    throw UnsupportedOperationException()
  }

### `shutdown` event

To add a function that should be run when the application is shutting down, declare it with the event `"shutdown"`:

```Python hl_lines="6"
{!../../../docs_src/events/tutorial002.py!}
```

Here, the `shutdown` event handler function will write a text line `"Application shutdown"` to a file `log.txt`.

!!! info

   * message buffer (16 MiB) will be rejected and trigger a [graceful shutdown][close] of this web
   * socket. This method returns false in that case, and in any other case where this web socket is
   * closing, closed, or canceled.
   *
   * This method returns immediately.
   */
  fun send(bytes: ByteString): Boolean

  /**
   * Attempts to initiate a graceful shutdown of this web socket. Any already-enqueued messages will

하나 이상의 이벤트 핸들러 함수를 추가할 수도 있습니다.

그리고 응용 프로그램은 모든 `startup` 이벤트 핸들러가 완료될 때까지 요청을 받지 않습니다.

## `shutdown` 이벤트

응용 프로그램이 종료될 때 실행하려는 함수를 추가하려면 `"shutdown"` 이벤트로 선언합니다:

```Python hl_lines="6"
{!../../../docs_src/events/tutorial002.py!}
```

이 예제에서 `shutdown` 이벤트 핸들러 함수는 `"Application shutdown"`이라는 텍스트가 적힌 `log.txt` 파일을 추가할 것입니다.

!!! info "정보"

		return srv.Server.Serve(l)
	}

	return
}

// Shutdown - shuts down HTTP server.
func (srv *Server) Shutdown() error {
	srv.listenerMutex.Lock()
	if srv.listener == nil {
		srv.listenerMutex.Unlock()
		return http.ErrServerClosed
	}
	srv.listenerMutex.Unlock()

	if atomic.AddUint32(&srv.inShutdown, 1) > 1 {
		// shutdown in progress
		return http.ErrServerClosed
	}

    task: Task,
    delayNanos: Long = 0L,
  ) {
    taskRunner.lock.withLock {
      if (shutdown) {
        if (task.cancelable) {
          taskRunner.logger.taskLog(task, this) { "schedule canceled (queue is shutdown)" }
          return
        }
        taskRunner.logger.taskLog(task, this) { "schedule failed (queue is shutdown)" }
        throw RejectedExecutionException()
      }

                  // which case we should skip right down to shutdown.
                  if (isRunning()) {
                    try {
                      AbstractExecutionThreadService.this.run();
                    } catch (Throwable t) {
                      restoreInterruptIfIsInterruptedException(t);
                      try {
                        shutDown();
                      } catch (Exception ignored) {

本例中，`startup` 事件处理器函数为项目数据库（只是**字典**）提供了一些初始值。

**FastAPI** 支持多个事件处理器函数。

只有所有 `startup` 事件处理器运行完毕，**FastAPI** 应用才开始接收请求。

## `shutdown` 事件

使用 `shutdown` 事件声明 `app` 关闭时运行的函数：

```Python hl_lines="6"
{!../../../docs_src/events/tutorial002.py!}
```

此处，`shutdown` 事件处理器函数在 `log.txt` 中写入一行文本 `Application shutdown`。

!!! info "说明"

    `open()` 函数中，`mode="a"` 指的是**追加**。因此这行文本会添加在文件已有内容之后，不会覆盖之前的内容。

!!! tip "提示"