**FastAPI** 会创建一个 `BackgroundTasks` 类型的对象并作为该参数传入。

## 创建一个任务函数 { #create-a-task-function }

创建要作为后台任务运行的函数。

它只是一个可以接收参数的标准函数。

它可以是 `async def` 或普通的 `def` 函数，**FastAPI** 知道如何正确处理。

在这种情况下，任务函数将写入一个文件（模拟发送电子邮件）。

由于写操作不使用 `async` 和 `await`，我们用普通的 `def` 定义函数：

{* ../../docs_src/background_tasks/tutorial001_py310.py hl[6:9] *}

## 添加后台任务 { #add-the-background-task }

在你的 *路径操作函数* 里，用 `.add_task()` 方法将任务函数传到 *后台任务* 对象中：

        // Test with timeout set
        execJob.timeout = 10;
        execJob.sessionId = "test-session";
        TimeoutTask task = execJob.testCreateTimeoutTask();
        assertNotNull(task);

        // Clean up timeout task
        task.cancel();
    }

    // Test createSystemProperties method
    @Test
    public void test_createSystemProperties() throws IOException {

  Lockable {
  private val key: String

  /** Non-null for client web sockets. These can be canceled. */
  internal var call: Call? = null

  /** This task processes the outgoing queues. Call [runWriter] to after enqueueing. */
  private var writerTask: Task? = null

  /** Null until this web socket is connected. Only accessed by the reader thread. */
  private var reader: WebSocketReader? = null

// custom devices will fail.
//
// `device_name` must not name an existing physical or custom device. It must
// follow the format:
//
//    /job:<name>/replica:<replica>/task:<task>/device:<type>:<device_num>
//
// If the device is successfully registered, `status` is set to TF_OK. Otherwise
// the device is not usable. In case of a bad status, `device.delete_device` is

        SourceSetContainer sourceSets = project.getExtensions().getByType(SourceSetContainer.class);
        SourceSet javaTestSourceSet = sourceSets.create(SOURCE_SET_NAME);

        // setup the javaRestTest task
        registerTestTask(project, javaTestSourceSet);

        // setup dependencies
        setupTestDependenciesDefaults(project, javaTestSourceSet);

        // setup IDE

blank_issues_enabled: false
contact_links:
  - name: Ask for help
    url: http://help.gradle.org/
    about: If you need help with Gradle or have a usage question, please reach our community instead of creating an issue.
  - name: Create an issue without template
    url: https://github.com/gradle/gradle/issues/new?template=blank

    @get:Input
    abstract val nullawayEnabled: Property<Boolean>

    // TODO(https://github.com/gradle/gradle/issues/27582): We cannot use a SetProperty<ResolvedArtifactResult> because some projects
    //  have no task dependencies and thus are non-CC serializable.
    @get:Input
    abstract val nullawayAwareDeps: Property<ArtifactCollection>

    init {

 * </p>
 * <strong>Note:</strong> This interface is part of work in progress and can be changed or removed without notice.
 */
public interface Builder {
    //
    // Be nice to whittle this down to Session, maybe add task segments to the session. The session really is
    // the place to store reactor related information.
    //
    void build(
            MavenSession session,
            ReactorContext reactorContext,

* the GitHub issue

* the performance
* the performance optimization

* the return type
* the return value

* the security
* the security scheme

* the task
* the background task
* the task function

* the template
* the template engine

* the type annotation
* the type hint

* the server worker
* the Uvicorn worker
* the Gunicorn Worker
* the worker process

  If var_name has been set as environment variable, use the preset value, else
  ask for user input. If no input is provided, the default is used.

  Args:
    environ_cp: copy of the os.environ.
    var_name: string for name of environment variable, e.g. "TF_NEED_CUDA".
    ask_for_var: string for how to ask for user input.
    var_default: default value string.

  Returns:
    string value for var_name