# Scheduling Tasks

Spring Cloud Data Flow 允许用户通过 `cron表达式`安排 Task 的执行。可以通过 RESTful API 或 Spring Cloud Data Flow UI 创建计划。

## 1. 调度程序

Spring Cloud Data Flow 将通过云平台上提供的调度代理安排 Task 的执行。使用Cloud Foundry平台时，Spring Cloud Data Flow将使用 [PCF Scheduler](https://www.cloudfoundry.org/the-foundry/scheduler/)。当使用 Kubernetes ，将使用 [cronjob](https://kubernetes.io/docs/concepts/workloads/controllers/cron-jobs/)。

![调度程序架构概述](https://raw.githubusercontent.com/spring-cloud/spring-cloud-dataflow/master/spring-cloud-dataflow-docs/src/main/asciidoc/images/dataflow-scheduling-architecture.png)

## 2. 启用计划

默认情况下，Spring Cloud Data Flow 会禁用调度功能。要启用计划功能，必须将以下属性设置为`true`：

* `spring.cloud.dataflow.features.schedules-enabled`
* `spring.cloud.dataflow.features.tasks-enabled`

## 3. Schedule的生命周期

schedule 的生命周期有两部分：

* [Scheduling a Task Execution](https://docs.spring.io/spring-cloud-dataflow/docs/2.1.0.RELEASE/reference/htmlsingle/#spring-cloud-data-flow-schedule-scheduling)
* [Deleting a Schedule](https://docs.spring.io/spring-cloud-dataflow/docs/2.1.0.RELEASE/reference/htmlsingle/#spring-cloud-data-flow-schedule-unscheduling)

### **3.1. 安排 Task 执行**

您可以通过以下方式安排 Task执行：

* RESTful API
* Spring Cloud Data Flow Dashboard

要从 UI 安排，请单击屏幕顶部的`Tasks`选项卡，这将转到 Task Definitions 页面。然后，从要安排的Task Definitions中，单击与要安排的任务定义关联的 clock 图标。这将引导您进入一个`Create Schedule(s)`页面，为计划创建唯一名称并关联的cron表达式。您可以为单个 Task Definitions 创建多个计划。

### **3.2. 删除计划**

您可以通过以下方式删除计划：

* RESTful API
* Spring Cloud Data Flow Dashboard

{% hint style="warning" %}
删除计划，并不会停止当前正在运行的任务。
{% endhint %}


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