Scheduled Task Invocation

Version

Application Scenario

You may want to invoke other scheduled tasks on the platform in the current scheduled task and orchestrate the invoked tasks in the current task. The Scheduled Task Invocation node can meet this requirement.

Function Introduction

Note:

The function supports visual display of parent-subtask invocation relationships. You can view which tasks invoke the scheduled task and which tasks are invoked by the scheduled task. For details, see Task Relation.

1. When a parent task is executed, the execution of a subtask is triggered. Multiple scheduled tasks can be executed in a specific order through the Scheduled Task Invocation node.

2. When a parent task invokes a subtask, parameters can be transferred to the subtask.

Note:

The invocation level of scheduled tasks cannot exceed five levels. Otherwise, an error is reported.

Task Invocation

Select another scheduled task from the drop-down list. The current task and tasks for which you do not have Management permission cannot be selected.

From V4.1.1, cyclic tasks are blocked in the drop-down list of Scheduled Task Invocation. For example, if Task A invokes Task B and Task B invokes Task C, Task C cannot invoke Task A.

From V4.2.14.1, if the parent task runs in development mode, the invoked subtask runs in development mode; if the parent task runs in production mode, the invoked subtask runs in production mode.

Parameter Transfer

From V4.2.14.1

1. If you tick Pass Parameter in Current Task to Subtask, you can transfer defined task parameters and parameters output by Parameter Assignment to subtasks and other multi-level downstream tasks.

2. In a subtask, parameters transferred from the parent task support auto-complete suggestions in SQL statements.

In a subtask, click Parameter List to view assigned parameters transferred from the parent task. (Static parameters are not displayed.) You can modify parameter debug values. (You are advised to set a parameter debug value to facilitate data previewing in the subtask).

Note:

If multiple parent tasks have parameters with the same name, only one parameter is displayed here.

3. If you drag another Scheduled Task Invocation node into the subtask:

• For task assignment parameters, the Scheduled Task Invocation node displays all assigned parameters transferred from upstream nodes in the current task and from upstream nodes of the Scheduled Task Invocation node in the current task. If multiple upstream nodes have parameters with the same name, only one parameter is displayed. During execution, parameters are transferred downstream according to their priorities.

• For static parameters, only static parameters of the current task are displayed.

Note:

If multiple parameters with the same name are transferred downstream, the parameters are overwritten based on the following priority: assignment parameters in the current task > assignment parameters in the parent task > static parameters in the parent task > static parameters in the current task.

Versions Earlier Than V4.2.14.1

This option is unticked by default. If you tick Pass Parameter in Current Task to Subtask, you can transfer defined task parameters and parameters output by Parameter Assignment to subtasks.

The setting area with this option ticked is shown in the following figure.

Assignment Parameter of Task: It displays parameters output by the upstream Parameter Assignment node of the same branch of the Invocation Task node only. Parameters output by Parameter Assignment can be used by all downstream nodes in the same branch. Cross-branch use is not supported.

Static Parameter of Task: All defined task parameters can be passed to subtasks.

Description of Cross-Level Parameter Transfer Logic

1. If the parameter is a task parameter:

You can pass only parameters defined in the current task to subtasks. Therefore, in a scenario with more than two levels, if a subtask wants to use a parameter in a grandparent task, the two upper-level tasks must both have the parameter with the same name and must both be configured to pass the parameters to subtasks.

For example, Task c is configured with the parameter p1, whose value is 1. If you want to use p1 in Task a(with a parameter value of 1), Task b must be configured with the parameter p1, whose value can be different. In both Task c and Task b, tick Pass Parameter in Current Task to Subtask.

2. If the parameter is output by the Parameter Assignment node:

Because the priority of parameters output by Parameter Assignment is higher than that of parameters from the parent task in Scheduled Task Invocation, if you want to transfer a parameter output by Parameter Assignment in a task to its sub-subtask, use the Parameter Assignment node in the subtask to obtain the parameter from the task, and then transfer it to the sub-subtask, as shown in the following figure.

Task Scheduling Conflict

Assume that both the parent task and the subtask are configured with a scheduling plan. 

If the subtask is running when you run the parent task, the subtask will be executed after the preceding execution is completed.

If multiple parent tasks invoke the same subtask, the subtask will be executed multiple times in the order of invocation. The next execution starts after the former one is completed.