The switch is a conditional judgment node, decide the branch executes according to the value of [global variable](../parameter/global.md) and the expression result written by the user.
**Note** Execute expressions using javax.script.ScriptEngine.eval.
## Create
## Create Task
Click Project -> Management-Project -> Name-Workflow Definition, and click the Create Workflow button to enter the DAG editing page.
Drag from the toolbar <imgsrc="../../../../img/switch.png"width="20"/> task node to canvas to create a task.
**Note** After created a switch task, you must first configure the upstream and downstream, then configure the parameter of task branches.
## Parameter
@ -14,26 +16,42 @@ Drag from the toolbar <img src="../../../../img/switch.png" width="20"/> task n
- Descriptive information: Describe the function of the node.
- Task priority: When the number of worker threads is insufficient, execute in the order of priority from high to low, and tasks with the same priority will execute in a first-in first-out order.
- Worker grouping: Assign tasks to the machines of the worker group to execute. If `Default` is selected, randomly select a worker machine for execution.
- Environment name: The environment in Security, if not configured, it will not be used.
- Task group name: The group in Resources, if not configured, it will not be used.
- Times of failed retry attempts: The number of times the task failed to resubmit. You can select from drop-down or fill-in a number.
- Failed retry interval: The time interval for resubmitting the task after a failed task. You can select from drop-down or fill-in a number.
- Timeout alarm: Check the timeout alarm and timeout failure. When the task runs exceed the "timeout", an alarm email will send and the task execution will fail.
- Condition: You can configure multiple conditions for the switch task. When the conditions are satisfied, execute the configured branch. You can configure multiple different conditions to satisfy different businesses.
- Branch flow: The default branch flow, when all the conditions are not satisfied, execute this branch flow.
## Detail
## Task Example
This is demonstrated using one switch task and three shell tasks.
### Create a workflow
Create a new switch task, and three shell tasks downstream. The shell task is not required.
The switch task needs to be connected with the downstream task to configure the relationship before the downstream task can be selected.
Configure the conditions and default branches. If the conditions are met, the specified branch will be taken. If the conditions are not met, the default branch will be taken.
In the figure, if the value of the variable is "A", the branch taskA is executed, if the value of the variable is "B", the branch taskB is executed, and default is executed if both are not satisfied.
Here we have three tasks, the dependencies are `A -> B -> [C, D]`, and `task_a` is a shell task and `task_b` is a switch task
Conditions use global variables, please refer to [Global Parameter](../parameter/global.md).
The value of the global variable configured here is A.
- In task A, a global variable named `id` is defined through [global variable](../parameter/global.md), and the declaration method is `${setValue(id=1)}`
- Task B adds conditions and uses global variables declared upstream to achieve conditional judgment (Note: switch can get the global variables value, as long as its direct or indirect upstream have already assigned the global variables before switch acquires). We want to execute task C when `id = 1`, otherwise run task D
- Configure task C to run when the global variable `id=1`. Then edit `${id} == 1` in the condition of task B, and select `C` as branch flow
Execute and see if it works as expected. It can be seen that the specified downstream tasksA are executed as expected.
[condition](conditions.md)：[Condition](conditions.md)task mainly executes the corresponding branch based on the execution result status (success, failure) of the upstream node.
The [Switch](switch.md) task mainly executes the corresponding branch based on the value of the [global parameter](../parameter/global.md) and the judgment expression result written by the user.
chuxing
3 years ago
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