Task states and examples - CloudFlow - Alibaba Cloud Documentation Center

You can use Task states to call API operations of integrated services and complete complex workflows. This topic describes Task states and provides related usage examples of Task states. The usage examples can help you use Task states to call API operations of integrated services.

Overview

Task states are used to call API operations of integrated services to complete a job. You can use task states to invoke functions, API operations of Alibaba Cloud services, or third-party services over a common protocol such as HTTP or HTTPS. In the flow definition language (FDL), you can mark the current state as Task to indicate a Task state.

The following table describes the parameters involved in Task states.

Parameter	Type	Required	Description	Example
Name	string	Yes	The name of the state.	my-state-name
Description	string	No	The description of the state.	describe it here
Type	string	Yes	The type of the state.	Task
Action	string	Yes	The action that is to be executed in the current task. The action is usually the name of an API operation of the service, or the name of an action of the integrated service. The format of the value: <Service name>:<API operation name>.	FC:InvokeFunction
TaskMode	enum	No	The mode in which the task is invoked. CloudFlow provides three modes. For more information, see Service integration modes. RequestComplete WaitForCustomCallback WaitForSystemCallback	WaitForCustomCallback
InputConstructor	map[string]any	No	The input constructor.	See the InputConstructor section of the Inputs and outputs topic.
Parameters	map[string]any	No	The specifications for the parameters that are requested to invoke. The specifications correspond to the action. The values of the parameters can be constants or follow the JSONPath format.	For more information about the specifications, see Overview.
Timeout	string	No	The timeout period of the invocation. Unit: seconds. Valid values: 0 - 604800. A value of 0 indicates that the task never times out.	30
Timeout	string	No	You can use an expression to dynamically construct the parameter based on the context.	Timeout.$: $Input.timeout
Retry	map[string]any	No	The error retry policy.	See Error handling.
Catch	map[string]any	No	The error capture policy.	See Error handling.
OutputConstructor	map[string]any	No	The output constructor.	For more information, see the OutputConstructor section of the Inputs and outputs topic.
Next	string	No	The next state that is executed after the current state is complete. If the value of the End parameter is true, leave this parameter empty.	my-next-state
End	bool	No	Specifies whether the state is the terminal state of the current scope.	true

Sample requests

Invoke Function Compute

You can declare that a state is of the Task type and specify the information about the function to be invoked in the Parameters section based on the specifications for invoked Function Compute parameters. For more information about the parameter specifications, see Step 2: Configure invocation parameters. Functions can be invoked in optimized integration mode or in Alibaba Cloud OpenAPI.

Type: StateMachine
Name: MyWorkflow
SpecVersion: v1
StartAt: an example of synchronous function invocation
States:
  - Name: an example of synchronous function invocation
    Type: Task
    TaskMode: RequestComplete
    Action: FC:InvokeFunction
    Parameters:
      resourceArn: acs:fc:::functions/myFunction1/LATEST
      invocationType: Sync
      body:
        key: name
    Next: an example of asynchronous function invocation
  - Type: Task
    Name: an example of asynchronous function invocation
    Action: FC:InvokeFunction
    TaskMode: RequestComplete
    Parameters:
      invocationType: Async
      resourceArn: acs:fc:{region}:{accountID}:functions/myFunction/LATEST
      body:
        key: name
    Next: SucceededExit
  - Type: Pass
    Name: SucceededExit
    End: true

Call an API operation of an Alibaba Cloud service

Call the corresponding API operations based on the Alibaba Cloud OpenAPI specifications. The following sample code shows how to perform the ECS:DescribeInstances action.

Type: StateMachine
SpecVersion: v1
Name: MyWorkflow
StartAt: DescribeInstances
States:
  - Type: Task
    Name: DescribeInstances
    Action: ECS:DescribeInstances
    TaskMode: RequestComplete
    Parameters:
      RegionId: cn-hangzhou
      VpcId: vpc-bp11y195luy47h8****
      VSwitchId: vsw-bp1wb297ekw7xyh****
    End: true

Invoke a service that is not provided by Alibaba Cloud and configure task timeout and catch

In the following example, an HTTP service is invoked by using the WaitForCustomCallback integration mode. The timeout period of the task is 1 hour. If the task fails to complete within 1 hour, the workflow throws an error, which is caught by the rules specified in the Catch field.

Type: StateMachine
Name: MyWorkflow
SpecVersion: v1
StartAt: SubmitTask
States:
  - Type: Task
    Name: SubmitTask
    Action: HTTP:Request
    TaskMode: RequestComplete
    Timeout.$: $Input.timeout
    Parameters:
      method: POST
      url: https://*****
      body:
        taskName: fly
      headers:
        Content-Type: multipart/form-data
    Catch:
      - Errors:
          - FnF.TaskTimeout
        Description: 'Error capture rule #1'
        Next: NotifyOnTaskTimeout
        OutputConstructor:
          ErrorCode: TaskTimeout
          ErrorMessage: Task timed out.
    End: true
  - Type: Task
    Name: NotifyOnTaskTimeout
    Action: HTTP:Request
    TaskMode: RequestComplete
    Parameters:
      method: POST
      url: https://******
      body:
        taskName: fly
        errorCode.$: $Input.ErrorCode
        errorMessage.$: $Input.ErrorMessage
      headers:
        Content-Type: multipart/form-data
    End: true

The task timeout period is obtained from the execution input. Example of an execution input:

{
  "timeout": 10
}

If the task fails to complete within the specified time, a timeout error is caught. The workflow proceeds to the NotifyOnTaskTimeout node and sends a notification that the task has timed out.