Dynamic Task

"type" : "DYNAMIC"

Introduction

Dynamic Task allows to execute one of the registered tasks dynamically at run-time. It accepts the task name to execute as taskToExecute in inputParameters.

Use Cases

Consider a scenario when we have to make the decision to execute a task dynamically, i.e., while the workflow is still running. In such cases, Dynamic Task would be useful. It is defined directly inside the workflow with type DYNAMIC.

Inputs

Following are the input parameters :

name	description
dynamicTaskNameParam	Name of the task to be called during workflow execution.

Dynamic SUBWORKFLOW

If there is a possibility that the task called is a SUBWORKFLOW, you must also add:

  "subWorkflowParam": {
       "name": "workflow_name",
       "version": <workflow version>
     },

If subWorkflowParam is present, and the DYNAMIC workflow calls a task type that is not a SUBWORKFLOW, these parameters will be ignored.

Output

During execution, the DYNAMIC task is replaced in the workflow with whatever task is called dynamically. The output during execution is whatever the output of the called task normally outputs.

Examples

Suppose in a workflow, we have to make the decision to ship the courier, but the decision is made during execution:

{
  "name": "Shipping_Flow",
  "description": "Ships smartly on the basis of Shipping info",
  "version": 1,
  "tasks": [
    {
      "name": "shipping_info",
      "taskReferenceName": "shipping_info",
      "inputParameters": {
      },
      "type": "SIMPLE"
    },
    {
      "name": "shipping_task",
      "taskReferenceName": "shipping_task",
      "inputParameters": {
        "taskToExecute": "${shipping_info.output.shipping_service}"
      },
      "type": "DYNAMIC",
      "dynamicTaskNameParam": "taskToExecute"
    }

  ],
  "restartable": true,
  "ownerEmail":"abc@example.com",
  "workflowStatusListenerEnabled": true,
  "schemaVersion": 2
}

The shipping_info task generates an output that is used to determine which task is run in the shipping_task DYNAMIC task.

The line "taskToExecute": "${shipping_info.output.shipping_service}" reads the shipping_service output from shipping_info.

In this example, there are two possible outputsship_via_fedex or ship_via_ups

Workflow Definition

Here is the workflow with the DYNAMIC task:

Workflow Execution

Now, assume a workflow execution where shipping_info outputs:

{
  "shipping_service": "ship_via_fedex"
}

The DYNAMIC task shipping_task has been replaced with ship_via_fedex:

If the output is:

{
  "shipping_service": "ship_via_ups"
}

The DYNAMIC task shipping_task has been replaced with ship_via_ups:

Common Errors

If the incorrect task name or the task that doesn't exist is provided, then the workflow fails and we get the error "Invalid task specified. Cannot find task by name in the task definitions."

If the null reference is provided in the task name, then also the workflow fails, and we get the error "Cannot map a dynamic task based on the parameter and input. Parameter= taskToExecute, input= {taskToExecute=null}"