Manage AWS Step Functions Executions as an Integrated Service - AWS Step Functions

Manage AWS Step Functions Executions as an Integrated Service

Step Functions integrates with its own API as a service integration. This allows Step Functions to start a new execution of a state machine directly from the task state of a running execution. When building new workflows, use nested workflow executions to reduce the complexity of your main workflows and to reuse common processes.

For more information, see the following:

Supported Step Functions APIs and syntax:

The following includes a Task state that starts an execution of another state machine and waits for it to complete. 

{  
   "Type":"Task",
   "Resource":"arn:aws:states:::states:startExecution.sync:2",
   "Parameters":{  
      "Input":{
        "Comment": "Hello world!"
       },
      "StateMachineArn":"arn:aws:states:us-east-1:123456789012:stateMachine:HelloWorld",
      "Name":"ExecutionName"
   },
   "End":true
}

The following includes a Task state that starts an execution of another state machine. 

{  
   "Type":"Task",
   "Resource":"arn:aws:states:::states:startExecution",
   "Parameters":{  
      "Input":{
        "Comment": "Hello world!"
       },
      "StateMachineArn":"arn:aws:states:us-east-1:123456789012:stateMachine:HelloWorld",
      "Name":"ExecutionName"
   },
   "End":true
}

The following includes a Task state that implements the callback service integration pattern. 

{ 
   "Type":"Task",
   "Resource":"arn:aws:states:::states:startExecution.waitForTaskToken",
   "Parameters":{ 
      "Input":{
        "Comment": "Hello world!",
        "token.$": "$$.Task.Token"
       },
      "StateMachineArn":"arn:aws:states:us-east-1:123456789012:stateMachine:HelloWorld",
      "Name":"ExecutionName"
   },
   "End":true
}

To associate a nested workflow execution with the parent execution that started it, pass a specially named parameter that includes the execution ID pulled from the context object. When starting a nested execution, use a parameter named AWS_STEP_FUNCTIONS_STARTED_BY_EXECUTION_ID. Pass the execution ID by appending .$ to the parameter name, and referencing the ID in the context object with $$.Execution.Id. For more information, see Accessing the Context Object. 

{  
   "Type":"Task",
   "Resource":"arn:aws:states:::states:startExecution.sync",
   "Parameters":{  
      "Input":{
        "Comment": "Hello world!",
        "AWS_STEP_FUNCTIONS_STARTED_BY_EXECUTION_ID.$": "$$.Execution.Id"
       },
      "StateMachineArn":"arn:aws:states:us-east-1:123456789012:stateMachine:HelloWorld",
      "Name":"ExecutionName"
   },
   "End":true
}

Nested state machines return the following:

Resource Output
startExecution.sync String
startExecution.sync:2 JSON

Both will wait for the nested state machine to complete, but they return different Output formats. For example, if you create a Lambda function that returns the object { "MyKey": "MyValue" }, you would get the following responses:

For startExecution.sync:

{
   <other fields>
   "Output": "{ \"MyKey\": \"MyValue\" }" 
}

For startExecution.sync:2:

{
   <other fields> 
   "Output": {
      "MyKey": "MyValue"
   }
}

For information on how to configure IAM when using Step Functions with other AWS services, see IAM Policies for Integrated Services.