python gotostate.py --failedExecutionArn '<Failed_Execution_Arn>'

def parseFailureHistory(failedExecutionArn):

    '''
    Parses the execution history of a failed state machine to get the name of failed state and the input to the failed state:
    Input failedExecutionArn = A string containing the execution ARN of a failed state machine y
    Output = A list with two elements: [name of failed state, input to failed state]
    '''
    failedAtParallelState = False
    try:
        #Get the execution history
        response = client.get\_execution\_history(
            executionArn=failedExecutionArn,
            reverseOrder=True
        )
        failedEvents = response['events']
    except Exception as ex:
        raise ex
    #Confirm that the execution actually failed, raise exception if it didn't fail.
    try:
        failedEvents[0]['executionFailedEventDetails']
    except:
        raise('Execution did not fail')
        
    '''
    If you have a 'States.Runtime' error (for example, if a task state in your state machine attempts to execute a Lambda function in a different region than the state machine), get the ID of the failed state, and use it to determine the failed state name and input.
    '''
    
    if failedEvents[0]['executionFailedEventDetails']['error'] == 'States.Runtime':
        failedId = int(filter(str.isdigit, str(failedEvents[0]['executionFailedEventDetails']['cause'].split()[13])))
        failedState = failedEvents[-1 \* failedId]['stateEnteredEventDetails']['name']
        failedInput = failedEvents[-1 \* failedId]['stateEnteredEventDetails']['input']
        return (failedState, failedInput)
        
    '''
    You need to loop through the execution history, tracing back the executed steps.
    The first state you encounter is the failed state. If you failed on a parallel state, you need the name of the parallel state rather than the name of a state within a parallel state that it failed on. This is because you can only attach goToState to the parallel state, but not a substate within the parallel state.
    This loop starts with the ID of the latest event and uses the previous event IDs to trace back the execution to the beginning (id 0). However, it returns as soon it finds the name of the failed state.
    '''

    currentEventId = failedEvents[0]['id']
    while currentEventId != 0:
        #multiply event ID by -1 for indexing because you're looking at the reversed history
        currentEvent = failedEvents[-1 \* currentEventId]
        
        '''
        You can determine if the failed state was a parallel state because it and an event with 'type'='ParallelStateFailed' appears in the execution history before the name of the failed state
        '''

        if currentEvent['type'] == 'ParallelStateFailed':
            failedAtParallelState = True

        '''
        If the failed state is not a parallel state, then the name of failed state to return is the name of the state in the first 'TaskStateEntered' event type you run into when tracing back the execution history
        '''

        if currentEvent['type'] == 'TaskStateEntered' and failedAtParallelState == False:
            failedState = currentEvent['stateEnteredEventDetails']['name']
            failedInput = currentEvent['stateEnteredEventDetails']['input']
            return (failedState, failedInput)

        '''
        If the failed state was a parallel state, then you need to trace execution back to the first event with 'type'='ParallelStateEntered', and return the name of the state
        '''

        if currentEvent['type'] == 'ParallelStateEntered' and failedAtParallelState:
            failedState = failedState = currentEvent['stateEnteredEventDetails']['name']
            failedInput = currentEvent['stateEnteredEventDetails']['input']
            return (failedState, failedInput)
        #Update the ID for the next execution of the loop
        currentEventId = currentEvent['previousEventId']
        

def attachGoToState(failedStateName, stateMachineArn):

    '''
    Given a state machine ARN and the name of a state in that state machine, create a new state machine that starts at a new choice state called 'GoToState'. "GoToState" branches to the named state, and sends the input of the state machine to that state, when a variable called "resuming" is set to True.
    Input failedStateName = A string with the name of the failed state
          stateMachineArn = A string with the ARN of the state machine
    Output response from the create_state_machine call, which is the API call that creates a new state machine
    '''

    try:
        response = client.describe\_state\_machine(
            stateMachineArn=stateMachineArn
        )
    except:
        raise('Could not get ASL definition of state machine')
    roleArn = response['roleArn']
    stateMachine = json.loads(response['definition'])
    #Create a name for the new state machine
    newName = response['name'] + '-with-GoToState'
    #Get the StartAt state for the original state machine, because you point the 'GoToState' to this state
    originalStartAt = stateMachine['StartAt']

    '''
    Create the GoToState with the variable $.resuming.
    If new state machine is executed with $.resuming = True, then the state machine skips to the failed state.
    Otherwise, it executes the state machine from the original start state.
    '''

    goToState = {'Type':'Choice', 'Choices':[{'Variable':'$.resuming', 'BooleanEquals':False, 'Next':originalStartAt}], 'Default':failedStateName}
    #Add GoToState to the set of states in the new state machine
    stateMachine['States']['GoToState'] = goToState
    #Add StartAt
    stateMachine['StartAt'] = 'GoToState'
    #Create new state machine
    try:
        response = client.create_state_machine(
            name=newName,
            definition=json.dumps(stateMachine),
            roleArn=roleArn
        )
    except:
        raise('Failed to create new state machine with GoToState')
    return response

python gotostate.py --failedExecutionArn 'arn:aws:states:us-west-2:<AWS_ACCOUNT_ID>:execution:TestMachine-with-GoToState:b2578403-f41d-a2c7-e70c-7500045288595

{
"foo": 1,
"Message": true
}

{
"foo": 1,
"Message": "Hello!",
"resuming":true
}

{
  "Comment": "An example of the Amazon States Language using a parallel state to execute two branches at the same time.",
  "StartAt": "Parallel",
  "States": {
    "Parallel": {
      "Type": "Parallel",
      "ResultPath":"$.output",
      "Next": "Parallel 2",
      "Branches": [
        {
          "StartAt": "Parallel Step 1, Process 1",
          "States": {
            "Parallel Step 1, Process 1": {
              "Type": "Task",
              "Resource": "arn:aws:lambda:us-west-2:XXXXXXXXXXXX:function:LambdaA",
              "End": true
            }
          }
        },
        {
          "StartAt": "Parallel Step 1, Process 2",
          "States": {
            "Parallel Step 1, Process 2": {
              "Type": "Task",
              "Resource": "arn:aws:lambda:us-west-2:XXXXXXXXXXXX:function:LambdaA",
              "End": true
            }
          }
        }
      ]
    },
    "Parallel 2": {
      "Type": "Parallel",
      "Next": "Final Processing",
      "Branches": [
        {
          "StartAt": "Parallel Step 2, Process 1",
          "States": {
            "Parallel Step 2, Process 1": {
              "Type": "Task",
              "Resource": "arn:aws:lambda:us-west-2:XXXXXXXXXXXXX:function:LambdaB",
              "End": true
            }
          }
        },
        {
          "StartAt": "Parallel Step 2, Process 2",
          "States": {
            "Parallel Step 2, Process 2": {
              "Type": "Task",
              "Resource": "arn:aws:lambda:us-west-2:XXXXXXXXXXXX:function:LambdaB",
              "End": true
            }
          }
        }
      ]
    },
    "Final Processing": {
      "Type": "Task",
      "Resource": "arn:aws:lambda:us-west-2:XXXXXXXXXXXX:function:LambdaC",
      "End": true
    }
  }
}

{
  "Message": "Hello!"
}

{
"output": [
    {
      "Message": "Hello!"
    },
    {
      "Message": "Hello!"
    }
  ],
}

{
   "Comment":"An example of the Amazon States Language using a parallel state to execute two branches at the same time.",
   "States":{
      "Final Processing":{
         "Resource":"arn:aws:lambda:us-west-2:XXXXXXXXXXXX:function:LambdaC",
         "End":true,
         "Type":"Task"
      },
      "GoToState":{
         "Default":"Parallel 2",
         "Type":"Choice",
         "Choices":[
            {
               "Variable":"$.resuming",
               "BooleanEquals":false,
               "Next":"Parallel"
            }
         ]
      },
      "Parallel":{
         "Branches":[
            {
               "States":{
                  "Parallel Step 1, Process 1":{
                     "Resource":"arn:aws:lambda:us-west-2:XXXXXXXXXXXX:function:LambdaA",
                     "End":true,
                     "Type":"Task"
                  }
               },
               "StartAt":"Parallel Step 1, Process 1"
            },
            {
               "States":{
                  "Parallel Step 1, Process 2":{
                     "Resource":"arn:aws:lambda:us-west-2:XXXXXXXXXXXX:LambdaA",
                     "End":true,
                     "Type":"Task"
                  }
               },
               "StartAt":"Parallel Step 1, Process 2"
            }
         ],
         "ResultPath":"$.output",
         "Type":"Parallel",
         "Next":"Parallel 2"
      },
      "Parallel 2":{
         "Branches":[
            {
               "States":{
                  "Parallel Step 2, Process 1":{
                     "Resource":"arn:aws:lambda:us-west-2:XXXXXXXXXXXX:function:LambdaB",
                     "End":true,
                     "Type":"Task"
                  }
               },
               "StartAt":"Parallel Step 2, Process 1"
            },
            {
               "States":{
                  "Parallel Step 2, Process 2":{
                     "Resource":"arn:aws:lambda:us-west-2:XXXXXXXXXXXX:function:LambdaB",
                     "End":true,
                     "Type":"Task"
                  }
               },
               "StartAt":"Parallel Step 2, Process 2"
            }
         ],
         "Type":"Parallel",
         "Next":"Final Processing"
      }
   },
   "StartAt":"GoToState"
}

{
  "foo": 1,
  "output": [
    {
      "Message": "Hello!"
    },
    {
      "Message": "Hello!"
    }
  ],
  "resuming": true
}