AWS Step Function workflow is showing failed status when excuting

Question

I am following this tutorial for creating a sample workflow with AWS Step Functions and AWS Lambda. I have done everything as per the blog, but when I run it is showing failed status at the "Is Case Resolved" stage.

Screenshot: https://i.stack.imgur.com/ebmbb.png

I have done like below:

Step1: Created a role in AWS Management Console and copied the Role ARN value.

Step2: Created a new State Machine with the ASL code provided in the blog and added the Role ARN value.

Step3: Created all the 5 AWS Lambda Functions

Step4: Edited the state Machine and added the Resource value of the Lambda function.

Step5: Executed the workflow with the below code:

{
    "inputCaseID": "001"
}

My ASL code in state machine:

    {
      "Comment": "A simple AWS Step Functions state machine that automates a call center support session.",
      "StartAt": "Open Case",
      "States": {
        "Open Case": {
          "Type": "Task",
          "Resource": "arn:aws:lambda:us-east-2:AccountId:function:OpenCaseFunction",
          "Next": "Assign Case"
        }, 
        "Assign Case": {
          "Type": "Task",
          "Resource": "arn:aws:lambda:us-east-2:AccountId:function:AssignCaseFunction",
          "Next": "Work on Case"
        },
        "Work on Case": {
          "Type": "Task",
          "Resource": "arn:aws:lambda:us-east-2:AccountId:function:WorkOnCaseFunction",
          "Next": "Is Case Resolved"
        },
        "Is Case Resolved": {
            "Type" : "Choice",
            "Choices": [ 
              {
                "Variable": "$.Status",
                "NumericEquals": 1,
                "Next": "Close Case"
              },
              {
                "Variable": "$.Status",
                "NumericEquals": 0,
                "Next": "Escalate Case"
              }
          ]
        },
         "Close Case": {
          "Type": "Task",
          "Resource": "arn:aws:lambda:us-east-2:AccountId:function:CloseCaseFunction",
          "End": true
        },
        "Escalate Case": {
          "Type": "Task",
          "Resource": "arn:aws:lambda:us-east-2:AccountId:function:EscalateCaseFunction",
          "Next": "Fail"
        },
        "Fail": {
          "Type": "Fail",
          "Cause": "Engage Tier 2 Support."    }   
      }
    }

Error showing:

{
  "error": "States.Runtime",
  "cause": "An error occurred while executing the state 'Is Case Resolved' (entered at the event id #17). Invalid path '$.Status': The choice state's condition path references an invalid value."
}

OpenCaseFunction

exports.handler = (event, context, callback) => {
    // Create a support case using the input as the case ID, then return a confirmation message   
   var myCaseID = event.inputCaseID;
   var myMessage = "Case " + myCaseID + ": opened...";   
   var result = {Case: myCaseID, Message: myMessage};
   callback(null, result);    
};

AssignCaseFunction

exports.handler = (event, context, callback) => {    
    // Assign the support case and update the status message    
    var myCaseID = event.Case;    
    var myMessage = event.Message + "assigned...";    
    var result = {Case: myCaseID, Message: myMessage};
    callback(null, result);        
};

WorkOnCaseFunction

exports.handler = (event, context, callback) => {    
    // Generate a random number to determine whether the support case has been resolved, then return that value along with the updated message.
    var min = 0;
    var max = 1;    
    var myCaseStatus = Math.floor(Math.random() * (max - min + 1)) + min;
    var myCaseID = event.Case;
    var myMessage = event.Message;
    if (myCaseStatus == 1) {
        // Support case has been resolved    
        myMessage = myMessage + "resolved...";
    } else if (myCaseStatus == 0) {
        // Support case is still open
        myMessage = myMessage + "unresolved...";
    } 
    var result = {Case: myCaseID, Status : myCaseStatus, Message: myMessage};
    callback(null, result); 
};

EscalateCaseFunction

exports.handler = (event, context, callback) => {    
    // Escalate the support case 
    var myCaseID = event.Case;    
    var myCaseStatus = event.Status;    
    var myMessage = event.Message + "escalating.";    
    var result = {Case: myCaseID, Status : myCaseStatus, Message: myMessage};
    callback(null, result);
};

CloseCaseFunction

exports.handler = (event, context, callback) => { 
    // Close the support case    
    var myCaseStatus = event.Status;    
    var myCaseID = event.Case;    
    var myMessage = event.Message + "closed.";    
    var result = {Case: myCaseID, Status : myCaseStatus, Message: myMessage};
    callback(null, result);
};

What I am missing in this?

Always mask your Account ID. I am assuming this an Express Workflow, So you can share the logs of the state where it failed. Plus check the lambda named function:WorkOnCaseFunction what it is returning, because the further choice depends on the output of this function. — samtoddler
@samtoddler I have created a standard workflow and output of WorkOnCaseFunction is success. i.stack.imgur.com/7R2Wg.png Should we need an express workflow for this? — Matthew Pans
@Mathew check the ouput of the mentioned lambda, what it is?, you can check the logs of the state as well why it is cancelled. — samtoddler
@samtoddler Could you please check this screenshot, i.stack.imgur.com/W2Tel.png — Matthew Pans
@Mattew Pans as you see in the screenshot you shared the input is not correct. It should be something like in this screenshot where you have Status field inside the json. So check your function:WorkOnCaseFunction output and try to use the code provided in the guide. — samtoddler

samtoddler samtoddler · Accepted Answer · 2021-01-28T13:59:54

The named WorkOnCaseFunction is not producing correct output which should be something like below structure.

{ Case: '001', Status: 0, Message: 'hellounresolved...' }

It is consumed by the choice state which tries to fetch Status by using jsonpath $.Status.

If it is not present then it errors out and cancels the further execution of the statemachine.

For example:

Below is my state machine without DefaultState for Choice State, Either Fail or Success depending on the output produced by function:mytestfunction which can be either 0 or 1.

{
  "Comment": "An example of the Amazon States Language using a choice state.",
  "StartAt": "FirstState",
  "States": {
    "FirstState": {
      "Type": "Task",
      "Resource": "arn:aws:lambda:eu-central-1:1234567890:function:mytestfunction",
      "Next": "ChoiceState"
    },
    "ChoiceState": {
      "Type": "Choice",
      "Choices": [
        {
          "Variable": "$.Status",
          "NumericEquals": 1,
          "Next": "Success"
        },
        {
          "Variable": "$.Status",
          "NumericEquals": 0,
          "Next": "Failed"
        }
      ]
    },
    "Success": {
      "Type": "Pass",
      "Comment": "Success",
      "End": true
    },
    "Failed": {
      "Type": "Pass",
      "Comment": "Failed",
      "End": true
    }
  }
}

function:mytestfunction code

exports.handler = (event, context, callback) => {    
    // Generate a random number to determine whether the support case has been resolved, then return that value along with the updated message.
    var min = 0;
    var max = 1;    
    var myCaseStatus = Math.floor(Math.random() * (max - min + 1)) + min;
    var myCaseID = "001";
    var myMessage = "hello";
    if (myCaseStatus == 1) {
        // Support case has been resolved    
        myMessage = myMessage + "resolved...";
    } else if (myCaseStatus == 0) {
        // Support case is still open
        myMessage = myMessage + "unresolved...";
    } 
    var result = {Case: myCaseID, Status : myCaseStatus, Message: myMessage};
    console.log('result: %s', result);
    callback(null, result); 
};

I just added a log message what is being returned to stepfunction, plus just for testing I made message and case static.

That gives me the output like

Then this output from lambda is being consumed by Choice state and it tries to fetch just Status out of the following json which is produced by function:mytestfunction

{ Case: '001', Status: 0, Message: 'hellounresolved...' }

Now you can see what is going wrong with the lambda named WorkOnCaseFunction. It is not producing the output in the above format and your state machine is failing.

AWS Step Function workflow is showing failed status when excuting

2 Answers