👀 Views: 60 💬 Answers: 1 📅 Created: 2025-06-09

aws lambda step-functions json Python

I'm stuck on something that should probably be simple... I'm converting an old project and I'm trying to orchestrate a workflow using AWS Step Functions that integrates with multiple Lambda functions. However, I'm working with a frustrating behavior: `Task failed: Invalid Output`. My state machine is supposed to call a Lambda function that returns a JSON object, but it seems that the output format is not being accepted. Here's the relevant part of my Step Function definition: ```json { "Comment": "A simple AWS Step Functions state machine that invokes a Lambda function.", "StartAt": "MyLambdaTask", "States": { "MyLambdaTask": { "Type": "Task", "Resource": "arn:aws:lambda:us-west-2:123456789012:function:MyFunction", "OutputPath": "$.Payload", "Next": "SuccessState" }, "SuccessState": { "Type": "Succeed" } } } ``` In my Lambda function, I'm returning the following response: ```python def lambda_handler(event, context): return { 'statusCode': 200, 'body': json.dumps({'result': 'success'}) } ``` I've tried simplifying the output by returning just a dictionary (without `statusCode` and `body`), but I still get the same behavior. My IAM role for the Step Function has permissions to invoke the Lambda function correctly, as verified in the AWS Management Console. Additionally, I checked the CloudWatch logs for the Lambda function, and it shows that the function executes successfully and logs the expected output. However, the behavior continues in Step Functions, and I need to figure out why. Has anyone experienced this scenario or have suggestions on how to resolve the 'Invalid Output' behavior? My team is using Python for this REST API. I appreciate any insights! I'm coming from a different tech stack and learning Python.