AWS Step Function - ResultPath not working with AWS lambda

Question

I'm trying to store the output of lambda function using ResultPath in input so that I can use that as a input in other states of step function but the step function cancelled within in few sec after adding ResultPath.

Lambda Function :

def lambda_handler(event, context):
    # TODO implement
    import boto3

    s3 = boto3.client('s3')
    data = s3.get_object(Bucket='test1', Key='Testing-sandbox/Test_sql_script.sql')
    contents = data['Body'].read()
    print(contents)
    return contents

Lambda function output :

Response
"/* Step - 1  */ \r\nSELECT * FROM test1 LIMIT 10;\r\n/* Step - 2  */ \r\nSELECT * FROM test2 limit 10;\r\n"

Step Function :

{
  "StartAt": "CallFunction",
  "States": {
    "CallFunction": {
      "Type": "Task",
      "Resource": "arn:aws:lambda:us-west-2:12345678:function:readFile",
      "ResultPath": "$.query",
      "End": true
    }
  }
}

I'm relatively new to AWS and unable debug the issue. Can someone explain this/direct me to the right documentation?

Any help/links are highly appreciated.

Vibha · Accepted Answer · 2021-05-06 03:49:19Z

1

I found the issue. It was due to the data type mismatch. The return object 'contents' is not in json format due to which it fails when step function tries to store it's output in ResultPath. Below code works for me:


   s3 = boto3.resource('s3')

    content_object = s3.Object('test1', 'Testing-sandbox/Test_sql_script.sql')
    file_content = content_object.get()['Body'].read().decode('utf-8')
    print(file_content)
    file_content2 = str(file_content).replace('\n', ' ').replace('\r', ' ')
    print(file_content2)
    print(type(file_content2))
    qr = json.dumps(file_content2)
    print(qr)

    return qr

answered May 6, 2021 at 3:49

Vibha

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