AWS Step function string/json concatenation

Question

I have orchestrated a data pipe line using AWS Step function. In last state I want to send a custom notification. I'm using an Intrinsic function States.Format to format my message and subject. It works fine for Context object element. Here, I have tested that in Message parameter. But it doesn't work with input JSON. This is my input JSON { "job-param":{ "pipe-line-name":"My pipe line name", "other-keys":"other values" } }

 "Success State": {
  "Type": "Task",     
  "Resource": "arn:aws:states:::sns:publish",
  "Parameters": {    

  "Message.$": "States.Format('Execution Id:{}, completed successfully!', $$.Execution.Id)",
  "Subject.$": "States.Format('[INFO] {} completed successfully!', $.job-param.pipe-line-name)",

  "TopicArn": "arn:aws:sns:us-east-1:************:sns-topic"
  },
  "End": true
}

While saving this state machine, it gives me following error message:

The value for the field 'Subject.$' must be a valid JSON Path

I checked Input and Result path. They have this value. I can directly use this value as parameter. This is working fine. But I can't format with other string.

"Subject.$": "$.job-param.pipe-line-name"

Alternate approach would be to call lambda to customize and trigger SNS. But I want to avoid that.

Can I request some suggestions to fix this error?

Thanks in advance!

Change your input JSON and replace - with _: ``` "Subject.$": "States.Format('[INFO] {} completed successfully!', $.job_param.pipe_line_name)", ``` — Pooya Paridel
– Pooya Paridel, Commented Nov 2, 2020 at 6:41

Pooya Paridel · Accepted Answer · 2020-11-02 23:41:15Z

7

If you want to use any name with - in your JSON then you can write your JSON Path like this:

"Subject.$": "States.Format('[INFO] {} completed successfully!', $['job-param']['pipe-line-name'])",

But it would be easier if you change your input JSON and replace - with _:

"Subject.$": "States.Format('[INFO] {} completed successfully!', $.job_param.pipe_line_name)",

answered Nov 2, 2020 at 23:41

Pooya Paridel

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1 Comment

Thinkpad Over a year ago

Thanks Poorya, converting - to _ was not possible as in my case. But $['job-param']['pipe-line-name'] worked as expected.

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