AWS Stepfunction & ApiGateway Dynamic path (path parameter)

Question

On my api I have a route with a path parameter: api.com/item/{id} I cannot generate the path directly from the stpefunction. I tried to concatenate the static part and the dynamic part using the intriseque function but I got this error: Reference path didn't start with '$' and I did not find any parameter to enter a path parameter in the doc

{
  "Comment": "Stepfunction",
  "StartAt": "Generate random ID",
  "States": {
    "Generate random ID": {
      "Type": "Task",
      "Resource": "${GetRandomFunctionArn}",
      "ResultPath": "$",
      "Next": "Get item"
    },
    "Get item": {
      "Type": "Task",
      "Resource": "arn:aws:states:::apigateway:invoke",
      "Parameters": {
        "ApiEndpoint": "${APIBaseUrl}",
        "Method": "GET",
        "RequestBody": {},
        "AuthType": "NO_AUTH",
        "Stage": "${APIStage}",
        "Path": "States.Format(${EndpointProductAvailability}/{}, $.item_id)"
      },
      "End": "True"
    }
  }
}

The stepfunctin is part of a sam application.

How to make an api call with one part which is an input variable and the rest which is generated by a previous task?

You might need to set .$ after Path: "Path.$": "States.Format(${EndpointProductAvailability}/{}, $.item_id)". — kylevoyto
– kylevoyto, Commented Feb 17, 2021 at 15:59

samtoddler · Accepted Answer · 2021-02-17 18:33:00Z

1

You path should be something like this:

As per this AWS Step Functions adds updates to ‘choice’ state, global access to context object, dynamic timeouts, result selection, and intrinsic functions to Amazon States Language

"Path.$": "States.Format('{}', $.item_id)"

the above works for me.

{
  "Parameters": {
    "foo.$": "States.Format('Hello, {} {}', $.firstName, $.lastName)"
  }
}

So as you shared your URL path is something like api.com/item/{id}

"Path.$": "States.Format('item/{}', $.item_id)"

Should also work.

The other I see is something like this, Generate random ID generates output like below:

{
 "apipath": "item/",
 "item_id": "1213"
}

"Path.$": "States.Format($.apipath, $.item_id)"

Intrinsic functions

edited Feb 17, 2021 at 18:33

answered Feb 17, 2021 at 18:23

samtoddler

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