AWS Step Function where Map input comes from Execution Input

Question

I'm attempting to create an AWS step function with a Map state whose input (that is, the array to iterate over) comes from the Execution Input. A reduce example JSON step function looks like:

{
    "StartAt": "pass",
    "States": {
        "pass": {
            "Type": "Pass",
            "Next": "map-sleep"
        },
        "map-sleep": {
            "MaxConcurrency": 5,
            "InputPath": "$$.Execution.Input['data']",
            "Iterator": {
                "StartAt": "wait",
                "States": {
                    "wait": {
                        "SecondsPath": "$['length']",
                        "Type": "Wait",
                        "End": true
                    }
                }
            },
            "Type": "Map",
            "Next": "final-wait"
        },
        "final-wait": {
            "Seconds": 10,
            "Type": "Wait",
            "End": true
        }
    }
}

However, when I attempt to create this, I'm greeted by the error:

An error occurred (InvalidDefinition) when calling the CreateStateMachine operation: Invalid State Machine Definition: 'SCHEMA_VALIDATION_FAILED: Value must be a valid JSONPath. at /States/map-sleep/InputPath'

I infer from this that the InputPath is wrong, but I don't quite understand why, or what the correct way to express what I'm trying to do is. (This code was generated using the Python Step Functions SDK, and if it's helpful I can share this code, but I figured reducing it to the JSON would make it easier to consider).

Alex Gaynor Alex Gaynor · Accepted Answer · 2020-06-28T02:32:41

Well, I strongly suspect this is not the optimal answer, but it looks like by combining a Pass node using Parameters with a Map node, you can get the desired outcome:

        "map-sleep-pass": {
            "Parameters": {
                "items.$": "$$.Execution.Input['data']"
            },
            "Type": "Pass",
            "Next": "map-sleep"
        },
        "map-sleep": {
            "MaxConcurrency": 5,
            "InputPath": "$.items",
            "Iterator": {
                "StartAt": "wait",
                "States": {
                    "wait": {
                        "SecondsPath": "$['length']",
                        "Type": "Wait",
                        "End": true
                    }
                }
            },
            "Type": "Map",
            "Next": "final-wait"
        },

AWS Step Function where Map input comes from Execution Input

1 Answers