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Amazon web services – Merging jsons as input for AWS SFN startExeuction

I have the following aws step function step defined

"Step": {
  "Type": "Task",
  "Resource": "arn:aws:states:::states:startExecution.sync",
  "Parameters": {
    "Name.$": "$.executionName",
    "StateMachineArn": "${arn}",
    "Input.$": "$"
  }
...

I came across this documentation which illustrates how to associate workflow executions

I tried to apply this in the step above, but I keep getting an error:
InvalidDefinition: Invalid State Machine Definition: 'SCHEMA_VALIDATION_FAILED: The value for the field 'Input.$' must be a valid JSONPath or a valid intrinsic function call at ...

"Step": {
  "Type": "Task",
  "Resource": "arn:aws:states:::states:startExecution.sync",
  "Parameters": {
    "Name.$": "$.executionName",
    "StateMachineArn": "${arn}",
    "Input.$": "States.JsonMerge($, {'AWS_STEP_FUNCTIONS_STARTED_BY_EXECUTION_ID': $$.Execution.Id}, false)"
  }
...

not sure what I am doing wrong here

Tags:

2

Answers


  1. 0

    Not sure if the fist $ is meant to be previous input from a step / input that you provide upon executing the sfn, but either way.. You can construct your own json within your Input field like so:

        "Step": {
      "Type": "Task",
      "Resource": "arn:aws:states:::states:startExecution.sync",
      "Parameters": {
        "Name.$": "$.executionName",
        "StateMachineArn": "${arn}",
        "Input": {
                "PreviousInput.$": "$",
                "AWS_STEP_FUNCTIONS_STARTED_BY_EXECUTION_ID.$": "$$.Execution.Id"
           }
      }
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  2. 0

    As mentioned by @fedondev – you have to stringify and escape the object literal you are passing in second arg to JsonMerge. So your Input should look like:

    "Input.$": "States.JsonMerge($, States.StringToJson(States.Format('\{"AWS_STEP_FUNCTIONS_STARTED_BY_EXECUTION_ID":"{}"\}', $$.Execution.Id)), false)"
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