AWS step function: chosing a Resource dynamically

Question

I would like to dynamically chose an AWS Lambda worker based on the result coming from a previous step. Something like {"Resource": "$.worker_arn"}.

"RunWorkers": {
      "Type": "Map",
      "MaxConcurrency": 0,
      "InputPath": "$.output",
      "ResultPath": "$.raw_result",
      "Iterator": {
        "StartAt": "CallWorkerLambda",
        "States": {
          "CallWorkerLambda": {
            "Type": "Task",
            "Resource": "$$.worker_arn",
            "End": true
          }
        }
      },
      "Next": "Aggregate"
    },

The input from previous step is expected as following: [{"worker_arn":..., "output":1}, {"worker_arn":..., "output":1}, ...], where worker_arn is the same among all workers.

When I write a pipeline like this, the linter complains that it expects an ARN.

Are there any options better than wrapping my worker lambda into another lambda?

Answer 1

Using "Resource": "arm:aws:states:::lambda:invoke" you can set the "FunctionName" field in "Parameters" at runtime using a Path.

{ 
  "StartAt":"CallLambda", 
  "States":{ 
    "CallLambda":{ 
      "Type":"Task",    
      "Resource": "arn:aws:states:::lambda:invoke", 
      "Parameters":{ 
        "FunctionName.$":"$.MyFunction",
        "Payload.$": "$"
       }, 
      "End":true 
    } 
  } 
}

https://docs.aws.amazon.com/step-functions/latest/dg/connect-lambda.html