State Machine Will Not Accept Input Path - amazon-web-services

Question

I'm sure someone will point me to an immediate solution, but I've been at this for hours, so I'm just going to ask.
I cannot get a State Machine to accept an initial input. The intent is to set up an EventBridge trigger pointed at the State Machine with a static JSON passed to the SM to initiate with the proper parameters. In development, I'm just using Step Functions option to pass a JSON as the initial input when you select "New Execution".
This is the input:
{"event":{
"country": "countryA",
"landing_bucket": "aws-glue-countryA-inputs",
"landing_key": "countryA-Bucket/prefix/filename.csv",
"forecast_bucket": "aws-forecast-countryA",
"forecast_key": "inputs/",
"date_start": "2018-01-01",
"validation": "False",
"validation_size": 90
}
}
When looking at what is passed at the ExecutionStarted log entry:
{
"input": {
"country": "countryA",
"landing_bucket": "aws-glue-countryA-inputs",
"landing_key": "countryA-Bucket/prefix/filename.csv",
"forecast_bucket": "aws-forecast-countryA",
"forecast_key": "inputs/",
"date_start": "2018-01-01",
"validation": "False",
"validation_size": 90
}
,
"inputDetails": {
"truncated": false
},
"roleArn": "arn:aws:iam::a-valid-service-role"
}
This is the State Machine:
"Comment": "A pipeline!",
"StartAt": "Invoke Preprocessor",
"States": {
"Invoke Preprocessor": {
"Type": "Task",
"Resource": "arn:aws:states:::lambda:invoke",
"InputPath": "$.input",
"Parameters": {
"FunctionName": "arn:aws:lambda:my-lambda-arn:$LATEST"
},
"Next": "EndSM"
},
"EndSM": {
"Type": "Pass",
"Result": "Ended",
"End": true
}
}
}
I've tried nearly anything I can think of from changing the InputPath to assigning the "input" dictionary directly to a variable:
"$.event":"$.input"
To drilling down to the individual variables and assigning those directly like:
"$.country:"$.country". I've also used the new Step Functions Data Flow Simulator and can't get anywhere. If anyone has any thoughts, I'd really appreciate it.
Thanks!

Answer 1

Edited for correct solution:
You need to set the Payload.$ parameter to $. That will pass in the entire input object to the lambda.
{
"Comment": "A pipeline!",
"StartAt": "Invoke Preprocessor",
"States": {
"Invoke Preprocessor": {
"Type": "Task",
"Resource": "arn:aws:states:::lambda:invoke",
"Parameters": {
"FunctionName": "arn:aws:lambda:my-lambda-arn:$LATEST",
"Payload.$": "$"
},
"Next": "EndSM"
},
"EndSM": {
"Type": "Pass",
"Result": "Ended",
"End": true
}
}
}

Answer 2

Another thing you could do is specify the input in the parameters, this will allow you to specify only all/certain parts of the json to pass in.
{
"Comment": "A pipeline!",
"StartAt": "Invoke Preprocessor",
"States": {
"Invoke Preprocessor": {
"Type": "Task",
"Resource": "arn:aws:states:::lambda:invoke",
"InputPath": "$",
"Parameters": {
"FunctionName": "arn:aws:lambda:my-lambda-arn:$LATEST",
"input_event.$": "$.event"
},
"Next": "EndSM"
},
"EndSM": {
"Type": "Pass",
"Result": "Ended",
"End": true
}
}
}
From the code perspective you could just reference it like so (python):
input = event['input_event']