AWS Step function - choice step - TimestampEquals matching with multiple input variables

Question

I have been trying to create a step function with a choice step that acts as a rule engine. I would like to compare a date variable (from the stale input JSON) to another date variable that I generate with a lambda function.

AWS documentation does not go into details about the Timestamp comparator functions, but I assumed that it can handle two input variables. Here is the relevant part of the code:

{
  "Variable": "$.staleInputVariable",
  "TimestampEquals": "$.generatedTimestampUsingLambda"
}

Here is the error that I am getting when trying to update(!!!) the stepFunction. I would like to highlight the fact that I don't even get to invoking the stepFunction as it fails while updating the function.

Resource handler returned message: "Invalid State Machine Definition: 'SCHEMA_VALIDATION_FAILED: String does not match RFC3339 timestamp at ..... (Service: AWSStepFunctions; Status Code: 400; Error Code: InvalidDefinition; Request ID: 97df9775-7d2d-4dd2-929b-470c8s741eaf; Proxy: null)" (RequestToken: 030aa97d-35a5-a6a5-0ac5-5698a8662bc2, HandlerErrorCode: InvalidRequest)

The stepfunction updates without the Timestamp matching, therefore, I suspect this bit of code.. Any guess?

EDIT (08.Jun.2021):

A comparison – Two fields that specify an input variable to compare, the type of comparison, and the value to compare the variable to. Choice Rules support comparison between two variables. Within a Choice Rule, the value of Variable can be compared with another value from the state input by appending Path to name of supported comparison operators. Source: AWS docs

It clearly states that two variables can be compared, but to no avail. Still trying :)

Electroballistics

Yeah, if I replace it with "TimestampEquals": "2016-03-14T01:59:00Z", it works. The string must conform with the RFC3339 profile of ISO 8601. Not taking any other format! – Powerhouse

I know that it works with static strings, but I can't have "magic strings" in this case.. I have to compare a variable to another variable. – Electroballistics

Answer 1

When I explained the problem to one of my peers, I realised that the AWS documentation mentions a Path postfix (which I confused with the $.). This Path needs to be added to the operatorName.

The following code works:

{
  "Variable": "$.staleInputVariable",
  "TimestampEqualsPath": "$.generatedTimestampUsingLambda"
}

Again, I would like to draw your attention to the "Path" word. That makes the magic!

Electroballistics

And in Workflow Studio, note that you must select Timestamp Variable not Timestamp Constant (same with Number Variable/Timestamp) – Ashwell

Answer 2

Looks like you indeed found a way around your initial challenge from the thread linked below.

Using an amazon step function, how do I write a choice operator that references current time?

However, I thought you wanted to compare $.staleInputVariable to the current timestamp and I wince to think you had to configure a lambda function (and test it!) to do only that.

If so, you could have achieved that simply by using the Context Object or $$.:

{
  "Variable": "$$.State.EnteredTime",
  "TimestampEqualsPath": "$.staleInputVariable"
}

Lamellar