Feature request: Support synchronous StepFunctions executions from API Gateway

[ljacobsson]

Describe your idea/feature/enhancement

I feel that there's a lot of improvements around the DX when creating an API Gateway -> StepFunctions Express sync integration. When working with a Lambda the DX is great, but with StepFunctions we have to dive in to writing OpenAPI spec to map the state machine output to the response.

Proposal

I wish the SAM translator could do something like this

MyExpressStateMachine:
  Type: AWS::Serverless::StateMachine
  Properties:
     ...
     Events:
       ApiEvent:
         Type: Api:
           Properties:
             Path: /{id}
             Method: get
             InvocationType: synchronous

The output from the statemachine should be mapped to the response body from API Gateway.

[GavinZZ]

Hi, thanks for opening a feature request. Will label this issue so that the team can have a discussion about adding support for for synchronous StepFunctions execution from API Gateway.

[ssenchenko]

Apologies for keeping your request without an answer for a long time.

API GW will timeout after 30sec, which means a very limited ability to benefit from a sync step-function invocation. It might lead to a frustrating UX. For that reason, async invocation of long-time running jobs from API is not a recommended pattern. Usually an async call to trigger a job execution is followed by another API call(s), from the client, which polls the status of the job.

Another possible option would be to use GraphQL Subscription to get notified when the job is done. AWS AppSync provides a serverless GraphQL service. There is also a SAM abstraction for GraphQL which simplifies the use of CloudFormation AppSync resources in IaC.

Can you please confirm if you are interested specifically in calling under 30sec sync jobs from API GW?