Serverless Step Functions: no more leaky abstractions

I have some exciting news to share with you about the Serverless Step Functions plugin.

One of the main pain points of using the plugin was that you needed to use fully-formed ARNs. We addressed this in v1.18.0 by supporting CloudFormation intrinsic functions Fn:GetAtt and Ref. This makes it possible for you to reference a local function instead.

functions:
  hello-world:
    handler: hello-world.handler

stepFunctions:
  stateMachines:
    myStateMachine:
      definition:
        StartAt: HelloWorld
        States:
          HelloWorld:
            Type: Task
            Resource:
              Fn::GetAtt: [HelloDashworldLambdaFunction, Arn]
            End: true

But this is still a leaky abstraction – you have to know how the Serverless framework converts local function names into CloudFormation logical IDs.

Newcomers would often get confused here.

“How did you get the logical ID HelloDashworldLambdaFunction from hello-world?”

I can hardly blame them for not knowing. This is an implementation detail in the Serverless framework, one that you shouldn’t have to care about!

Which is why I’m really happy to tell you that, as of v2.2.0 you can reference local functions using their local names in the state machine definition.

In the above example, when we reference the local function hello-world we no longer need to use its CloudFormation logical ID HelloDashworldLambdaFunction.

As you can see from the example, it applies when you use either Ref or Fn::GetAtt functions in a Task state. And it applies to all 3 ways of invoking a Lambda function from a Task state.

Liked this article? Support me on Patreon and get direct help from me via a private Slack channel or 1-2-1 mentoring.
Subscribe to my newsletter


Hi, I’m Yan. I’m an AWS Serverless Hero and the author of Production-Ready Serverless.

I specialise in rapidly transitioning teams to serverless and building production-ready services on AWS.

Are you struggling with serverless or need guidance on best practices? Do you want someone to review your architecture and help you avoid costly mistakes down the line? Whatever the case, I’m here to help.

Hire me.


Check out my new course, Complete Guide to AWS Step Functions. In this course, we’ll cover everything you need to know to use AWS Step Functions service effectively. Including basic concepts, HTTP and event triggers, activities, callbacks, nested workflows, design patterns and best practices.

Get Your Copy


Come learn about operational BEST PRACTICES for AWS Lambda: CI/CD, testing & debugging functions locally, logging, monitoring, distributed tracing, canary deployments, config management, authentication & authorization, VPC, security, error handling, and more.

You can also get 40% off the face price with the code ytcui.

Get Your Copy