Orchestrating Workflows with AWS Step Functions and AWS SAM

#aws #lambda #programming #node

When a serverless application requires orchestration of multiple tasks—such as invoking various Lambda functions, implementing retries, or managing conditional logic—AWS Step Functions provides a robust and reliable solution.

Today, we'll integrate Step Functions into our AWS SAM project using AWS::Serverless::StateMachine.

🧱 Why Step Functions?

💡 Visual workflows
🔁 Built-in retries and error handling
🧩 Easily integrate with Lambda, DynamoDB, SQS, etc.
📉 Great observability via execution history

📦 Project Structure

Example directory layout:

.
├── template.yml
├── functions/
│   ├── taskOne.ts
│   └── taskTwo.ts

🔧 Step 1: Define Your Lambda Functions

In template.yml:

Resources:
  TaskOneFunction:
    Type: AWS::Serverless::Function
    Properties:
      Handler: functions/taskOne.handler
      Runtime: nodejs22.x

  TaskTwoFunction:
    Type: AWS::Serverless::Function
    Properties:
      Handler: functions/taskTwo.handler
      Runtime: nodejs22.x

Example taskOne.ts:

export const handler = async () => {
  console.log("Running Task One");
  return { status: "taskOne done" };
};

🔁 Step 2: Define the State Machine

In template.yml, add a new resource:

  MyStateMachine:
    Type: AWS::Serverless::StateMachine
    Properties:
      Name: MyWorkflow
      Definition:
        StartAt: TaskOne
        States:
          TaskOne:
            Type: Task
            Resource: !GetAtt TaskOneFunction.Arn
            Next: TaskTwo
          TaskTwo:
            Type: Task
            Resource: !GetAtt TaskTwoFunction.Arn
            End: true
      Role: !GetAtt StepFunctionExecutionRole.Arn

This creates a two-step workflow: TaskOne → TaskTwo.

🔐 Step 3: Add IAM Role for Step Functions

  StepFunctionExecutionRole:
    Type: AWS::IAM::Role
    Properties:
      AssumeRolePolicyDocument:
        Version: '2012-10-17'
        Statement:
          - Effect: Allow
            Principal:
              Service: states.amazonaws.com
            Action: sts:AssumeRole
      Policies:
        - PolicyName: StepFunctionInvokeLambda
          PolicyDocument:
            Version: '2012-10-17'
            Statement:
              - Effect: Allow
                Action:
                  - lambda:InvokeFunction
                Resource:
                  - !GetAtt TaskOneFunction.Arn
                  - !GetAtt TaskTwoFunction.Arn

✅ Bonus: Add Retry Logic

TaskOne:
  Type: Task
  Resource: !GetAtt TaskOneFunction.Arn
  Next: TaskTwo
  Retry:
    - ErrorEquals: ["Lambda.ServiceException", "Lambda.AWSLambdaException"]
      IntervalSeconds: 2
      MaxAttempts: 3

🧠 Conclusion

Using Step Functions with AWS SAM makes your serverless apps more modular, resilient, and observable.

Key benefits:

🪄 Clear separation of logic
🔁 Built-in retries and error handling
🧩 Easily scale up workflows

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