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README.md

Step Functions Lambda (Python)

This sample demonstrates AWS Step Functions orchestrating multiple Lambda functions in a parallel workflow pattern.

Architecture

Input: {"adam": "LocalStack", "cole": "Stack"}
                    |
                    v
            +---------------+
            | Parallel State|
            +-------+-------+
                    |
         +----------+----------+
         |                     |
         v                     v
  +-------------+       +-------------+
  | Adam Lambda |       | Cole Lambda |
  | (extracts   |       | (extracts   |
  |  "adam")    |       |  "cole")    |
  +------+------+       +------+------+
         |                     |
         +----------+----------+
                    |
                    v
          +-----------------+
          | Combine Lambda  |
          | (joins results) |
          +--------+--------+
                   |
                   v
Output: "Together Adam and Cole say 'LocalStack Stack'!!"

AWS Services Used

  • AWS Step Functions: Workflow orchestration
  • AWS Lambda: Serverless compute (3 functions)
  • AWS IAM: Execution roles

What This Sample Demonstrates

  1. Parallel State: Running multiple branches concurrently
  2. Lambda Integration: Using Step Functions to invoke Lambda functions
  3. Data Flow: Passing data between states
  4. State Machine Definition: Amazon States Language (ASL)

Prerequisites

  • LocalStack Pro running
  • AWS CLI or awslocal installed
  • jq for JSON parsing

Deployment

# Deploy the sample
./scripts/deploy.sh

# Run tests
./scripts/test.sh

Testing

The test script validates:

Test Description
Lambda State All 3 functions are Active
State Machine State machine is ACTIVE
Adam Lambda Returns extracted 'adam' value
Cole Lambda Returns extracted 'cole' value
Combine Lambda Returns combined message
Execution State machine completes with SUCCEEDED
Output Final output matches expected format

Sample Execution

Input:

{"adam": "LocalStack", "cole": "Stack"}

Workflow:

  1. Parallel State receives input
  2. Adam Lambda extracts and returns: "LocalStack"
  3. Cole Lambda extracts and returns: "Stack"
  4. Combine Lambda receives ["LocalStack", "Stack"]
  5. Returns: "Together Adam and Cole say 'LocalStack Stack'!!"

Manual Testing

# Start an execution
awslocal stepfunctions start-execution \
    --state-machine-arn "$STATE_MACHINE_ARN" \
    --input '{"adam": "Hello", "cole": "World"}'

# Check execution status
awslocal stepfunctions describe-execution \
    --execution-arn "$EXECUTION_ARN"

Cleanup

Resources are automatically cleaned up when LocalStack restarts.