Skip to content

README.md

Latest commit

 

History

History
184 lines (149 loc) · 5.14 KB

README.md

File metadata and controls

184 lines (149 loc) · 5.14 KB

Saga Pattern with AWS Lambda durable functions (Node.js)

This pattern demonstrates the Saga pattern for distributed transactions using AWS Lambda durable functions in Node.js. It coordinates a multi-step travel booking process (flight, hotel, car) with automatic compensating transactions on failure.

What is the Saga Pattern?

The Saga pattern manages distributed transactions by breaking them into a sequence of local transactions. Each step can succeed or fail independently, and if any step fails, compensating transactions automatically undo previously completed steps to maintain data consistency.

Architecture

This implementation uses a single Lambda durable function that:

  1. Executes reservation steps sequentially (flight → hotel → car)
  2. Tracks completed steps automatically via context.step()
  3. Implements compensating transactions in reverse order on failure
  4. Maintains state across retries without external storage

Key Features

  • Automatic Checkpointing: Each context.step() creates a checkpoint
  • Fault Tolerance: Execution resumes from last checkpoint on failure
  • Compensating Transactions: Automatic rollback in reverse order
  • No External State Store: Durable functions handle state management
  • Failure Simulation: Test different failure scenarios

How It Works

Success Flow

Reserve Flight → Reserve Hotel → Reserve Car → SUCCESS

Failure Flow (e.g., hotel fails)

Reserve Flight → Reserve Hotel (FAILS) → Cancel Flight → ROLLBACK COMPLETE

Failure Flow (e.g., car fails)

Reserve Flight → Reserve Hotel → Reserve Car (FAILS) → Cancel Hotel → Cancel Flight → ROLLBACK COMPLETE

Deployment

Prerequisites

  • AWS CLI configured
  • SAM CLI installed
  • Node.js 22.x

Deploy

sam build
sam deploy --guided

Follow the prompts:

  • Stack Name: saga-pattern-demo
  • AWS Region: Your preferred region
  • Confirm changes: Y
  • Allow SAM CLI IAM role creation: Y
  • Disable rollback: N
  • Save arguments to configuration file: Y

Testing

Success Case

aws lambda invoke \
  --function-name <FunctionName>:prod \
  --invocation-type Event \
  --payload '{"tripId":"trip-001","userId":"user-123"}' \
  --cli-binary-format raw-in-base64-out \
  response.json

Simulate Flight Failure

aws lambda invoke \
  --function-name <FunctionName>:prod \
  --invocation-type Event \
  --payload '{"tripId":"trip-002","userId":"user-123","simulateFailure":"flight"}' \
  --cli-binary-format raw-in-base64-out \
  response.json

Simulate Hotel Failure (triggers flight cancellation)

aws lambda invoke \
  --function-name <FunctionName>:prod \
  --invocation-type Event \
  --payload '{"tripId":"trip-003","userId":"user-123","simulateFailure":"hotel"}' \
  --cli-binary-format raw-in-base64-out \
  response.json

Simulate Car Failure (triggers hotel and flight cancellation)

aws lambda invoke \
  --function-name <FunctionName>:prod \
  --invocation-type Event \
  --payload '{"tripId":"trip-004","userId":"user-123","simulateFailure":"car"}' \
  --cli-binary-format raw-in-base64-out \
  response.json

Viewing Logs

sam logs --stack-name saga-pattern-demo --tail

Or view in CloudWatch Logs console.

Expected Output

Success Case

{
  "status": "SUCCESS",
  "message": "Trip booked successfully",
  "tripId": "trip-001",
  "userId": "user-123",
  "reservations": {
    "flight": {
      "reservationId": "FL-1234567890",
      "from": "SFO",
      "to": "NYC",
      "date": "2026-03-15",
      "status": "CONFIRMED"
    },
    "hotel": {
      "reservationId": "HT-1234567891",
      "name": "Grand Hotel NYC",
      "checkIn": "2026-03-15",
      "checkOut": "2026-03-18",
      "status": "CONFIRMED"
    },
    "car": {
      "reservationId": "CR-1234567892",
      "type": "SUV",
      "pickupDate": "2026-03-15",
      "returnDate": "2026-03-18",
      "status": "CONFIRMED"
    }
  }
}

Failure Case (hotel fails)

{
  "status": "FAILED",
  "message": "Trip booking failed, all reservations rolled back",
  "tripId": "trip-003",
  "userId": "user-123",
  "error": "Hotel reservation failed - no rooms available",
  "compensatedServices": ["flight"]
}

How durable functions Enable Saga Pattern

  1. State Management: context.step() automatically creates checkpoints when completing the operation
  2. Idempotency: Completed steps are executed exactly once, even on retries
  3. Compensation Tracking: completedSteps array tracks what needs rollback
  4. Automatic Recovery: Failed executions resume from last checkpoint
  5. No External Dependencies: No DynamoDB or Step Functions needed

Cleanup

sam delete --stack-name saga-pattern-demo

Learn More

© 2026 Amazon Web Services, Inc. or its affiliates. All Rights Reserved.

SPDX-License-Identifier: MIT-0