EDA Demo

This demo project exemplifies an Event-driven Architecture (EDA) using AWS Serverless services. The communication between the microservices is done using Amazon EventBridge with a choreographic approach.

• Order Service is implemented using two AWS Lambda Functions

  • Create Order: Receives new order from Amazon API Gateway, persist it in Amazon DynamoDB and publishes a CreateOrder event in Amazon EventBridge
  • Update Order: Triggered by any event from Payment Service, persist the new order status in Amazon DynamoDB and publish OrderCompleted or OrderCancelled event in Amazon EventBridge

• Payment Service implements a simple validation workflow using AWS StepFunctions

  • If the order amount is less than 500 it will publish the event PaymentSucceeded in EventBridge, otherwise PaymentFailed

• Notification Service is implemented using a Lambda function and Amazon SNS

  • Triggered by all events generated by Order and Payment services, it will notify the user when they occur

Note: For sake of simplicity, the architecture uses sparse events and no data replication or query is done between the services.

Reference Architecture

Requirement

• AWS Cloud Development Kit

Project Deployment

1. Download the sample project

   git clone https://github.com/tgpadua/aws-eda-demo

2. Access the created directory

   cd aws-eda-demo

3. Update the notification email in lib/aws-eda-demo-stack.js

   const EMAIL = '[email protected]'; 

4. Deploy the CDK project

   cdk deploy

5. Check your email and click in the Confirm subscription link

Create Payment Service

Create a new state machine in Step Functions named eda-demo-payment-service as in the diagram using the following state machine definition:

{
  "Comment": "Payment Service",
  "StartAt": "isFraud",
  "States": {
    "isFraud": {
      "Type": "Choice",
      "Choices": [
        {
          "Variable": "$.detail.amount",
          "NumericGreaterThan": 500,
          "Next": "Payment Failed"
        }
      ],
      "Default": "Payment Succeeded"
    },
    "Payment Failed": {
      "Type": "Pass",
      "Next": "Notify EventBus",
      "Result": {
        "status": "PaymentFailed"
      },
      "ResultPath": "$.payment"
    },
    "Payment Succeeded": {
      "Type": "Pass",
      "Next": "Notify EventBus",
      "Result": {
        "status": "PaymentSucceeded"
      },
      "ResultPath": "$.payment"
    },
    "Notify EventBus": {
      "Type": "Task",
      "Resource": "arn:aws:states:::events:putEvents",
      "Parameters": {
        "Entries": [
          {
            "Detail": {
              "id.$": "$.detail.id"
            },
            "DetailType.$": "$.payment.status",
            "EventBusName": "eda-demo",
            "Source": "payment-service"
          }
        ]
      },
      "End": true
    }
  }
}

Configure EventBridge

Create a bus named eda-demo with the following rules:

CloudWatch Rule

Rule name: cw-catch-all

Event Pattern:

{
  "source": [ { "exists": true } ]
}

Target: CloudWatch log group - eda-demo-all

---

Payment Service Rule

Rule name: payment-service-filtering-orders

Event Pattern:

{
  "source": ["order-service"],
  "detail-type": ["OrderCreated"]
}

Target: Step Functions state machine - eda-demo-payment-service

---

Order Service

Rule name: order-service-filtering-payments

{
  "source": ["payment-service"]
}

Target: Lambda Function - eda-demo-update-order

---

Notification Service

Rule name: notification-service

{
  "source": ["order-service","payment-service"]
}

Target: Lambda Function - eda-demo-notification

Testing

1. Set API Gateway endpoint as an environment variable

   export API=<api_gateway_endpoint>

2. Create a new order

   curl -X POST $API/order -d '{"id":101,"amount":100}'

3. Validate the test

   • Check the Step Functions execution
   • Check the DynamoDB items
   • Check the CloudWatch log group targeted by catch all EventBridge rule
   • Check your emails for notifications sent by SNS

4. Repeat the steps 2 & 3 using a different order id and amount over 500

Cleanup

cdk destroy

Appendix

Sample EventBridge Event

Order Created

{
    "version": "0",
    "id": "0be79de6-6927-ad2d-052b-f45d95ea644c",
    "detail-type": "OrderCreated",
    "source": "order-service",
    "account": "000000000000",
    "time": "2023-05-11T01:38:00Z",
    "region": "us-west-1",
    "resources": [],
    "detail": {
        "id": 101,
        "amount": 100
    }
}