Choreography with EventBridge

1. Introduction

AWS EventBridge is a serverless event bus service that enables you to connect applications using events. Choreography is a microservices design pattern where services communicate through events, enabling scalability and flexibility.

2. Key Concepts

**Event**: A change in state or an update that is communicated to other services.
**Event Bus**: A pipeline for events to flow through; EventBridge provides a scalable event bus.
**Rules**: Define routing logic for events, determining which events trigger which targets.
**Targets**: Services that react to events, such as AWS Lambda, SNS, SQS, etc.

3. Step-by-Step Guide

3.1 Create an EventBridge Event Bus

aws events create-event-bus --name MyEventBus

3.2 Create a Rule

Specify when to trigger the rule based on event patterns.

aws events put-rule --name MyRule --event-pattern '{"source": ["my.application"]}' --event-bus-name MyEventBus

3.3 Add Targets to the Rule

Add an AWS Lambda function as a target for the rule.

aws events put-targets --rule MyRule --event-bus-name MyEventBus --targets '[{"Id": "1","Arn": "arn:aws:lambda:us-east-1:123456789012:function:MyFunction"}]'

3.4 Publish Events

aws events put-events --entries '[{"Source": "my.application","DetailType": "appRequest","Detail": "{\"key1\":\"value1\"}","EventBusName": "MyEventBus"}]'

3.5 Monitor and Debug

Use CloudWatch to monitor the events and Lambda logs to debug issues.

4. Best Practices

Use detailed event schemas to ensure clarity in your event structure.
Implement error handling in your targets to manage failures gracefully.
Adopt a naming convention for your events and rules for better organization.
Use CloudWatch Alarms to monitor your EventBridge metrics.
Limit the number of events to avoid overwhelming your event consumers.

5. FAQ

What is the difference between EventBridge and SNS?

EventBridge is designed for event-driven architectures, allowing more complex routing and filtering, while SNS is a simple notification service primarily for pub-sub messaging.

Can I use EventBridge with on-premises applications?

Yes, you can send events from on-premises applications to EventBridge via the AWS CLI or SDKs.

How does EventBridge handle event retries?

EventBridge automatically retries failed events based on the target configuration, including Lambda, which has its own retry mechanisms.

6. Workflow Flowchart


    graph TD;
        A[Start] --> B{Event Triggered}
        B -->|Yes| C[Publish Event]
        C --> D{Event Matches Rule?}
        D -->|Yes| E[Invoke Target]
        D -->|No| F[End]
        E --> G[Process Event]
        G --> H[End]