Event Contracts & Governance in AWS Serverless

Introduction

AWS EventBridge is a serverless event bus that enables you to connect applications using events. Understanding event contracts and governance is crucial for designing robust, scalable, and maintainable systems.

Key Concepts

• Event: A change in state or an occurrence in a system.
• Event Bus: A channel for transmitting events.
• Event Source: The origin of the event.
• Event Pattern: A filtering mechanism for events.
• Event Contract: A formal agreement on the structure and semantics of an event.

EventBridge Overview

AWS EventBridge allows for event-driven architectures to connect applications using events from various sources. It supports both AWS services and custom applications.

Event Contracts

An event contract defines the specific format and data structure of the events exchanged between systems. This includes:

• Schema Definition: JSON schema for validating the structure.
• Versioning: Managing changes over time.
• Documentation: Clear descriptions of each field and its purpose.

Example of an Event Contract

{
    "$schema": "http://json-schema.org/draft-07/schema#",
    "type": "object",
    "properties": {
        "eventType": {
            "type": "string"
        },
        "payload": {
            "type": "object",
            "properties": {
                "id": {
                    "type": "string"
                },
                "timestamp": {
                    "type": "string",
                    "format": "date-time"
                }
            },
            "required": ["id", "timestamp"]
        }
    },
    "required": ["eventType", "payload"]
}

Governance

Governance in EventBridge involves managing and controlling the use of events across the organization. This includes:

• Access Control: Define who can publish/subscribe to events.
• Monitoring: Track event flow and processing performance.
• Compliance: Ensure events meet regulatory standards.

Monitoring Example

import boto3

client = boto3.client('cloudwatch')

response = client.get_metric_data(
    MetricDataQueries=[
        {
            'Id': 'eventCount',
            'MetricStat': {
                'MetricName': 'EventCount',
                'Namespace': 'AWS/EventBridge',
                'Period': 300,
                'Stat': 'Sum',
            },
            'ReturnData': True,
        },
    ]
)

print(response)

Best Practices

When working with EventBridge, consider the following best practices:

• Define clear event contracts to avoid integration issues.
• Implement versioning for backward compatibility.
• Use event filtering to minimize processing overhead.
• Monitor events and set up alerts for failures.

FAQ