03. Amazon CloudWatch Events Or Amazon EventBridge

CloudWatch Events evolved into EventBridge — the serverless event bus for AWS, SaaS, and custom applications.

• Amazon CloudWatch Events was the original AWS service for reacting to AWS system changes and scheduling tasks.
• Amazon EventBridge is the next-generation version — a serverless event bus that connects AWS services, SaaS applications, and custom apps.
• Fully backward-compatible: existing CloudWatch Events rules and configurations continue to work in EventBridge.

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What is an Event Bus?

An Event Bus is the core component of Amazon EventBridge.
It acts as a central pipeline that receives, filters, and routes events between producers (event sources) and consumers (targets).

🔹 Concept

Think of an Event Bus as a post office for events —
AWS services, SaaS apps, or your own applications send events to it,
and EventBridge routes those events to the right targets (e.g., Lambda, SQS, SNS, Step Functions).

🔹 How It Works

Event Source → Event Bus → Rule → Target

Step	Description
Event Source	AWS service, SaaS app, or your custom app emitting events.
Event Bus	Channel that receives and routes events.
Rule	Filters and matches events using patterns.
Target	Processes matched events (Lambda, SNS, SQS, etc.).

🔹 Types of Event Buses

Type	Description
Default Event Bus	Automatically receives AWS service events (similar to CloudWatch Events).
Partner Event Bus	Receives events from external SaaS providers (e.g., Zendesk, Datadog, Auth0).
Custom Event Bus	Created by you for custom application or microservice events.

🧠 Example

• Your app emits an OrderPlaced event.
• The Custom Event Bus receives it.
• A Rule detects detailType = "OrderPlaced".
• The Target (Lambda) runs the order fulfillment workflow.

CloudWatch Events

• Delivers system events about changes in AWS resources.
• Example: Trigger a Lambda when an EC2 instance changes state.

Key Concepts

• Schedules (Cron jobs): Create rules that run on a schedule (e.g., hourly Lambda trigger).
• Event Patterns: React to specific AWS API/service actions (e.g., IAM root sign-in).
• Targets: Actions to trigger — Lambda, SNS, SQS, Step Functions, etc.

Amazon EventBridge

• The enhanced version of CloudWatch Events.
• Supports SaaS, custom application, and advanced event processing.

Key Features

Feature	Description
Multiple Event Buses	Default, Partner, and Custom buses to organize and route events.
Schema Registry	Auto-discovers and models event structures.
Event Archive	Stores events for compliance or debugging.
Event Replay	Reprocesses archived events.
Advanced Integrations	Connect AWS services and external systems with flexible rules.

Feature Comparison

Feature	CloudWatch Events	EventBridge
Origin	Original AWS event service	Enhanced CloudWatch Events
Event Sources	AWS only	AWS + SaaS + Custom Apps
Event Bus	Single	Multiple (Default, Partner, Custom)
Schema Registry	❌	✅
Event Archive & Replay	❌	✅
Integration Scope	AWS-only	AWS + SaaS
Use Case Breadth	AWS-centric	Full event-driven architecture

Typical Use Cases

Use Case	Example
Serverless Scheduling	Lambda every hour (cron-style)
Security Monitoring	SNS alert on IAM root sign-in
System Automation	Trigger EC2 or ECS tasks
SaaS Integration	Process Datadog/Zendesk events
Custom Applications	Handle custom business events

Exam Tip

• CloudWatch Events = old name → EventBridge = upgraded version
• EventBridge = serverless event bus for AWS, SaaS, and custom events.
• Key focus areas:
  • Event Buses (Default, Partner, Custom)
  • Rules (Patterns/Schedules)
  • Targets (Lambda, SNS, SQS, Step Functions)
  • Schema Registry, Archive, Replay

✅ All CloudWatch Events features still exist — they’re now part of Amazon EventBridge.

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🧩 02. Hands-on: Amazon EventBridge — Rules & Scheduler

Learn how to create scheduled and event-driven rules in Amazon EventBridge
using the AWS Management Console.

In this hands-on, you will:

1. Create a scheduled rule using EventBridge Scheduler to invoke a Lambda function every hour.
2. Create event pattern–based rules to:
   • Send SNS notifications when users sign in to AWS Console.
   • Notify when EC2 instances are terminated.

⚙️ Task 1: Create an Hourly Lambda Invocation (EventBridge Scheduler)

1️⃣ Open EventBridge Console

• Navigate to AWS Console → EventBridge → Create rule.

2️⃣ Create Schedule

Setting	Value
Schedule name	InvokeLambdaEveryHour
Schedule type	Recurring schedule
Expression type	Rate-based
Rate expression	rate(1 hour)

3️⃣ Configure Target

Setting	Value
Target type	AWS Lambda function
Function name	Select your Lambda (e.g., demoLambda)

• Leave Flexible time window → Off (executes exactly every hour).
• Leave retry policy and DLQ as default.

4️⃣ Permissions & Creation

• AWS creates an IAM role automatically for EventBridge Scheduler.
• Click Next → Create schedule.

✅ Result:
Your Lambda function is now automatically invoked every hour using the EventBridge Scheduler.

(EventBridge Scheduler is the new recommended way for cron/rate-based tasks.)

⚙️ Task 2: Send Notification on AWS Console Sign-in

1️⃣ Create a Rule

• EventBridge → Rules → Create rule
• Rule name: SendNotificationForLogin
• Event source: AWS events
• Event pattern type: AWS Console Sign-in events

2️⃣ Define Event Pattern

Field	Value
Service name	AWS Console Sign-in
Event type	Sign-in events

3️⃣ Add Target

Target Type	Description
SNS Topic	Choose an existing SNS topic (e.g., demo-ccp-topic).

• Click Next → Next → Create rule.

✅ Result:
Whenever a user signs into the AWS Console, an SNS notification/email is sent automatically.

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⚙️ Task 3: Detect EC2 Termination Events

1️⃣ Create a Rule

• EventBridge → Rules → Create rule
• Rule name: EC2InstanceTerminateNotification
• Event source: AWS events

2️⃣ Define Event Pattern

Field	Value
Service name	EC2
Event type	EC2 Instance State-change Notification
State filter	"state": ["terminated"]

3️⃣ Add Target

Target Type	Description
SNS Topic	Send notification to demo-ccp-topic.

• Click Next → Create rule.

✅ Result:
When any EC2 instance enters the terminated state, an SNS message is triggered.

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🧹 Clean Up

To avoid extra cost or unnecessary triggers:

• Go to EventBridge → Rules → disable or delete the created rules.
• Or, delete the InvokeLambdaEveryHour schedule.

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🧠 Key Learnings

Concept	Description
EventBridge Scheduler	Modern replacement for cron/rate rules — ideal for time-based invocations.
Event Pattern Rules	React to real-time AWS events (e.g., login, EC2 state changes).
Targets	Lambda, SNS, SQS, Step Functions, etc.
Rules vs Scheduler	Scheduler = time-based, Rule = event-based.

🧩 Summary

Rule Name	Type	Trigger	Target
InvokeLambdaEveryHour	Schedule	Every 1 hour	Lambda function
SendNotificationForLogin	Event pattern	AWS Console Sign-in	SNS Topic
EC2InstanceTerminateNotification	Event pattern	EC2 Termination	SNS Topic

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📝 Exam Tip

• EventBridge Scheduler is the new service dedicated for cron/rate expressions.
• Event Rules handle real-time AWS events.
• Always remember the flow:
  👉 Event Source → Event Bus → Rule → Target.