Amazon EventBridge is a serverless event bus service that enables you to build event-driven applications by connecting various AWS services, SaaS applications, and custom applications. Two fundamental components of EventBridge are rules and targets.
**EventBridge Rules**
Rules are the filtering m…Amazon EventBridge is a serverless event bus service that enables you to build event-driven applications by connecting various AWS services, SaaS applications, and custom applications. Two fundamental components of EventBridge are rules and targets.
**EventBridge Rules**
Rules are the filtering mechanism that determines which events should be processed. Each rule contains an event pattern or schedule that defines when the rule should be triggered. Event patterns match incoming events based on their structure and content, including source, detail-type, and specific field values. You can create rules that filter events from AWS services, partner applications, or custom events from your own applications. Schedule-based rules use cron or rate expressions to trigger at specific intervals.
**EventBridge Targets**
Targets are the destinations where matched events are sent for processing. When an event matches a rule's pattern, EventBridge routes it to the configured targets. A single rule can have up to five targets, enabling fan-out patterns. Common targets include:
- AWS Lambda functions for serverless processing
- Amazon SNS topics for notifications
- Amazon SQS queues for message buffering
- Step Functions state machines for workflow orchestration
- Kinesis Data Streams for real-time data processing
- API Gateway endpoints for HTTP invocations
- Other EventBridge event buses for cross-account routing
**Key Concepts for Developers**
When configuring targets, you can transform the event payload using input transformers to modify the data structure before delivery. Each target requires appropriate IAM permissions through resource-based policies or IAM roles. EventBridge provides retry policies with configurable retry attempts and dead-letter queues for failed event deliveries.
For the AWS Developer Associate exam, understanding how to create rules with proper event patterns, configure multiple targets, implement input transformations, and handle error scenarios is essential for building robust event-driven architectures on AWS.
EventBridge Rules and Targets: Complete Guide for AWS Developer Associate Exam
Why EventBridge Rules and Targets Are Important
Amazon EventBridge is a serverless event bus service that enables you to build event-driven architectures. Understanding rules and targets is crucial because they form the core mechanism for routing events to the appropriate AWS services or custom applications. For the AWS Developer Associate exam, this topic frequently appears in questions about decoupling applications, building serverless architectures, and implementing event-driven workflows.
What Are EventBridge Rules?
EventBridge rules are the matching logic that determines which events should be processed and where they should be sent. A rule watches for specific events and routes them to one or more targets when a matching event occurs.
Key characteristics of rules: - Rules belong to a specific event bus - Each rule can have up to 5 targets - Rules can filter events using event patterns or scheduled expressions - Rules can be enabled or disabled - Rules process events in near real-time
What Are EventBridge Targets?
Targets are the AWS resources or endpoints that receive and process events when a rule is triggered. EventBridge supports over 20 AWS services as targets.
Common targets include: - Lambda functions - Step Functions state machines - SQS queues - SNS topics - Kinesis Data Streams - API Gateway endpoints - ECS tasks - CodePipeline - CloudWatch Log groups
How EventBridge Rules and Targets Work
Step 1: Event Generation Events are generated from AWS services, custom applications, or SaaS partners and sent to an event bus.
Step 2: Rule Evaluation EventBridge evaluates all rules associated with the event bus against incoming events. Rules use event patterns (JSON-based) to match specific event attributes.
Step 3: Target Invocation When an event matches a rule's pattern, EventBridge sends the event to all configured targets for that rule. Each target receives a copy of the event.
Event Pattern Matching
Event patterns define the structure of events that trigger rules. They support: - Exact matching on field values - Prefix matching using the prefix keyword - Numeric matching for ranges and comparisons - Anything-but matching to exclude specific values - Exists matching to check for field presence
Input Transformation
Before sending events to targets, you can transform the event data using: - Input Path: Extract specific fields from the event - Input Template: Create a custom payload format - Input Transformer: Combine path and template for complex transformations
You can configure an SQS queue as a DLQ for targets. Failed event deliveries are sent to the DLQ for later analysis and reprocessing.
Retry Policy
EventBridge has a built-in retry mechanism: - Maximum age of event: 24 hours (default), configurable 1 minute to 24 hours - Maximum retry attempts: 185 (default), configurable 0 to 185
Exam Tips: Answering Questions on EventBridge Rules and Targets
Tip 1: Know the Target Limit Remember that each rule can have a maximum of 5 targets. If a question asks about sending events to more than 5 destinations, consider using multiple rules or fan-out patterns with SNS.
Tip 2: Understand Event Pattern Syntax Be familiar with how to write event patterns. Questions may show you an event pattern and ask which events it would match. Pay attention to the JSON structure and matching operators.
Tip 3: Differentiate Between Event Buses Know the difference between the default event bus (AWS service events), custom event buses (your applications), and partner event buses (SaaS integrations).
Tip 4: Lambda as a Target When Lambda is a target, EventBridge invokes it asynchronously. Understand that Lambda handles its own retry logic for failed invocations in this scenario.
Tip 5: Cross-Account and Cross-Region EventBridge can send events to targets in other AWS accounts or regions. Questions may test your knowledge of resource-based policies required for cross-account access.
Tip 6: Scheduled vs Event-Driven Know when to use scheduled rules versus event-driven rules. Scheduled rules are for periodic tasks, while event-driven rules respond to specific occurrences.
Tip 7: Input Transformation Use Cases If a question mentions modifying or reformatting event data before sending to a target, think about input transformers. This is useful when targets expect specific payload formats.
Tip 8: Ordering and Delivery EventBridge provides at-least-once delivery. Events may be delivered more than once, so targets should be idempotent. There is no guaranteed ordering of events.
Tip 9: Archive and Replay EventBridge can archive events and replay them later. This is useful for testing, debugging, or reprocessing failed events.
Tip 10: IAM Permissions EventBridge needs permission to invoke targets. For Lambda, it uses resource-based policies. For other services, it uses IAM roles. Know which approach applies to different target types.