Target Group

💡 Definition

A Target Group is a logical grouping of targets (such as EC2 instances, Lambda functions, or IP addresses) that an Elastic Load Balancer routes traffic to.

🔑 Key Concepts

• Destination: It tells the load balancer where to send traffic.
• Protocol & Port: You define the protocol (e.g., HTTP) and port (e.g., 80) for the traffic sent to the targets.
• Health Checks: You define the health check settings (path, timeout, interval). The load balancer runs these checks on the Target Group to determine which targets are healthy.
• Registration: Targets (like instances) are registered with the Target Group. Auto Scaling Groups can automatically register new instances with a Target Group.

⚙️ How it Works

1. Create: Create a Target Group specifying Protocol (HTTP), Port (80), and VPC.
2. Define Health Check: e.g., "Ping /health every 30 seconds".
3. Associate: Associate the Target Group with a Listener Rule on an Application Load Balancer.
4. Register: Register instances (manually or via ASG).

🎯 Use Cases

• Routing: Sending API traffic to an "API Target Group" and web traffic to a "Web Target Group".
• Blue/Green Deployment: creating a new Target Group for the new version of your app and shifting traffic to it.

💰 Pricing Model

• There is no additional charge for Target Groups; they are a configuration component of the Load Balancer service.

📝 Exam Tips (CLF-C02)

• Used by Application Load Balancers and Network Load Balancers.
• This is where Health Checks are configured.
• It's the "glue" between the Load Balancer and the backend instances.

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See Also: * Application Load Balancer * Load Balancer * Auto Scaling