What feature allows instances to finish processing ongoing requests before being deregistered?

What feature allows instances to finish processing ongoing requests before being deregistered?

• A. Cross Zone Load Balancing
• B. Connection Draining
• C. Sticky Sessions
• D. Auto Scaling

Answer: (B)

The feature that allows instances to finish processing ongoing requests before being deregistered is connection draining. Connection draining is a functionality provided by Elastic Load Balancing that enables the load balancer to direct traffic away from an instance that is being deregistered, while still allowing in-progress requests to be completed. When connection draining is enabled, if an instance is marked for deregistration or is being taken offline for maintenance, the load balancer stops sending new requests to the instance immediately. Instead, it retains existing connections to the instance, allowing those requests to finish processing. This ensures that user experience is maintained and avoids abrupt interruptions for ongoing tasks, which is especially crucial for applications where state and session management are important. In contrast, cross-zone load balancing distributes traffic evenly across multiple instances in different availability zones but does not address the need for ongoing request completion when an instance is deregistered. Sticky sessions allow the load balancer to bind a user session to a specific instance, which is useful for maintaining user session state, but does not facilitate the graceful shutdown of ongoing processes. Auto Scaling helps manage the scaling of instances based on demand, but does not inherently manage the deregistration of instances in a way that allows ongoing requests to complete gracefully.

The feature that allows instances to finish processing ongoing requests before being deregistered is connection draining. Connection draining is a functionality provided by Elastic Load Balancing that enables the load balancer to direct traffic away from an instance that is being deregistered, while still allowing in-progress requests to be completed.

When connection draining is enabled, if an instance is marked for deregistration or is being taken offline for maintenance, the load balancer stops sending new requests to the instance immediately. Instead, it retains existing connections to the instance, allowing those requests to finish processing. This ensures that user experience is maintained and avoids abrupt interruptions for ongoing tasks, which is especially crucial for applications where state and session management are important.

In contrast, cross-zone load balancing distributes traffic evenly across multiple instances in different availability zones but does not address the need for ongoing request completion when an instance is deregistered. Sticky sessions allow the load balancer to bind a user session to a specific instance, which is useful for maintaining user session state, but does not facilitate the graceful shutdown of ongoing processes. Auto Scaling helps manage the scaling of instances based on demand, but does not inherently manage the deregistration of instances in a way that allows ongoing requests to complete gracefully.