A reporting application runs on Amazon EC2 instances behind an Application Load Balancer. The instances run in an Amazon EC2 Auto Scaling group across multiple Availability Zones. For complex reports, the application can take up to 15 minutes to respond to a request. A solutions architect is concerned that users will receive HTTP 5xx errors if a report request is in process during a scale-in event.
What should the solutions architect do to ensure that user requests will be completed before instances are terminated?
A Enable sticky sessions (session affinity) for the target group of the instances.
Incorrect. If an EC2 instance were removed from the target group during a scale-in process, the EC2 instance would fail (or would be unhealthy if it were checked). An Application Load Balancer would stop routing requests to that target and would choose a new healthy target.
For more information about sticky sessions, see Sticky Sessions for Your Application Load Balancer.
B Increase the instance size in the Application Load Balancer target group.
Incorrect. An increase of the instance size likely would increase the speed of processing. However, this solution does not directly ensure that instances that process a request are unaffected by scale-in actions. A more suitable solution would be to use deregistration delay.
For more information about deregistration delay, see Deregistration Delay.
C Increase the cooldown period for the Auto Scaling group to a greater amount of time than the time required for the longest running responses.
Incorrect. Amazon EC2 Auto Scaling cooldown periods help you prevent Auto Scaling groups from launching or terminating additional instances before the effects of previous activities are apparent.
For more information about cooldown periods, see Scaling Cooldowns for Amazon EC2 Auto Scaling.
D Increase the deregistration delay timeout for the target group of the instances to greater than 900 seconds.
Correct. By default, the Application Load Balancer waits 300 seconds before the completion of the deregistration process, which can help in-flight requests to the target become complete. To change the amount of time that the Application Load Balancer waits, update the deregistration delay value.
For more information about deregistration delay, see Deregistration Delay.
The following are the key concepts for Site-to-Site VPN:
VPN connection: A secure connection between your on-premises equipment and your VPCs.
VPN tunnel: An encrypted link where data can pass from the customer network to or from AWS.
Each VPN connection includes two VPN tunnels which you can simultaneously use for high availability.
Customer gateway: An AWS resource which provides information to AWS about your customer gateway device.
Customer gateway device: A physical device or software application on your side of the Site-to-Site VPN connection.