DOP-C02 · Question #172
A DevOps engineer notices that all Amazon EC2 instances running behind an Application Load Balancer in an Auto Scaling group are failing to respond to user requests. The EC2 instances are also failing
The correct answer is A. Change the Auto Scaling configuration to replace the instances when they fail the load balancer's E. Use the Amazon CloudWatch agent to collect the memory utilization of the EC2 instances in the. To improve resilience against application memory leaks and enable proactive monitoring, configure the Auto Scaling group to replace instances that fail load balancer health checks. Simultaneously, deploy the CloudWatch agent on EC2 instances to collect memory utilization metrics
Question
A DevOps engineer notices that all Amazon EC2 instances running behind an Application Load Balancer in an Auto Scaling group are failing to respond to user requests. The EC2 instances are also failing target group HTTP health checks. Upon inspection, the engineer notices the application process was not running in any EC2 instances. There are a significant number of out of memory messages in the system logs. The engineer needs to improve the resilience of the application to cope with a potential application memory leak. Monitoring and notifications should be enabled to alert when there is an issue. Which combination of actions will meet these requirements? (Choose two.)
Options
- AChange the Auto Scaling configuration to replace the instances when they fail the load balancer's
- BChange the target group health check HealthCheckIntervalSeconds parameter to reduce the
- CChange the target group health checks from HTTP to TCP to check if the port where the
- DEnable the available memory consumption metric within the Amazon CloudWatch dashboard for
- EUse the Amazon CloudWatch agent to collect the memory utilization of the EC2 instances in the
How the community answered
(30 responses)- A67% (20)
- B3% (1)
- C10% (3)
- D20% (6)
Why each option
To improve resilience against application memory leaks and enable proactive monitoring, configure the Auto Scaling group to replace instances that fail load balancer health checks. Simultaneously, deploy the CloudWatch agent on EC2 instances to collect memory utilization metrics for early detection and alerting of potential memory leaks.
Configuring the Auto Scaling group to automatically terminate and replace instances marked unhealthy by the load balancer is a reactive resilience measure, ensuring that instances with crashed applications due to memory leaks are cycled out, thus improving application availability.
While reducing the `HealthCheckIntervalSeconds` accelerates the detection of unhealthy instances, it does not directly address the root cause (memory leak) or improve resilience beyond faster identification.
Changing health checks from HTTP to TCP only verifies port connectivity, which is less specific than an HTTP check that confirms the application's ability to serve requests and thus would not improve the detection of a failed application process.
Enabling a metric within an Amazon CloudWatch dashboard only provides visualization; it does not collect the memory utilization metric from the EC2 instances, which requires the CloudWatch agent, nor does it inherently configure alerts.
The Amazon CloudWatch agent is required to collect detailed memory utilization metrics from within the EC2 instance operating system, as these metrics are not natively published to CloudWatch. Collecting these metrics enables proactive monitoring and allows for setting up alarms to detect memory leaks before they cause a full application crash.
Concept tested: Auto Scaling health checks, CloudWatch custom metrics for EC2, application resilience
Source: https://docs.aws.amazon.com/autoscaling/ec2/userguide/as-healthchecks.html
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