AWS Auto Scaling Health Checks

5 minutes 5 Questions

AWS Auto Scaling Health Checks is a feature that monitors and verifies the health status of instances within an Auto Scaling group. The service provides two types of health checks: EC2 and ELB. EC2 Health Checks monitor the status of the instance at the hypervisor level, while ELB Health Checks monitor the health of instances from the perspective of the Elastic Load Balancer. If an instance is marked as unhealthy, AWS Auto Scaling will automatically replace it with a new, healthy instance, ensuring the high availability and durability of your application. These checks can help you maintain a reliable and consistent workload distribution across your instances, so your application remains functional and accessible despite any failures.

Guide to AWS Auto Scaling Health Checks

AWS Auto Scaling health checks use automated processes to ensure that applications have the required number of instances functioning optimally.

Why is it important?

Auto Scaling health checks are vital because they automate the process of detecting failing instances and replacing them without human intervention. This ensures high availability and high performance of applications.

What is it?

A health check in AWS Auto Scaling is a way the service checks whether an instance is healthy or unhealthy. If the instance is deemed unhealthy, AWS automatically replaces it.

How does it work?

AWS carries out the checks by monitoring and verifying the reachability of the instances. EC2 and ELB health checks are used for this purpose. EC2 health checks concentrate on the instance itself, whereas ELB checks focus on traffic.

Exam Tips: Answering Questions on AWS Auto Scaling Health Checks

1. Understand the process: Understanding the Auto Scaling health check process can help predict its behavior and respond to questions more accurately.
2. Differentiate between EC2 and ELB checks: Knowing the difference between EC2 and ELB health checks can provide a more accurate context for questions.
3. Focus on failure procedures: Questions may focus on what happens when an instance fails a health check. Keep in mind that these instances are replaced automatically.
4. Review best practices: AWS recommends different best practices for health checks - ensure you are conversive with these scenarios.

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Question 1

An application runs on an Auto Scaling group of EC2 instances. If an instance fails the health check, the company wants to analyze the instance before it gets terminated. What should be modified?

Disable the health check Increase the health check grace period Create a lifecycle hook to pause terminating unhealthy instances Change the scaling cooldown period

Correct Answer: Create a lifecycle hook to pause terminating unhealthy instances

Creating a lifecycle hook allows the instance to be paused before termination, which lets the company analyze the issue. Increasing the health check grace period and changing the cooldown period do not pause termination. Disabling the health check, switching to EC2 health check, or enabling termination protection are not recommended for maintaining a healthy fleet of instances.

Question 2

A company has set up an application using an Auto Scaling group behind a Classic Load Balancer. They want to ensure timely replacement of unhealthy instances. What should be configured?

Enable connection draining in Auto Scaling Enable connection draining in Classic Load Balancer Decrease the load balancer's idle timeout Decrease the Auto Scaling termination delay

Correct Answer: Enable connection draining in Classic Load Balancer

Enabling connection draining in the Classic Load Balancer ensures the replacement of unhealthy instances without affecting users. Modifying other settings may disrupt the application's performance or not result in a timely replacement.

Question 3

An application running on an Auto Scaling group needs to be updated. What is the best method to update the application without disrupting the service?

Implement rolling updates with Auto Scaling groups Enable termination protection during the update Terminate and replace all instances simultaneously Disable the health check and update instances manually

Correct Answer: Implement rolling updates with Auto Scaling groups

Implementing rolling updates with Auto Scaling groups allows instances to be updated one by one, while keeping the service running with minimal disruption. Other options may result in possible downtime or issues with the application.

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