AWS SAA Study List - AutoScaling

AutoScaling

Basics

• AutoScaling increases or decreases the amount of EC2 instances based on policy
• Helps on scaling when the demand is higher or lower
• Based on 
• launch configuration which determines what to launch (AMI configuration)
• groups, which are set of EC2 instances set scale in and out based on policy
• policy what determines when to scale in and out and how much
• Can be used together with ELB health checks
• Can span multiple availability zones within region
• Uses health checks to determine the status of EC2 instance
• Sends data to CloudWatch about the ELB and EC2 instances

Limits

• Maximum amount of launch configurations is 100
• Maximum amount of AutoScaling groups is 20
• Maximum amount of scaling policies per AutoScaling group is 50

Default termination policy

• Policy can be changed if desired
• Availability Zone with most instances is selected first
• EC2 with oldest configuration is deleted first
• Instance closest to the next billing hour is deleted first
• If all of above are satisfied, instance is selected in random

Following topics are exam questions collected through Internet and should be evaluated as so. Answers are mine and have been checked with answers collected through the internet, but might still be wrong.

A user is trying to setup a scheduled scaling activity using Auto Scaling. The user wants to setup the recurring schedule. Which of the below mentioned parameters is not required in this case?
A. Maximum size
B. Auto Scaling group name
C. End time
D. Recurrence value

Why? Below is screenshot from my AutoScaling console.
 


A user has configured Auto Scaling with 3 instances. The user had created a new AMI after updating one of the instances. If the user wants to terminate two specific instances to ensure that Auto Scaling launches an instances with the new launch configuration, which command should he run?

A. as-delete-instance-in-auto-scaling-group <Instance ID> –no-decrement-desired-capacity
B. as-terminate-instance-in-auto-scaling-group <Instance ID> –update-desired-capacity
C. as-terminate-instance-in-auto-scaling-group <Instance ID> –decrement-desired-capacity
D. as-terminate-instance-in-auto-scaling-group <Instance ID> –no-decrement-desired-capacity

Why? https://docs.aws.amazon.com/cli/latest/reference/autoscaling/terminate-instance-in-auto-scaling-group.html

--should-decrement-desired-capacity | --no-should-decrement-desired-capacity (boolean)

If true , terminating the instance also decrements the size of the Auto Scaling group.

A user is planning to scale up an application by 8 AM and scale down by 7 PM daily using Auto Scaling. What should the user do in this case?

A. Setup the scaling policy to scale up and down based on the CloudWatch alarms
B. User should increase the desired capacity at 8 AM and decrease it by 7 PM manually
C. User should setup a batch process which launches the EC2 instance at a specific time
D. Setup scheduled actions to scale up or down at a specific time

Why? http://docs.aws.amazon.com/autoscaling/latest/userguide/schedule_time.html


An organization has setup Auto Scaling with ELB. Due to some manual error, one of the instances got rebooted. Thus, it failed the Auto Scaling health check. Auto Scaling has marked it for replacement. How can the system admin ensure that the instance does not get terminated?

A. Update the Auto Scaling group to ignore the instance reboot event
B. It is not possible to change the status once it is marked for replacement
C. Manually add that instance to the Auto Scaling group after reboot to avoid replacement
D. Change the health of the instance to healthy using the Auto Scaling commands

Why? http://docs.aws.amazon.com/cli/latest/reference/autoscaling/set-instance-health.html

--health-status (string)

The health status of the instance. Set to Healthy if you want the instance to remain in service. Set to Unhealthy if you want the instance to be out of service. Auto Scaling will terminate and replace the unhealthy instance.

A user has configured Auto Scaling with the minimum capacity as 2 and the desired capacity as 2. The user is trying to terminate one of the existing instance with the command: as-terminate-instance-in-auto-scaling-group<Instance ID> –decrement-desired-capacity. What will Auto Scaling do in this scenario?

A. Terminates the instance and does not launch a new instance
B. Terminates the instance and updates the desired capacity to 1
C. Terminates the instance and updates the desired capacity & minimum size to 1
D. Throws an error


An organization has configured Auto Scaling for hosting their application. The system admin wants to understand the Auto Scaling health check process. If the instance is unhealthy, Auto Scaling launches an instance and terminates the unhealthy instance. What is the order execution?

A. Auto Scaling launches a new instance first and then terminates the unhealthy instance
B. Auto Scaling performs the launch and terminate processes in a random order
C. Auto Scaling launches and terminates the instances simultaneously
D. Auto Scaling terminates the instance first and then launches a new instance

Why? http://docs.aws.amazon.com/autoscaling/latest/userguide/as-maintain-instance-levels.html#replace-unhealthy-instance "After an instance has been marked unhealthy as a result of an Amazon EC2 or Elastic Load Balancing health check, it is almost immediately scheduled for replacement. It never automatically recovers its health. You can intervene manually by calling the SetInstanceHealth action (or the as-set-instance-health command) to set the instance's health status back to healthy, but you will get an error if the instance is already terminating." "Auto Scaling creates a new scaling activity for terminating the unhealthy instance and then terminates it. Subsequently, another scaling activity launches a new instance to replace the terminated instance."


A user has configured ELB with Auto Scaling. The user suspended the Auto Scaling terminate process only for a while. What will happen to the availability zone rebalancing process (AZRebalance) during this period?

A. Auto Scaling will not launch or terminate any instances
B. Auto Scaling will allow the instances to grow more than the maximum size
C. Auto Scaling will keep launching instances till the maximum instance size
D. It is not possible to suspend the terminate process while keeping the launch active

Why? http://docs.aws.amazon.com/autoscaling/latest/userguide/as-suspend-resume-processes.html "If you suspend Launch, AZRebalance neither launches new instances nor terminates existing instances. This is because AZRebalance terminates instances only after launching the replacement instances. If you suspend Terminate, your Auto Scaling group can grow up to ten percent larger than its maximum size, because Auto Scaling allows this temporarily during rebalancing activities. If Auto Scaling cannot terminate instances, your Auto Scaling group could remain above its maximum size until you resume the Terminate process."


An organization has configured Auto Scaling with ELB. There is a memory issue in the application which is causing CPU utilization to go above 90%. The higher CPU usage triggers an event for Auto Scaling as per the scaling policy. If the user wants to find the root cause inside the application without triggering a scaling activity, how can he achieve this?

A. Stop the scaling process until research is completed
B. It is not possible to find the root cause from that instance without triggering scaling
C. Delete Auto Scaling until research is completed
D. Suspend the scaling process until research is completed

Why? http://docs.aws.amazon.com/autoscaling/latest/userguide/as-suspend-resume-processes.html "Auto Scaling enables you to suspend and then resume one or more of the Auto Scaling processes in your Auto Scaling group. This can be very useful when you want to investigate a configuration problem or other issue with your web application and then make changes to your application, without triggering the Auto Scaling process."


A user has configured ELB with Auto Scaling. The user suspended the Auto Scaling Alarm Notification (which notifies Auto Scaling for CloudWatch alarms) process for a while. What will Auto Scaling do during this period?

A. AWS will not receive the alarms from CloudWatch
B. AWS will receive the alarms but will not execute the Auto Scaling policy
C. Auto Scaling will execute the policy but it will not launch the instances until the process is resumed
D. It is not possible to suspend the AlarmNotification process

Why? http://docs.aws.amazon.com/autoscaling/latest/userguide/as-suspend-resume-processes.html
"If you suspend AlarmNotification, Auto Scaling does not automatically execute policies that would be triggered by an alarm. If you suspend Launch or Terminate, Auto Scaling would not be able to execute scale out or scale in policies, respectively."


An organization has configured two single availability zones. The Auto Scaling groups are configured in separate zones. The user wants to merge the groups such that one group spans across multiple zones. How can the user configure this?

A. Run the command as-join-auto-scaling-group to join the two groups
B. Run the command as-update-auto-scaling-group to configure one group to span across zones and delete the other group
C. Run the command as-copy-auto-scaling-group to join the two groups
D. Run the command as-merge-auto-scaling-group to merge the groups

Why? http://docs.aws.amazon.com/cli/latest/reference/autoscaling/update-auto-scaling-group.html --availability-zones (list)

One or more Availability Zones for the group.

An organization has configured Auto Scaling with ELB. One of the instance health check returns the status as Impaired to Auto Scaling. What will Auto Scaling do in this scenario?

A. Perform a health check until cool down before declaring that the instance has failed
B. Terminate the instance and launch a new instance
C. Notify the user using SNS for the failed state
D. Notify ELB to stop sending traffic to the impaired instance

Why? http://docs.aws.amazon.com/autoscaling/latest/userguide/as-maintain-instance-levels.html "If the instance status is any state other than running or if the system status is impaired, Auto Scaling considers the instance to be unhealthy and launches a replacement."


A user has setup an Auto Scaling group. The group has failed to launch a single instance for more than 24 hours. What will happen to Auto Scaling in this condition

A. Auto Scaling will keep trying to launch the instance for 72 hours
B. Auto Scaling will suspend the scaling process
C. Auto Scaling will start an instance in a separate region
D. The Auto Scaling group will be terminated automatically

Why? http://docs.aws.amazon.com/autoscaling/latest/userguide/as-suspend-resume-processes.html "Auto Scaling might suspend processes for Auto Scaling groups that repeatedly fail to launch instances. This is known as an administrative suspension, and most commonly applies to Auto Scaling groups that have been trying to launch instances for over 24 hours but have not succeeded in launching any instances. You can resume processes suspended for administrative reasons."


A user is planning to setup infrastructure on AWS for the Christmas sales. The user is planning to use Auto Scaling based on the schedule for proactive scaling. What advise would you give to the user?

A. It is good to schedule now because if the user forgets later on it will not scale up
B. The scaling should be setup only one week before Christmas
C. Wait till end of November before scheduling the activity
D. It is not advisable to use scheduled based scaling


A user is trying to setup a recurring Auto Scaling process. The user has setup one process to scale up every day at 8 am and scale down at 7 PM. The user is trying to setup another recurring process which scales up on the 1st of every month at 8 AM and scales down the same day at 7 PM. What will Auto Scaling do in this scenario

A. Auto Scaling will execute both processes but will add just one instance on the 1st
B. Auto Scaling will add two instances on the 1st of the month
C. Auto Scaling will schedule both the processes but execute only one process randomly
D. Auto Scaling will throw an error since there is a conflict in the schedule of two separate Auto Scaling Processes


A sys admin is trying to understand the Auto Scaling activities. Which of the below mentioned processes is not performed by Auto Scaling?

A. Reboot Instance
B. Schedule Actions
C. Replace Unhealthy
D. Availability Zone Re-Balancing


You have started a new job and are reviewing your company’s infrastructure on AWS. You notice one web application where they have an Elastic Load Balancer in front of web instances in an Auto Scaling Group. When you check the metrics for the ELB in CloudWatch you see four healthy instances In Availability Zone (AZ) A and zero in AZ B there are zero unhealthy instances. What do you need to fix to balance the instances across AZs?

A. Set the ELB to only be attached to another AZ
B. Make sure Auto Scaling is configured to launch in both AZs
C. Make sure your AMI is available in both AZs
D. Make sure the maximum size of the Auto Scaling Group is greater than 4


You have been asked to leverage Amazon VPC EC2 and SQS to implement an application that submits and receives millions of messages per second to a message queue. You want to ensure your application has sufficient bandwidth between your EC2 instances and SQS. Which option will provide the most scalable solution for communicating between the application and SQS?

A. Ensure the application instances are properly configured with an Elastic Load Balancer
B. Ensure the application instances are launched in private subnets with the EBS-optimized option enabled
C. Ensure the application instances are launched in public subnets with the associate-public-IP-address=trueoption enabled
D. Launch application instances in private subnets with an Auto Scaling group and Auto Scaling triggers configured to watch the SQS queue size


You have decided to change the Instance type for instances running In your application tier that are using Auto Scaling. In which area below would you change the instance type definition?

A. Auto Scaling launch configuration
B. Auto Scaling group
C. Auto Scaling policy
D. Auto Scaling tags

Why? http://docs.aws.amazon.com/autoscaling/latest/userguide/create-launch-config.html "When you create a launch configuration, you must specify information about the EC2 instances to launch, such as the Amazon Machine Image (AMI), instance type, key pair, security groups, and block device mapping."


A user is trying to delete an Auto Scaling group from CLI. Which of the below mentioned steps are to be performed by the user?

A. Terminate the instances with the ec2-terminate-instance command
B. Terminate the Auto Scaling instances with the as-terminate-instance command
C. Set the minimum size and desired capacity to 0
D. There is no need to change the capacity. Run the as-delete-group command and it will reset all values to 0


A user has created a web application with Auto Scaling. The user is regularly monitoring the application and he observed that the traffic is highest on Thursday and Friday between 8 AM to 6 PM. What is the best solution to handle scaling in this case?

A. Add a new instance manually by 8 AM Thursday and terminate the same by 6 PM Friday
B. Schedule Auto Scaling to scale up by 8 AM Thursday and scale down after 6 PM on Friday
C. Schedule a policy which may scale up every day at 8 AM and scales down by 6 PM
D. Configure a batch process to add a instance by 8 AM and remove it by Friday 6 PM


A user has configured the Auto Scaling group with the minimum capacity as 3 and the maximum capacity as 5. When the user configures the AS group, how many instances will Auto Scaling launch?

A. 3
B. 0
C. 5
D. 2


A sys admin is maintaining an application on AWS. The application is installed on EC2 and user has configured ELB and Auto Scaling. Considering future load increase, the user is planning to launch new servers proactively so that they get registered with ELB. How can the user add these instances with Auto Scaling?

A. Increase the desired capacity of the Auto Scaling group
B. Increase the maximum limit of the Auto Scaling group
C. Launch an instance manually and register it with ELB on the fly
D. Decrease the minimum limit of the Auto Scaling group



You have decided to change the instance type for instances running in your application tier that is using Auto Scaling. In which area below would you change the instance type definition?

A. Auto Scaling policy
B. Auto Scaling group
C. Auto Scaling tags
D. Auto Scaling launch configuration

Why? http://docs.aws.amazon.com/autoscaling/latest/userguide/create-launch-config.html "When you create a launch configuration, you must specify information about the EC2 instances to launch, such as the Amazon Machine Image (AMI), instance type, key pair, security groups, and block device mapping."


An Auto-Scaling group spans 3 AZs and currently has 4 running EC2 instances. When Auto Scaling needs to terminate an EC2 instance by default, AutoScaling will: Choose 2 answers

A. Allow at least five minutes for Windows/Linux shutdown scripts to complete, before terminating the instance.
B. Terminate the instance with the least active network connections. If multiple instances meet this criterion, one will be randomly selected.
C. Send an SNS notification, if configured to do so.
D. Terminate an instance in the AZ which currently has 2 running EC2 instances.
E. Randomly select one of the 3 AZs, and then terminate an instance in that AZ.

Why? http://docs.aws.amazon.com/autoscaling/latest/userguide/as-instance-termination.html#default-termination-policy "If so, it selects the Availability Zone with the most instances and at least one instance that is not protected from scale in."