Auto Scaling and Load Balancers Flashcards
There is an application that consists of EC2 Instances behind a classic ELB. An EC2 proxy is used for content management of the backend instances. The application might not be able to scale properly.
What should be used to scale the proxy and backend instances appropriately?
Use Auto Scaling for proxy servers and backend instances
What is Cross Zone load balancing?
It allows to distribute the traffic equally between all the instances. If disabled, the traffic is instead distributed equally between the AZs regardless of how many instances each AZ contains
A solutions architect has created a new Application Load Balancer and has configured a target group with IP address as a target type.
Which of the following types of IP addresses is allowed as a valid value for this target type?
- Public IP
- Dynamic IP
- Private IP
- Elastic IP
Private IP
What is Fx Lustre?
Amazon FSx for Lustre makes it easy and cost-effective to launch and run the world’s most popular high-performance file system. It is used for workloads such as machine learning, high-performance computing (HPC), video processing, and financial modeling. The open-source Lustre file system is designed for applications that require fast storage – where you want your storage to keep up with your compute. FSx for Lustre integrates with Amazon S3, making it easy to process data sets with the Lustre file system. When linked to an S3 bucket, an FSx for Lustre file system transparently presents S3 objects as files and allows you to write changed data back to S3.
FSx for Lustre provides the ability to both process the ‘hot data’ in a parallel and distributed fashion as well as easily store the ‘cold data’ on Amazon S3. Therefore this option is the BEST fit for the given problem statement.
Can you enable content based routing on ELB?
Only on ALB, not on NLB. You can configure an Application Load Balancer to route traffic to different target groups based on the path of the url
What’s the difference between ASG Simple Policy and Step Policy?
Both are triggered by CloudWatch alarms.
With step policy, the scaling adjustment vary based on the size of the alarms.
With simple policy, this is not possible. The ASG has to wait for the new instance to be initialized and the cooldown period to end before it can be triggered again.
What’s ASG Target Policy?
You can set metrics as a target for scaling. For example, use Average CPU as a metric
A developer has created a new Application Load Balancer but has not registered any targets with the target groups. Which of the following errors would be generated by the Load Balancer?
HTTP 503: Service unavailable
What’s the difference between Launch Template and Launch Configuration?
Launch template allows to specify the instance configuration too, like AMI, instance type, key pair, security groups and other parameters used to launch an EC2 instance. It also supports versioning of templates.
Launch configurations are the older versions and are not suggested to be used anymore by AWS
What does it mean if an instance is in Impaired status?
It means that one or more health checks failed
Amazon EC2 Auto Scaling does not immediately terminate instances with an Impaired status. Instead, Amazon EC2 Auto Scaling waits a few minutes for the instance to recover. Amazon EC2 Auto Scaling might also delay or not terminate instances that fail to report data for status checks. This usually happens when there is insufficient data for the status check metrics in Amazon CloudWatch.
An EC2 instance ELB status is unhealthy, but is not terminated by the ASG. Why?
By default, Amazon EC2 Auto Scaling doesn’t use the results of ELB health checks to determine an instance’s health status when the group’s health check configuration is set to EC2. As a result, Amazon EC2 Auto Scaling doesn’t terminate instances that fail ELB health checks. If an instance’s status is OutofService on the ELB console, but the instance’s status is Healthy on the Amazon EC2 Auto Scaling console, confirm that the health check type is set to ELB.
There are multiple instances. If an ASG needs to scale in, which criteria does it use to decide which instance to terminate?
Per the default termination policy, the first priority is given to any allocation strategy for On-Demand vs Spot instances.
Next, you need to consider any instance which has the oldest launch configuration
The next priority is to consider any instance with the oldest launch template unless there is an instance that uses a launch configuration.
Next is the closest to the next billing hour
Can you assign an Elastic IP to an Application Load Balancer
Only to a Network Load Bolance, you cannot assign it to ALB
What’s the difference between Launch Configuration and Launch Template for ASG?
Launch configuration must be recreated every time
Launch template can be saved and reused by other auto scaling groups, it can have multiple versions and can provision both On-Demand and Sport instances (or a mix)
You want to have two versions of an application deployed at the same time and diverge 50% traffic to each of them, how can you do it?
Two ways:
1. ALB supports Weighted Traffic Groups routing. You can specify a percentage of traffic to direct in each traffic group. This is useful since it saves us from creating a new ALB
2. Route 53 Weighted routing
