HA And Scaling Flashcards
What is an Elastic Load Balancer (ELB)?
It is a DNS record that points at 1+ nodes per A Z
What is the difference between an internet facing node and an internal node?
internet facing has public IP, internal only has private
Can a private EC2 instance be used with a load balancer?
Yes, because the EC2 instance doesn’t have to accept a public connection, just one coming from load balancer.
What types of protocols is ALB used for?
HTTP/HTTPS.
What can you use to forward traffic to different target groups depending on IP address, or redirect requests?
ALB rules.
What protocols should you use NLB for?
TCP, TLS, UDP…more or less just “non-http/s”.
What has faster latency: ALB or NLB?
NLB.
What are Launch Configurations and Launch Templates used for?
Define config of an EC2 instance in advance
Which can be edited after creation: Launch Templates or Launch Configuration?
Neither, but launch templates support versioning
What is the main use of an auto scaling group (ASG)?
Automatic scaling and self-healing for EC2.
Where is an ASG configured?
Within a VPC.
What is configured within the ASG, so ASG knows where to launch instances?
Subnets from the VPC that the ASG is attached to.
What are the 3 parameters that determine how many instances will be running at once within a subnet attached to an ASG?
Min, max, and desired size
What are the three types of scaling policies?
Manual, Scheduled, and Dynamic
In dynamic scaling, what is the difference between simple and stepped scaling?
Simple is more “binary” e.g. CPU > 50% or <50%. Stepped defines what happens at certain thresholds. E.g. >50% launch 1, >70% launch 2, etc.
YOU WILL
EAT THE BUGS
What is the cooldown period?
How long to wait after performing a scaling action before performing another.
Launch Template will define ____ is launched, while ASG defines ____ and ____
what, when, where
True or False: ASGs NEED scaling policies
False
In ASG, what can you use to backup data when an instance is terminated, or load data on an instance before it is launched?
Lifecycle Hooks
In ASG, what occurs when an instance fails health checks?
It is replaced.
What is a grace period, and why might you use it?
Defines a set of time after instance is launched before starting to perform a health check. You might use it if you want to do additional configuration on an instance before checking.
In load balancing, what is Bridging?
When the load balancer listener is configured for HTTPS, and SSL is passed through to backend instances. Instances need certificates!
In load balancing, what is Pass-through?
Only occurs with NLB. No SSL cert needed on load balancer, but needed on backend instances.
