ELB and ASG - Elastic Load Balancing and auto scaling groups Flashcards
What is vertical scaling
Increase instance size
What is horizontal scaling
Increase number of instances
High availability
Run instances for the same application across multi AZ
Describe agility
new IT resources are only a click away, which means that you reduce the time to male those resources available to your developers from weeks to just minutes
What is a load balancing
Load balancers are servers that forward internet traffic to multiple servers (EC2 instances) downstream
Why would you use a load abalancer
Spread load across multiple downstream instances
Expose a single point of access (DNS) to your app
Seamlessly handle failures of downstream instances
Do regular health checks to your instances
Provide SSL termination ( HTTPS) for your websites
High availability across zones
What is and Why use an Elastic Load Balancer
An ELB ( ELastic Load balancer is managed load balancer
AWS guarantees that it will be working
AWS takes care of upgrades, maintenance, high availability
AWS provide only a few config knobs
It costs less to setup your own load balancer but it will be alot more effort on your end
What are the three kinds of load balancers offered by AWS
App load balancer (HTTP/HTTPS only) - Layer 7
Network Load balancer ( ultra-high performance, allows for TCP) - layer 4
Classic Load balancer (slowly retiring) - Layer 4 and 7
What is an autoscaling group
contains a collection of Amazon EC2 instances that are treated as a logical grouping for the purposes of automatic scaling
What are the goals of an AutoScaling Group (ASG)
Scale out (add EC2 instances) to match an increase load
Scale in (remove EC2 instances) to match a decreased load
Ensure we have a minimum and maximum number of machines running
Automatically register new instances to a load balancer
Replace unhealthy instances
Cost savings- only run at an optimal capacity (principle of the cloud)
