ASG

Auto Scaling Groups

What’s an Auto Scaling Group?

• In real-life, the load on your websites and applications can change

• In the cloud, you can create and get rid of servers very quickly

• The goal of an Auto Scaling Group (ASG) is to:

• Scale-out (add EC2 instances) to match an increased load

• Scale in (remove EC2 instances) to match a decreased load

• Ensure we have a minimum and a 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)

Auto Scaling Group in AWS

Without Load Balancer

With Load Balancer

Scaling Strategies

• Manual Scaling: Update the size of an ASG manually

• Dynamic Scaling: Respond to changing demand

• Simple / Step Scaling

  • When a CloudWatch alarm is triggered (example CPU > 70%), then add 2 units

  • When a CloudWatch alarm is triggered (example CPU < 30%), then remove 1

• Target Tracking Scaling

  • Example: I want the average ASG CPU to stay at around 40%

• Scheduled Scaling

  • Anticipate a scaling based on known usage patterns

  • Example: increase the min. capacity to 10 at 5 pm on Fridays

• Predictive Scaling

• Uses Machine Learning to predict future traffic ahead of time

• Automatically provisions the right number of EC2 instances in advance

• Useful when your load has predictable time-based patterns