Auto scaling makes our environment has desired capacity of EC2 isntances when it is needed.
Autoscale supports only horizontal scaling
If auto scaling finds unhealthy instances it is replaced with new instances by terminating the old instance.
Auto scaling service is free. How ever instances launched by auto scaling is chargeable.
Auto Scaling Group:
1. It is a group of EC2 instances which participates in the auto scaling. This group contains Minimum: Minimum number of isntances this group must contain always. Maximum: Maximum number of isntances that can participate in auto scaling. Desired: Is decided at runtime, based on the scaling policies
Note: We can use auto scaling with fixed group size
Launch Configuration: It is a template used by auto scaling for launching new isntances
Launch configuration contains:
1. AMI
2. Instance Type
3. EBS volume
4. Security Group
5. IAM role
6. SSH key pair.
Note: We cannot update launch configuration, we only can configure new one and attach to Auto scaling group
