Auto Scaling helps to automatically scale your Amazon EC2 capacity by scaling out or scaling in according to condition defined. When traffic volume is high the Auto scaling features increases the EC2 instance for that period to maintain application performance and decreases the EC2 instance when demands null.
Auto Scaling plans:
There are several plan which defines how auto scaling is done, some of them are described below.
Maintain Current Instance Levels
Auto Scaling group is configured in such a way that it can maintain a minimum or specified number of running instances at all times. To achieve this Auto Scaling performs a periodic health check on running instances within an Auto Scaling group. When Auto Scaling finds an unhealthy instance, it terminates that instance and launches a new one.
In this we specify the change in the maximum, minimum, or desired capacity of your Auto Scaling group. Auto Scaling manages the process of creating or terminating instances to maintain the updated capacity.
When it is desired to Scale out the EC2 instance or Scale in Amazon EC2 instance on some specific period of time, we can do that. Examples include periodic events such as end-of-month, end-of-quarter, or end-of-year processing, and also other predictable, recurring events.
Dynamic scaling lets you define parameters that control the Auto Scaling process in a scaling policy. For example, you might create a policy that adds more Amazon EC2 instances to the web tier when the network bandwidth, measured by Amazon Cloud Watch, reaches a certain threshold.