What Is Scalability?
Scalability is the ability of a software solution to respond to increased workloads without impacting performance or availability. It allows businesses to quickly and easily add extra processing resources to their systems in order to handle increased loads.
How Does Amazon EC2 Autoscaling Work?
Amazon EC2 Auto Scaling is a tool that helps businesses scale their Amazon EC2 instances in response to changes in their application demand. It allows organizations to maintain a higher level of application availability by automatically adding or deleting EC2 instances as needed. There are three scaling techniques that can be used with Amazon EC2 Auto Scaling: Dynamic Scaling, Predictive Scaling, and Scheduled Scaling.
Benefits of Auto Scaling EC2:
Better Availability
Amazon EC2 Auto Scaling ensures that your application has enough capacity to handle current traffic demand at all times. This means your application can add or remove new and old instances respectively with respect to the demand of the application, allowing for better availability of the application.
Healthy Instance Replacement
If an instance becomes unhealthy, Auto Scaling EC2 will detect which instance is not performing efficiently and will automatically terminate the instance and replace it with a new one. This ensures that the application is always working at its maximum capacity.
Multiple Availability Zones
Using Amazon EC2 Auto Scaling, you can use multiple availability zones to ensure that your application is always available. If one zone goes down, EC2 Auto Scaling will launch instances in other availability zones to manage the traffic until the crashed zone is healthy again.
Cost-Efficient Auto Scaling is an incredibly cost-efficient way of managing your application’s capacity. Amazon EC2 Auto Scaling can dynamically increase and decrease capacity according to the current demand, meaning you only use and pay for the instances you need. As soon as the traffic to the application decreases, some instances will be terminated, saving you money.
explained in detail below:
Dynamic Scaling
Dynamic Scaling enables you to scale your application as per changing environments and demands. It allows you to track the demand curve for your application and thus helps you to scale your EC2 instances ahead of time. Target tracking scaling policies can be used to choose the desired loaded statistic for the application, such as CPU utilization. Alternatively, you can use the new “Request Count Per Target” measure in Amazon EC2’s Application Load Balancer for Load Balancing. Amazon EC2 Auto Scaling will then adjust the number of EC2 instances as required to keep you on track.
Predictive Scaling
Predictive Scaling assists you in scheduling the right number of EC2 instances based on anticipated demand. You can combine both dynamic and predictive scaling methods for faster scaling of the application. Predictive Scaling forecasts future traffic and allocates the appropriate number of EC2 instances beforehand. Machine learning algorithms in Predictive Scaling detect changes in daily and weekly patterns and automatically update projections. This effectively eliminates the need to manually scale the instances on particular days.
Scheduled Scaling
Scheduled Scaling enables you to scale your application based on the pre-defined schedule. For example, a coffee shop owner may employ more baristas on weekends due to increased demand and let them go on weekdays due to decreased demand. With Amazon EC2 Auto Scaling, you can take a more flexible approach to scale your applications as computing power is a programmable resource in the cloud. When you add Amazon EC2 Auto Scaling to your application, you can create new instances as and when needed, and terminate them when they are no longer in use. This way, you only pay for the instances that you use, when you need them.
Limitations of EC2 Autoscaling:
# Limitations of Amazon EC2 Auto Scaling
Amazon EC2 Auto Scaling has several limitations that should be considered when determining whether it is a good fit for your application.
## Maximum Number of Instances
The maximum number of instances that can be supported by Auto Scaling per Auto Scaling group is 500.
## Instance Health Checks
Auto Scaling uses Amazon EC2 instance health checks to determine the health of an instance. If an instance fails a health check, Auto Scaling will terminate it and launch a new one, but this process can take some time, potentially impacting the availability of your application.
## Scaling Policies
Auto Scaling allows you to set scaling policies based on CloudWatch metrics, but these policies can be complex to configure and may not always scale your application as expected.
## Application Dependencies
If your application has dependencies on other resources or services, such as a database or cache, it may not scale as expected if those resources become overloaded or unavailable.
## Cost Considerations
Using Auto Scaling can increase the cost of running your application, as you may be charged for the additional instances that are launched.
How does EC2 Autoscaling work?
1. Balancing Capacity Across Availability Zones
Amazon EC2 Auto Scaling helps to ensure that each Availability Zone receives the same number of instances, resulting in a balanced distribution of traffic and burden. This helps to maximize the performance of your applications and minimize downtime.
2. Replace and Repair Unhealthy Instances
Amazon EC2 Auto Scaling will automatically identify and replace any unhealthy instances with healthy ones. This helps to reduce the risk of crashing, and eliminates the need for manual health checks or replacements.
3. Monitor Instance Health
Amazon EC2 Auto Scaling regularly monitors the health of all running instances to ensure that they are functioning properly and that traffic is evenly allocated. This helps to ensure optimal performance and minimize downtime.
