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Auto-Scaling and Load Balancing Your Instances
If your expect your application to have significant variability in usage, you might want to use Auto Scaling and Elastic Load Balancing, two features of Amazon EC2 that help manage the variability.
Auto Scaling
Auto Scaling enables you to scale up or down the number of instances you are using based on parameters that you specify, such as traffic or CPU load.
Auto Scaling also monitors the health of each Amazon EC2 instance that it launches. If any instance terminates unexpectedly, Auto Scaling detects the termination and launches a replacement instance.
For a high degree of flexibility, you can organize Amazon EC2 instances into AutoScalingGroups, which enable you to scale different server classes (e.g., web servers, back end servers) at different rates. For each group, you specify the minimum number of instances, the maximum number of instances, and the parameters to increase and decrease the number of running instances.
For information on setting up Auto Scaling, go to the Amazon Auto Scaling Developer Guide.
Load Balancing
Elastic Load Balancing lets you automatically distribute the incoming traffic (or load) among all the instances you are running. The service also makes it easy to add new instances when you need to increase the capacity of your web site application.
Customers reach your web site via your web URL, such as www.mywebsite.com. This single address might actually represent several instances of your running web application. To always have an available web site, you need to run multiple instances. Otherwise, your customers might see delays when accessing your site, or worse, might not be able to access your site at all.
Elastic Load Balancing manages the incoming requests by optimally routing traffic so that no one instance is overwhelmed. You can quickly add more instances to applications that are experiencing an upsurge in traffic or remove capacity when traffic is slow.
For information on setting up Elastic Load Balancing, go to the Elastic Load Balancing Developer Guide.
