A Highly Available Web Application Using Auto Scaling and Elastic Load Balancing
The first scenario we’ll consider is a highly available web application that you’ll implement using the topology shown in Figure 12.1.
Don’t worry if this looks intimidating. We’ll start by taking a high-level look at how these components fit together, and then we’ll dig into the configuration specifics. EC2 Auto Scaling will initially provision two EC2 instances running in different Availability Zones inside the default VPC. Every default VPC has a default subnet in each Availability Zone, so there’s no need to create subnets explicitly. An application load balancer will proxy the connections from clients on the internet and distribute those connections to the instances that are running the popular open-source Apache web server.
We’ll implement this scenario...