Publish an application availability metric to Amazon CloudWatch in the DR Region from the application environment in the primary Region. Create a CloudWatch alarm in the DR Region that is invoked when the application availability metric stops being delivered. Configure the CloudWatch alarm to send a notification to an Amazon Simple Notification Service (Amazon SNS) topic in the DR Region. Add an email subscription to the SNS topic that sends messages to the application owner. Upon notification instruct a systems operator to sign in to the AWS Management Console and initiate failover operations for the application.

Create a cron task that runs every 5 minutes by using one of the applications EC2 instances in the primary Region. Configure the corn task to check whether the application is available. Upon failure, the cron task notifies a systems operator and attempts to restart the application services.

Create a cron task that runs every 5 minutes by using one of the application's EC2 instances in the primary Region. Configure the cron task to check whether the application is available. Upon failure, the cron task modifies the DR environment by promoting the read replica and by adding EC2 instances to the Auto Scaling group.

publish an application available metric to Amazon CloudWatch in the DR Region from the application environment in the primary Region. Create a CloudWatch alarm in the DR Region that in invoked when the application availability metric steps being delivered. Configure the CloudWatch alarm to send a notification to an Amazon Simple and to add EC2 instances to the Auto Scaling group.