How can this be accomplished in an automated fashion?
Create a health check endpoint in the web application that tests connectivity to the data and middleware tiers. Use this endpoint as the health check URL for the load balancer.
Create an approval step for the quality assurance team to validate connectivity. Reject changes in the pipeline if there is an issue with connecting to the dependent tiers.
Use an Amazon RDS active connection count and an Amazon CloudWatch ELB metric to alarm on a significant change to the number of open connections.
Use Amazon Route 53 health checks to detect issues with the web service and roll back the Cl/CD pipeline if there is an error.
Explanations:
Creating a health check endpoint in the web application that tests connectivity to the database and middleware tiers allows for automated verification. This health check endpoint can be used by the load balancer to ensure that the web tier is functioning correctly before it is considered healthy and traffic is routed to it.
An approval step by the quality assurance team introduces manual intervention, which is not fully automated and goes against the goal of automating the CI/CD pipeline. Additionally, this method doesn’t directly verify connectivity between the web tier and other tiers.
While monitoring the active connection count in Amazon RDS and CloudWatch ELB metrics can provide valuable insight, it does not specifically verify the communication between the web tier and other application tiers during deployment. It is more focused on performance and not connectivity.
Amazon Route 53 health checks are designed for DNS routing, not for verifying application-level connectivity between the tiers. Route 53 health checks would not provide a reliable way to verify that the web tier can communicate with the database and middleware tiers, and rolling back based on this would not be effective.