🔗 Blue-green deployment switcher script

In zero-downtime deployment architectures, switching traffic between two identical environments—Blue (current live) and Green (new release)—is a critical operation. Performing this traffic switch manually via web server configurations or load balancer updates is prone to human error, slow to execute, and lacks immediate automated validation. If a newly deployed environment passes preliminary build steps but fails under actual runtime conditions, manual rollbacks can introduce significant downtime and service disruption.

This script solves the problem by automating the blue-green traffic cutover process. It verifies the health of the target environment before switching traffic, atomically updates the local web server reverse proxy (such as NGINX), validates the live router state after the switch, and automatically triggers an immediate rollback if the new live endpoint exhibits post-switch degradation.