Architecting Zero-Downtime Deployments with Node.js Cluster and Signal Handling

Leverage the cluster module to fork multiple processes and use SIGINT/SIGTERM for graceful shutdowns of existing connections before restarting workers.

In a production environment, a simple restart causes dropped connections. To achieve zero-downtime, a Master process manages Workers. When a deploy occurs, the Master sends a signal to workers. Workers stop accepting new connections via server.close(), finish pending requests, and then exit. Simultaneously, the Master forks new workers using the updated code. This 'rolling restart' ensures the application is always available. The Master process should also monitor for unexpected exits and refork workers to maintain high availability.