Question

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When you run Express apps for production, it is helpful to use a process manager to:

• Restart the app automatically if it crashes.
• Gain insights into runtime performance and resource consumption.
• Modify settings dynamically to improve performance.
• Control clustering.

A process manager is somewhat like an application server: it’s a “container” for applications that facilitates deployment, provides high availability, and enables you to manage the application at runtime.

The most popular process managers for Express and other Node.js applications are:

• Forever: A simple command-line interface tool to ensure that a script runs continuously (forever). Forever’s simple interface makes it ideal for running smaller deployments of Node.js apps and scripts.
• PM2: A production process manager for Node.js applications that has a built-in load balancer. PM2 enables you to keep applications alive forever, reloads them without downtime, helps you to manage application logging, monitoring, and clustering.
• StrongLoop Process Manager (Strong-PM): A production process manager for Node.js applications with built-in load balancing, monitoring, and multi-host deployment. Includes a CLI to build, package, and deploy Node.js applications to a local or remote system.
• SystemD: The default process manager on modern Linux distributions, that makes it simple to run a Node application as a service. For more information, see “Run node.js service with systemd” by Ralph Slooten (@axllent).