PM2

PM2 is a production process manager for Node.js with over 120 million npm downloads, created in 2014 by Alexandre Strzelewicz at Unitech and commercialized through Keymetrics. The tool manages application lifecycles across multiple CPU cores using the built-in Node.js cluster module, achieving zero-downtime reloads in under 200 milliseconds by gracefully draining existing TCP connections before recycling worker processes. In cluster mode, it spawns one worker per logical CPU core with configurable instance counts up to 255 per machine, routing connections through the round-robin scheduler from Node.js 0.12. The max memory restart threshold monitors RSS memory per process and automatically recycles workers exceeding configurable limits, preventing leaks from crashing production servers. The startup hook generator creates systemd unit files, upstart scripts, and launchd plists for process resurrection after reboots, supporting Ubuntu 16.04 through 24.04, CentOS 7 and 8, Debian 10 through 12, Amazon Linux 2, and macOS. The deployment command executes multi-stage SSH deployments with pre-deploy, post-deploy, and pre-setup hooks for database migrations and cache warming. The ecosystem configuration uses JavaScript syntax with environment variable expansion and per-environment overrides. Log management streams stdout and stderr to time-rotated files with JSON output for aggregation pipelines and flush intervals as low as 50 milliseconds. PayPal manages over 8,000 Node.js processes across 400 production servers with 99.99 percent uptime since migrating from Forever in 2015. The module ecosystem includes over 500 community packages for log rotation, Datadog APM, New Relic, health checks, and auto-scaling. Version 5.4.3 in 2024 added native ESM support. MIT licensed. Copyright 2014-2026 Keymetrics.