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What does PM2's cluster mode (`pm2 start server.js -i max`) do for a Node.js application, without requiring any manual code changes?
š» Code Challenge | +75 XP
Write an ecosystem.config.js file configuring an application to run in cluster mode using all available CPU cores, with production environment variables, and demonstrate a zero-downtime reload command.
A team running a Node.js application with plain "node server.js" experienced extended downtime whenever an unhandled exception crashed the process, since nobody noticed until a user reported the outage. Reorder the steps to fix this using PM2.
Task: Reorder the blocks in logical sequence to solve the problem.
A.D.A. Interface
Adaptive Didactic Assistant
Pascual Vila
Frontend Instructor // Code Syllabus
The Error //
Running a production Node.js application directly with plain `node server.js`, with no process manager
// Risky: a crash means downtime until someone manually notices and restarts
$ node server.js
// Correct: automatic restart on crash
$ pm2 start server.jsThe Solution //
Without a process manager, an unhandled exception or other crash leaves the application completely down until a human notices and manually restarts it ā potentially a long, unnecessary outage for something a process manager like PM2 would have handled automatically within seconds.
The Error //
Repeating CLI flags manually for every PM2 deploy instead of using an ecosystem config file
// Error-prone: must be remembered and typed correctly every time
$ pm2 start server.js -i max --env production
// Correct: declared once, reproducible, version-controlled
$ pm2 start ecosystem.config.jsThe Solution //
Manually remembering and typing the correct combination of flags (instance count, environment variables, exec mode) for every deploy is error-prone and not reproducible across team members or environments ā an ecosystem.config.js file declares this configuration explicitly, checked into version control.