Create Cron Jobs with PM2: As an Alternative to launchd

I wanted to run scheduled jobs on macOS, but launchd is still hard to read, and I wanted an easier path, so I decided to use PM2 instead.

Configuration for running a Cron job with PM2

cd $PROJECT_ROOT

pm2 ecosystem

Manage the configuration in ecosystem.config.cjs.

module.exports = {
  apps: [
    {
      name: "cronJob",
      script: "main.ts",
      interpreter: "~/.bun/bin/bun",
      // number of instances is 1
      instances: 1,
      // run every 15 minutes
      cron_restart: "*/15 * * * *",
      exec_mode: "fork",
      // restart automatically when target files change: no
      watch: false,
      // restart automatically: no
      autorestart: false,
    },
  ],
};

Points

cron_restart: set the interval in cron format
autorestart: false: since this is a cron-style job, automatic restart is disabled
interpreter: you can specify any runtime, including Bun

Start command:

pm2 start ecosystem.config.cjs

pm2 save

Sample job implementation

This sample periodically fetches the IP address and stores it in a database.

import { Database } from 'bun:sqlite';

const DDL = `CREATE TABLE IF NOT EXISTS ip_history (
  id INTEGER PRIMARY KEY AUTOINCREMENT,
  ip TEXT NOT NULL,
  created_at DATETIME DEFAULT CURRENT_TIMESTAMP
);`

async function fetchIpConfig() {
  const response = await fetch("https://ifconfig.io/ip").catch((err) => new Error(err));
  if (response instanceof Error || !response.ok) {
    return null;
  }

  const ip = await response.text();

  return ip;
}

async function main() {
  const ip = await fetchIpConfig();
  if (ip == null) return;

  using db = new Database('ip-monitor.sqlite', { create: true });
  db.exec(DDL);
  using query = db.query("INSERT INTO ip_history (ip) VALUES ($ip);");
  query.run({ $ip: ip });
}

await main();

References

Summary

With PM2, cron-style jobs can be managed with a simpler setup than launchd.

Define the job in ecosystem.config.cjs, then use PM2’s process management features for logs and restarts when needed.