Cron para Serverless: GitHub Actions, Vercel Cron y Cloudflare Workers

Las expresiones cron son el lenguaje universal para programar tareas recurrentes. Cada plataforma serverless tiene sus propias peculiaridades.

Conceptos básicos de cron

Una expresión cron estándar tiene 5 campos:

┌───────────── minute (0-59)
│ ┌───────────── hour (0-23)
│ │ ┌───────────── day of month (1-31)
│ │ │ ┌───────────── month (1-12)
│ │ │ │ ┌───────────── day of week (0-6, Sun=0)
│ │ │ │ │
* * * * *

Caracteres especiales comunes:

• * — cualquier valor
• */5 — cada 5 unidades
• 1,3,5 — valores específicos
• 1-5 — rango de valores

Prueba tus expresiones cron con nuestro Cron Parser →

Plataforma 1: GitHub Actions

GitHub Actions usa el evento schedule.

Configuración

# .github/workflows/scheduled.yml
name: Scheduled Job
on:
  schedule:
    - cron: '30 5 * * 1-5'  # Weekdays at 5:30 AM UTC
    - cron: '0 12 1 * *'    # 1st of every month at noon UTC
jobs:
  run:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - run: echo "Running scheduled task"

Limitaciones

Horarios comunes

# Every 5 minutes
- cron: '*/5 * * * *'

# Every hour at minute 0
- cron: '0 * * * *'

# Daily at midnight UTC
- cron: '0 0 * * *'

# Daily at 9 AM Eastern (UTC-5, no DST)
- cron: '0 14 * * *'

# Weekdays at 8 AM UTC
- cron: '0 8 * * 1-5'

# Every Monday and Thursday at 6 PM UTC
- cron: '0 18 * * 1,4'

# First day of every month at midnight
- cron: '0 0 1 * *'

Tip: GitHub Actions puede retrasarse.

Plataforma 2: Vercel Cron Jobs

Configuración en vercel.json.

Configuración

// vercel.json
{
  "crons": [
    {
      "path": "/api/daily-report",
      "schedule": "0 8 * * *"
    },
    {
      "path": "/api/cleanup",
      "schedule": "0 0 * * 0"
    }
  ]
}

Ruta API

// app/api/daily-report/route.ts
import { NextResponse } from 'next/server';

export async function GET() {
  // Your scheduled logic here
  await sendDailyReport();
  return NextResponse.json({ ok: true });
}

// Vercel recommends setting maxDuration for long tasks
export const maxDuration = 60; // seconds

Limitaciones

Important: Vercel usa UTC. Hobby: 1/día.

Plataforma 3: Cloudflare Workers

Configuración en wrangler.toml.

Configuración

# wrangler.toml
name = "my-worker"
main = "src/index.ts"

[triggers]
crons = [
  "*/5 * * * *",    # Every 5 minutes
  "0 12 * * 1-5",   # Weekdays at noon UTC
  "0 0 1 * *"       # First of every month
]

Código Worker

// src/index.ts
export default {
  async scheduled(
    controller: ScheduledController,
    env: Env,
    ctx: ExecutionContext
  ) {
    // controller.cron contains the cron pattern that triggered
    switch (controller.cron) {
      case '*/5 * * * *':
        await doHealthCheck(env);
        break;
      case '0 12 * * 1-5':
        await sendReport(env);
        break;
    }
  },
};

Limitaciones

Comparación plataformas

Trampa de zonas horarias

Las tres usan exclusivamente UTC.

El horario de verano cambia los offsets UTC.

10 expresiones cron listas

Horarios más comunes:

# Every 5 minutes
*/5 * * * *

# Every hour at :00
0 * * * *

# Every day at midnight UTC
0 0 * * *

# Every day at noon UTC
0 12 * * *

# Weekdays (Mon-Fri) at 9 AM UTC
0 9 * * 1-5

# Every Monday at 8 AM UTC
0 8 * * 1

# Every 6 hours
0 */6 * * *

# First day of every month at midnight
0 0 1 * *

# Every 15 minutes during business hours (8-17 UTC)
*/15 8-17 * * 1-5

# Last day of month at 11 PM UTC (approximate)
0 23 28-31 * *

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