Defining a Cron Job

To run recurring tasks in your app, cron jobs can be defined as part of the joystick.app() startup process. Cron jobs should live in the /cron_jobs folder (alias: cronJobs) at the root of your app.

If your app requires a significant number of cron jobs, it's recommended to split them into individual files and then import them into a /cron_jobs/index.js file and combine them together using a JavaScript spread ....

import fetch from 'node-fetch';
import fs from 'fs';

const EVERY_TWELVE_HOURS = '0 */12 * * *';
const { writeFile } = fs.promises;

const cron_jobs = {
  update_usd_to_eur_exchange_rate: {
    log_at_run_time: 'Updating USD -> EUR exchange rate...',
    schedule: EVERY_TWELVE_HOURS,
    run: async () => {
      const usd_to_eur_rate = await fetch('https://exchange-rates.imaginary-api.com?from=usd&to=eur).then((response) => {
        return response.json();
      });
      
      await writeFile('lib/exchange_rates/usd_to_eur.json', JSON.stringify(usd_to_eur_rate));
    },
  },
};

export default cron_jobs;

A cron job is defined as a key/value pair on an object where the key name is the name of the cron job and the value is an object defining the cron job.

Above, we've defined a cron job update_usd_to_eur_exchange_rate with three options:

1. log_at_run_time a string we want to log to our server logs every time the cron job runs.
2. schedule a crontab string defining the schedule for the cron job.
3. run a function that's called for each "tick" or run of the cron job.

In order for a cron job to run, it must be registered via the options you pass to joystick.app().