feat: regularly scheduled jobs (cron)

[benjie]

Description

Adds cron-like functionality to Graphile Worker, enabling you to schedule jobs on a recurring schedule. Read about it in detail in the included README changes.

This is intended to be used via a crontab file, an example of which is in the README, but you can also do it via the crontab: string library option, or if you need more advanced usage you can use the parsedCrontabItems: ParsedCronItem[] library option; to populate that you'd use parseCrontab(crontab: string) or parseCronItems(items: CronItem[]), for example:

run({
  connectionString: "postgres://localhost/graphile_worker",
  parsedCronItems: parseCronItems([
    {
      task: "send_reminder",
      pattern: "10 10 * * *", // send at 10:10am every day
    },
  ]),
});

Performance impact

If unused, should not impact main worker performance measurably. If used, could probably be more optimal, but it's pretty efficient.

Security impact

No known issues.

[benjie]

I don't really know how best to attack the remaining tests for this.

[ben-pr-p]

Thanks for working a parser into this! I'm sure it will save me at least some time if not a real bug 🥇