[SOLVED] Ensure That Node Cron Job is Only Configured Once

Issue

I'm writing a Discord bot and having it schedule a cron job when it starts up using node-cron. I've defined it as follows (very basic so far):

    cron.schedule('15 1,3,5,7,9,11,13,15,17,19,21,23 * * *', () => {
        GameUpdater.sendGameUpdatesToLeagueChannels(this.guilds);
    });

The problem is, Discord bots will often reconnect which will rerun the portion of the code where this has to be. I'm considering having a check of an external value, perhaps in my database, that manages whether or not it's run recently or is already running or something like that, but I was wondering if there was a proper way to make a cron job unique using node-cron?

Solution

First, you need somewhere to save the name of the scheduled task, which defaults to a UUID V4 but can be provided as an option using the 3rd argument of the schedule method you are calling above.

With a reference to this name, either from a database or a constant that is hard-coded in the script you have wrote, you can use cron.getTasks to list all of the scheduled tasks to ensure that the current task doesn't already exist before scheduling it.

If you are referencing a hard-coded name, then calling the schedule method will replace the existing scheduled task, rather than creating a new task.

UPDATE

To set the name of the scheduled task, simply pass in an options object as a third argument to the schedule method you are calling, with a name for your task.

Example:

cron.schedule('15 1,3,5,7,9,11,13,15,17,19,21,23 * * *', () => {
    GameUpdater.sendGameUpdatesToLeagueChannels(this.guilds);
}, { name: "example-task-1234" });

Answered By - Alex Ander

Answer Checked By - Clifford M. (WPSolving Volunteer)