🍃 Tellia / 🥷🏿 Engineering

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Scheduling Tasks ​

Concept ​

Scheduling task is a simple concept:

Run a job at ${date} with ${payload}`

But since we want to make tellia horitonzally scallable we must ensure two or more instance of a service will run.

That means if you're scheduling any mutating operation, such as:

  • calling a client
  • update in db
  • call to apis
  • api call
  • anything scheduled

We need to make sure the execution happens without concurrency.

Solution ​

This can be solved many ways, and it often includes a queue system (RabbitMQ, Google Pubsub, BullMQ, Redis Streams)

Tellia currently uses the native BullMQ job scheduler to schedule jobs.

typescript
await this.queue.upsertJobScheduler(
  'my-bootstrap-job-v1', // Unique ID prevents duplicates
  {
    pattern: 'some-cron-pattern', // Run as soon as possible
    limit: 1, // Only execute once, then auto-remove
  },
  { data: MyJobSchema.parse({}) },
);

Active jobs ​

Active jobs can be seen on bullboard, see URLS

What you see: alt text

  • The card title is the queue name.
  • Purple jobs are scheduled jobs enqueued

Then, you can click on a queue and click the DELAYED tab.

  • Data tab shows the job's data
  • In Options you can see when the job will be triggered

alt text