I have a job with > 10 tasks in it that interacts with an external system outside of databricks.  At the moment that external system cannot handle more than 3 of the tasks executing concurrently.  How can I limit the number of tasks that concurrently execute in a job?  I'm not particularly worried about the order in which they execute, only that the number at any one time is limited to 3.

The cluster that I execute this on currently has only 1 worker in it and I'm looking to limit what takes place on that single worker.