Create a view in Tableau that pulls in data from Tableau's database.

Here are instructions on how to setup a connection to the database:

https://onlinehelp.tableau.com/current/server/en-us/adminview_postgres_connect.htm

Once your connection is established, query the _background_tasks table. The column "finish_code" will have 0 or 1. 1 means "fail."

Here is a sample query to use in a view:

SELECT title, subtitle, notes FROM _background_tasks WHERE finish_code = 1 AND job_name = 'Refresh Extracts'

This will provide you with all failed extract refreshes and why they failed. Take a look at the _background_tasks table to see what other information you can pull from it, including site, when it was created, when it finished, etc.

Now that you have the information available to alert on, create an alert in Metric Insights. If your view doesn't have a time-series, you will need to have Metric Insights 'snapshot' the data--add a date column when it is collected.

The alert rule would be against a 'fixed value' where the value is more than 0.