It would be nice to have to ability to send a slack message or an email on an ad hoc basis when a job finishes running. It would be useful when there was an incident, to let a business partner know when the issue was fixed and the data has been updated.

Does this help? https://docs.dagster.io/_apidocs/libraries/dagster-slack

This is great but I’m thinking about a really specific case where you want to subscribe to notifications about one specific job. You would open that job in dagit and subscribe to that specific one without changing any code. Kind of like when you subscribe to active incident on the status page of a company.

Do job alerts work? Or are you looking for finer grained than job failure? https://docs.dagster.io/dagster-cloud/account/setting-up-alerts

It looks like exactly what I want. Is this only for Dagster cloud?

Ah, maybe so. (We're using Dagster Cloud.)

In open source, you can set up a run status sensor: https://docs.dagster.io/concepts/partitions-schedules-sensors/sensors#run-status-sensors