Pulumi: Updating a dependency stack does not force updates of dependents

[lukehoban]

We added StackReference recently, which is nice for creating a dependency between two stacks. However, this does not enforce that when a dependency stack updates, that all the stacks that have outstanding StackReferences on it also update.

Ideally, we would automate this to the greatest degree possible, ultimately down to the level of cascading resources updates across stacks. There are some challenges with this in the near term, but we should look at some/all of the below as part of this.

1. Warnings/errors if you update a stack output that is being depended on, letting you know which other stacks you will need to update.
2. Webhooks to notify when a stack is updated so you can build your own notification and/or automation solutions on top of this.
3. Feedback about stale references in app.pulumi.com
4. Support for "umbrella" projects that describe how a constellation of Pulumi stacks are deployed and inter-related which can allow a single update of the umbrella stack to drive cascading updates across child stacks.
5. If/when we support a hosted deployment option (where the deployment runs remotely via pulumi.com or a customer-controlled agent), allow updates of dependencies to automatically trigger and/or coordinate across multiple stack updates.

[pbzdyl]

I think automated updated on all dependent stacks would be too much as it often needs to be scheduled later. Info output with all dependent stacks would be very helpful.

[nguyenxndaidev]

I think automated updated on all dependent stacks would be too much as it often needs to be scheduled later. Info output with all dependent stacks would be very helpful.

It would be nice if Pulumi could provide all options in the order below:

• First, show information about the problems of dependencies.
• Second, suggest solution, that user can do it manually if he want.
• Third, ask user if he want Pulumi runs the automated update.

[radarcg]

How does Pulumi recommend detecting and handling cascading dependencies?