follow-up: cancel health checks when a resource is not running

[adamint]

Description

Currently, we only cancel health checks when the ResourceHealthCheckService is stopped. We should instead start to run health checks on a resource whenever it gets into the Running state and stop running them when they are no longer Running.

I created a linked cancellation token to represent the lifecycle of an individual resource's periodical health check runs. It is added when the resource is determined to be Running, and it is cancelled (and health reports' statuses are set to null) when the resource is not.

Additionally, adds several more health check tests for different scenarios, including that reports are updated where the health status did not change but a report status did, and re-enables ResourcesWithHealthCheck_NotHealthyUntilCheckSucceeds and so fixes #6385

Fixes #6450

Checklist

• Is this feature complete?
  • Yes. Ready to ship.
  • No. Follow-up changes expected.
• Are you including unit tests for the changes and scenario tests if relevant?
  • Yes
  • No
• Did you add public API?
  • Yes
    • If yes, did you have an API Review for it?
      • Yes
      • No
    • Did you add <remarks /> and <code /> elements on your triple slash comments?
      • Yes
      • No
  • No
• Does the change make any security assumptions or guarantees?
  • Yes
    • If yes, have you done a threat model and had a security review?
      • Yes
      • No
  • No
• Does the change require an update in our Aspire docs?
  • Yes
    • Link to aspire-docs issue:
  • No

Microsoft Reviewers: Open in CodeFlow

[mitchdenny]

I'm not sure we want to do this. Health checks to resources is possibly a many to many relationship.

It's possibly also worth checking out whether the health check invocation is coming from the DefaultHealthCheckService or the ResourceHealthCheckService.

[adamint]

I'm not sure we want to do this. Health checks to resources is possibly a many to many relationship.

Yes that's true, but resource monitoring happens per-resource. We can cancel/restart monitoring per-resource at will without cancelling health checks on other resources. It is potentially expensive to keep running these checks in perpetuity; definitionally, health status is null for non-Running resources, so it would be nice if we could avoid making these calls when possible.

It's possibly also worth checking out whether the health check invocation is coming from the DefaultHealthCheckService or the ResourceHealthCheckService.

They are coming from ResourceHealthCheckService.

[JamesNK]

I can't comment on app hosting changes. I'm not fimilar with the health checks logic.