fix: change default minRunningApps to 1

[Julusian]

About Me

This pull request is posted on behalf of the BBC

Type of Contribution

This is a: Bug fix

Current Behavior

When the system is idle, package-manager is restarting the workers on a 10 minute interval.

This is happening because the workers are idle, so trigger the spinDownTime timer. As minRunningApps is 0, the appContainer would approve the request and spin down the worker.

Shortly after, the workforce would update its status and report itself as BAD due to No workers connected to workforce, causing an error to be reported in Sofie.

Then a little later, requestAppTypeForExpectation is called from checkIfNeedToScaleUp which results in a new worker starting and the error being dismissed.

New Behavior

The minRunningApps now defaults to 1, so that the system doesn't get itself into this restart loop.

Testing Instructions

Other Information

Status

• PR is ready to be reviewed.
• The functionality has been tested by the author.
• Relevant unit tests has been added / updated.
• Relevant documentation (code comments, system documentation) has been added / updated.

[Julusian]

I am not 100% sure on whether this fix is the best solution.
Perhaps it should be enforced that the value should never go below 1?
Or maybe hitting 0 workers should be allowed when autoscaling?

[jstarpl]

Or maybe hitting 0 workers should be allowed when autoscaling?

I would argue that changing the algorithm for the workforce error message/status so that if minRunningApps is 0, this doesn't make it go BAD would be preferable? This would mean that if there are no expectations to be fulfilled, it could just scale down to 0, until such time as when there's work to be done (or checked for it's status).

[nytamin]

I just har a quick talk with Julian, and I think I agree with both Julian and Jan.

1. We should change the behavior so that workerCount === 0 is not a BAD thing.
2. We should modify the defaults of PackageManagerSingleApp to be a "recommended config for a typical use case", so something like
   minRunningApps=1
   maxRunningApps=3
   minCriticalWorkerApps=1