HotswapRefConstructor

Access the current input value I on its own

Access the current resource value R on its own

Swap R using I using some function of I to cats.effect.kernel.Resource of R, provided at construction time

Access R safely

Note that access to R is protected by a shared-mode lock via a cats.effect.kernel.Resource scope. A resource R with unreleased locks cannot be finalized and therefore cannot be fully swapped.

Swap the current resource with a new version

This makes use of evalTap on the provided cats.effect.kernel.Resource to ensure the cats.effect.kernel.Ref with R is updated immediately on allocation and may be used by access calls while swap blocks, waiting for the previous cats.effect.kernel.Resource to finalize.

This means that while there is no previous finalization process in progress when this is called, R may be swapped in the holder ref, but will block until all references to R are removed and R is torn down.

A semaphore guarantees that concurrent access to swap will wait while previous resources are finalized.