consul/.changelog/14956.txt

```release-note:bug
cache: refactor agent cache fetching to prevent unnecessary fetches on error
```
cache: refactor agent cache fetching to prevent unnecessary fetches on error (#14956) This continues the work done in #14908 where a crude solution to prevent a goroutine leak was implemented. The former code would launch a perpetual goroutine family every iteration (+1 +1) and the fixed code simply caused a new goroutine family to first cancel the prior one to prevent the leak (-1 +1 == 0). This PR refactors this code completely to: - make it more understandable - remove the recursion-via-goroutine strangeness - prevent unnecessary RPC fetches when the prior one has errored. The core issue arose from a conflation of the entry.Fetching field to mean: - there is an RPC (blocking query) in flight right now - there is a goroutine running to manage the RPC fetch retry loop The problem is that the goroutine-leak-avoidance check would treat Fetching like (2), but within the body of a goroutine it would flip that boolean back to false before the retry sleep. This would cause a new chain of goroutines to launch which #14908 would correct crudely. The refactored code uses a plain for-loop and changes the semantics to track state for "is there a goroutine associated with this cache entry" instead of the former. We use a uint64 unique identity per goroutine instead of a boolean so that any orphaned goroutines can tell when they've been replaced when the expiry loop deletes a cache entry while the goroutine is still running and is later replaced. 2022-10-25 10:27:26 -05:00			```release-note:bug
			`cache: refactor agent cache fetching to prevent unnecessary fetches on error`
			```