Make the cache eviction logic for stale entities more robust

Fixes #12458

3 files changed, 30 insertions, 16 deletions

diff --git a/resources/resource.go b/resources/resource.go
index 867b262fb..0fee69cdd 100644
--- a/resources/resource.go
+++ b/resources/resource.go
@@ -296,16 +296,19 @@ type hashProvider interface {
 	hash() string
 }
 
+var _ resource.StaleInfo = (*StaleValue[any])(nil)
+
 type StaleValue[V any] struct {
 	// The value.
 	Value V
 
-	// IsStaleFunc reports whether the value is stale.
-	IsStaleFunc func() bool
+	// StaleVersionFunc reports the current version of the value.
+	// This always starts out at 0 and get incremented on staleness.
+	StaleVersionFunc func() uint32
 }
 
-func (s *StaleValue[V]) IsStale() bool {
-	return s.IsStaleFunc()
+func (s *StaleValue[V]) StaleVersion() uint32 {
+	return s.StaleVersionFunc()
 }
 
 type AtomicStaler struct {
@@ -313,11 +316,11 @@ type AtomicStaler struct {
 }
 
 func (s *AtomicStaler) MarkStale() {
-	atomic.StoreUint32(&s.stale, 1)
+	atomic.AddUint32(&s.stale, 1)
 }
 
-func (s *AtomicStaler) IsStale() bool {
-	return atomic.LoadUint32(&(s.stale)) > 0
+func (s *AtomicStaler) StaleVersion() uint32 {
+	return atomic.LoadUint32(&(s.stale))
 }
 
 // For internal use.
diff --git a/resources/resource/resourcetypes.go b/resources/resource/resourcetypes.go
index 0766fe232..5d9533223 100644
--- a/resources/resource/resourcetypes.go
+++ b/resources/resource/resourcetypes.go
@@ -233,17 +233,27 @@ type StaleMarker interface {
 
 // StaleInfo tells if a resource is marked as stale.
 type StaleInfo interface {
-	IsStale() bool
+	StaleVersion() uint32
 }
 
-// IsStaleAny reports whether any of the os is marked as stale.
-func IsStaleAny(os ...any) bool {
-	for _, o := range os {
-		if s, ok := o.(StaleInfo); ok && s.IsStale() {
-			return true
+// StaleVersion returns the StaleVersion for the given os,
+// or 0 if not set.
+func StaleVersion(os any) uint32 {
+	if s, ok := os.(StaleInfo); ok {
+		return s.StaleVersion()
+	}
+	return 0
+}
+
+// StaleVersionSum calculates the sum of the StaleVersionSum for the given oss.
+func StaleVersionSum(oss ...any) uint32 {
+	var version uint32
+	for _, o := range oss {
+		if s, ok := o.(StaleInfo); ok && s.StaleVersion() > 0 {
+			version += s.StaleVersion()
 		}
 	}
-	return false
+	return version
 }
 
 // MarkStale will mark any of the oses as stale, if possible.
diff --git a/resources/transform.go b/resources/transform.go
index d9084b178..b498924f5 100644
--- a/resources/transform.go
+++ b/resources/transform.go
@@ -657,8 +657,9 @@ type resourceAdapterInner struct {
 	*publishOnce
 }
 
-func (r *resourceAdapterInner) IsStale() bool {
-	return r.Staler.IsStale() || r.target.IsStale()
+func (r *resourceAdapterInner) StaleVersion() uint32 {
+	// Both of these are incremented on change.
+	return r.Staler.StaleVersion() + r.target.StaleVersion()
 }
 
 type resourceTransformations struct {