Access control: Add permissions cache hit/miss metrics (#80883)

* Access control: Add permissions cache hit/miss metrics

* Add metrics to OSS

* Fix imports

pkg/services/accesscontrol/acimpl/service.go

@@ -151,11 +151,13 @@ func (s *Service) getCachedUserPermissions(ctx context.Context, user identity.Re
 	if !options.ReloadCache {
 		permissions, ok := s.cache.Get(key)
 		if ok {
+			metrics.MAccessPermissionsCacheUsage.WithLabelValues(accesscontrol.CacheHit).Inc()
 			s.log.Debug("Using cached permissions", "key", key)
 			return permissions.([]accesscontrol.Permission), nil
 		}
 	}
 
+	metrics.MAccessPermissionsCacheUsage.WithLabelValues(accesscontrol.CacheMiss).Inc()
 	s.log.Debug("Fetch permissions from store", "key", key)
 	permissions, err := s.getUserPermissions(ctx, user, options)
 	if err != nil {

pkg/services/accesscontrol/models.go

@@ -13,7 +13,15 @@ import (
 	"github.com/grafana/grafana/pkg/util/errutil"
 )
 
-var ErrInternal = errutil.Internal("accesscontrol.internal")
+const (
+	CacheHit  = "hit"
+	CacheMiss = "miss"
+)
+
+var (
+	ErrInternal        = errutil.Internal("accesscontrol.internal")
+	CacheUsageStatuses = []string{CacheHit, CacheMiss}
+)
 
 // RoleRegistration stores a role and its assignments to built-in roles
 // (Viewer, Editor, Admin, Grafana Admin)