fix(alerting): only expose metrics if executing alerts (#85512)

pkg/services/ngalert/ngalert.go

@@ -279,6 +279,7 @@ func (ng *AlertNG) init() error {
 	cfg := state.ManagerCfg{
 		Metrics:                        ng.Metrics.GetStateMetrics(),
 		ExternalURL:                    appUrl,
+		DisableExecution:               !ng.Cfg.UnifiedAlerting.ExecuteAlerts,
 		InstanceStore:                  ng.store,
 		Images:                         ng.ImageService,
 		Clock:                          clk,

pkg/services/ngalert/state/manager.go

@@ -71,6 +71,8 @@ type ManagerCfg struct {
 	ApplyNoDataAndErrorToAllStates bool
 	RulesPerRuleGroupLimit         int64
 
+	DisableExecution bool
+
 	Tracer tracing.Tracer
 	Log    log.Logger
 }
@@ -78,7 +80,8 @@ type ManagerCfg struct {
 func NewManager(cfg ManagerCfg, statePersister StatePersister) *Manager {
 	// Metrics for the cache use a collector, so they need access to the register directly.
 	c := newCache()
-	if cfg.Metrics != nil {
+	// Only expose the metrics if this grafana server does execute alerts.
+	if cfg.Metrics != nil && !cfg.DisableExecution {
 		c.RegisterMetrics(cfg.Metrics.Registerer())
 	}