Alerting: Allow state history to be disabled through configuration (#61006)

* Add configuration option for if state history should be enabled

* Inject no-op when history is disabled

pkg/services/ngalert/ngalert.go

@@ -200,8 +200,13 @@ func (ng *AlertNG) init() error {
 		AlertSender:          alertsRouter,
 	}
 
-	historian := historian.NewAnnotationHistorian(ng.annotationsRepo, ng.dashboardService)
-	stateManager := state.NewManager(ng.Metrics.GetStateMetrics(), appUrl, store, ng.imageService, clk, historian)
+	var history state.Historian
+	if ng.Cfg.UnifiedAlerting.StateHistory.Enabled {
+		history = historian.NewAnnotationHistorian(ng.annotationsRepo, ng.dashboardService)
+	} else {
+		history = historian.NewNopHistorian()
+	}
+	stateManager := state.NewManager(ng.Metrics.GetStateMetrics(), appUrl, store, ng.imageService, clk, history)
 	scheduler := schedule.NewScheduler(schedCfg, stateManager)
 
 	// if it is required to include folder title to the alerts, we need to subscribe to changes of alert title

pkg/services/ngalert/state/historian/noop.go

@@ -0,0 +1,18 @@
+package historian
+
+import (
+	"context"
+
+	"github.com/grafana/grafana/pkg/services/ngalert/models"
+	"github.com/grafana/grafana/pkg/services/ngalert/state"
+)
+
+// NoOpHistorian is a state.Historian that does nothing with the resulting data, to be used in contexts where history is not needed.
+type NoOpHistorian struct{}
+
+func NewNopHistorian() *NoOpHistorian {
+	return &NoOpHistorian{}
+}
+
+func (f *NoOpHistorian) RecordStatesAsync(ctx context.Context, _ *models.AlertRule, _ []state.StateTransition) {
+}