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/setting/setting_unified_alerting.go

@@ -60,6 +60,7 @@ const (
 	SchedulerBaseInterval = 10 * time.Second
 	// DefaultRuleEvaluationInterval indicates a default interval of for how long a rule should be evaluated to change state from Pending to Alerting
 	DefaultRuleEvaluationInterval = SchedulerBaseInterval * 6 // == 60 seconds
+	stateHistoryDefaultEnabled    = true
 )
 
 type UnifiedAlertingSettings struct {
@@ -85,6 +86,7 @@ type UnifiedAlertingSettings struct {
 	DefaultRuleEvaluationInterval time.Duration
 	Screenshots                   UnifiedAlertingScreenshotSettings
 	ReservedLabels                UnifiedAlertingReservedLabelSettings
+	StateHistory                  UnifiedAlertingStateHistorySettings
 }
 
 type UnifiedAlertingScreenshotSettings struct {
@@ -98,6 +100,10 @@ type UnifiedAlertingReservedLabelSettings struct {
 	DisabledLabels map[string]struct{}
 }
 
+type UnifiedAlertingStateHistorySettings struct {
+	Enabled bool
+}
+
 // IsEnabled returns true if UnifiedAlertingSettings.Enabled is either nil or true.
 // It hides the implementation details of the Enabled and simplifies its usage.
 func (u *UnifiedAlertingSettings) IsEnabled() bool {
@@ -304,6 +310,12 @@ func (cfg *Cfg) ReadUnifiedAlertingSettings(iniFile *ini.File) error {
 	}
 	uaCfg.ReservedLabels = uaCfgReservedLabels
 
+	stateHistory := iniFile.Section("unified_alerting.state_history")
+	uaCfgStateHistory := UnifiedAlertingStateHistorySettings{
+		Enabled: stateHistory.Key("enabled").MustBool(stateHistoryDefaultEnabled),
+	}
+	uaCfg.StateHistory = uaCfgStateHistory
+
 	cfg.UnifiedAlerting = uaCfg
 	return nil
 }