Alerting: Configurable externalLabels for Loki state history (#62404)

* Add config option for external labels

* Remove redundant nilcheck

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

@@ -29,15 +29,17 @@ type remoteLokiClient interface {
 }
 
 type RemoteLokiBackend struct {
-	client remoteLokiClient
-	log    log.Logger
+	client         remoteLokiClient
+	externalLabels map[string]string
+	log            log.Logger
 }
 
 func NewRemoteLokiBackend(cfg LokiConfig) *RemoteLokiBackend {
 	logger := log.New("ngalert.state.historian", "backend", "loki")
 	return &RemoteLokiBackend{
-		client: newLokiClient(cfg, logger),
-		log:    logger,
+		client:         newLokiClient(cfg, logger),
+		externalLabels: cfg.ExternalLabels,
+		log:            logger,
 	}
 }
 
@@ -62,7 +64,7 @@ func (h *RemoteLokiBackend) statesToStreams(rule history_model.RuleMeta, states
 			continue
 		}
 
-		labels := removePrivateLabels(state.State.Labels)
+		labels := h.addExternalLabels(removePrivateLabels(state.State.Labels))
 		labels[OrgIDLabel] = fmt.Sprint(rule.OrgID)
 		labels[RuleUIDLabel] = fmt.Sprint(rule.UID)
 		labels[GroupLabel] = fmt.Sprint(rule.Group)
@@ -124,6 +126,13 @@ func (h *RemoteLokiBackend) recordStreams(ctx context.Context, streams []stream,
 	return nil
 }
 
+func (h *RemoteLokiBackend) addExternalLabels(labels data.Labels) data.Labels {
+	for k, v := range h.externalLabels {
+		labels[k] = v
+	}
+	return labels
+}
+
 type lokiEntry struct {
 	SchemaVersion int              `json:"schemaVersion"`
 	Previous      string           `json:"previous"`

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

@@ -20,6 +20,7 @@ type LokiConfig struct {
 	BasicAuthUser     string
 	BasicAuthPassword string
 	TenantID          string
+	ExternalLabels    map[string]string
 }
 
 type httpLokiClient struct {