Alerting: Add max limit for Loki query size in state history API (#89646)

* add setting for query limit

* update BuildLogQuery to return error if limit is exceeded

* move tests for BuildLogQuery to separate suite

pkg/services/annotations/annotationsimpl/loki/historian_store.go

@@ -45,6 +45,7 @@ var (
 
 type lokiQueryClient interface {
 	RangeQuery(ctx context.Context, query string, start, end, limit int64) (historian.QueryRes, error)
+	MaxQuerySize() int
 }
 
 // LokiHistorianStore is a read store that queries Loki for alert state history.
@@ -98,8 +99,12 @@ func (r *LokiHistorianStore) Get(ctx context.Context, query *annotations.ItemQue
 		}
 	}
 
-	logQL, err := historian.BuildLogQuery(buildHistoryQuery(query, accessResources.Dashboards, rule.UID))
+	logQL, err := historian.BuildLogQuery(buildHistoryQuery(query, accessResources.Dashboards, rule.UID), r.client.MaxQuerySize())
 	if err != nil {
+		grafanaErr := errutil.Error{}
+		if errors.As(err, &grafanaErr) {
+			return make([]*annotations.ItemDTO, 0), err
+		}
 		return make([]*annotations.ItemDTO, 0), ErrLokiStoreInternal.Errorf("failed to build loki query: %w", err)
 	}
 

pkg/services/annotations/annotationsimpl/loki/historian_store_test.go

@@ -778,6 +778,7 @@ func NewFakeLokiClient() *FakeLokiClient {
 			ReadPathURL:    url,
 			Encoder:        historian.JsonEncoder{},
 			MaxQueryLength: 721 * time.Hour,
+			MaxQuerySize:   65536,
 		},
 		metrics: metrics,
 		log:     log.New("ngalert.state.historian", "backend", "loki"),
@@ -812,6 +813,10 @@ func (c *FakeLokiClient) RangeQuery(ctx context.Context, query string, from, to,
 	return res, nil
 }
 
+func (c *FakeLokiClient) MaxQuerySize() int {
+	return c.cfg.MaxQuerySize
+}
+
 func TestUseStore(t *testing.T) {
 	t.Run("false if state history disabled", func(t *testing.T) {
 		cfg := setting.UnifiedAlertingStateHistorySettings{