fix: guard against failed ingester requests for detected fields

pkg/querier/querier.go

@@ -14,6 +14,7 @@ import (
 	"github.com/go-kit/log/level"
 	"github.com/google/uuid"
 	"github.com/grafana/dskit/httpgrpc"
+	"github.com/grafana/dskit/multierror"
 	"github.com/grafana/dskit/tenant"
 	"github.com/opentracing/opentracing-go"
 	"github.com/pkg/errors"
@@ -1076,7 +1077,7 @@ func (q *SingleTenantQuerier) DetectedFields(ctx context.Context, req *logproto.
 	if err != nil {
 		return nil, err
 	}
-	// just incject the header to categorize labels
+	// just inject the header to categorize labels
 	ctx = httpreq.InjectHeader(ctx, httpreq.LokiEncodingFlagsHeader, (string)(httpreq.FlagCategorizeLabels))
 	params := logql.SelectLogParams{
 		QueryRequest: &logproto.QueryRequest{
@@ -1091,14 +1092,59 @@ func (q *SingleTenantQuerier) DetectedFields(ctx context.Context, req *logproto.
 		},
 	}
 
-	iters, err := q.SelectLogs(ctx, params)
-	if err != nil {
-		return nil, err
+	ingesterQueryInterval, storeQueryInterval := q.buildQueryIntervals(params.Start, params.End)
+	sp := opentracing.SpanFromContext(ctx)
+	iters := []iter.EntryIterator{}
+	errs := multierror.New()
+	if !q.cfg.QueryStoreOnly && ingesterQueryInterval != nil {
+		// Make a copy of the request before modifying
+		// because the initial request is used below to query stores
+		queryRequestCopy := *params.QueryRequest
+		newParams := logql.SelectLogParams{
+			QueryRequest: &queryRequestCopy,
+		}
+		newParams.Start = ingesterQueryInterval.start
+		newParams.End = ingesterQueryInterval.end
+		if sp != nil {
+			sp.LogKV(
+				"msg", "querying ingester for detected fields",
+				"params", newParams)
+		}
+		ingesterIters, err := q.ingesterQuerier.SelectLogs(ctx, newParams)
+		if err != nil {
+			errs.Add(err)
+		} else {
+			iters = append(iters, ingesterIters...)
+		}
+	}
+
+	if !q.cfg.QueryIngesterOnly && storeQueryInterval != nil {
+		params.Start = storeQueryInterval.start
+		params.End = storeQueryInterval.end
+		if sp != nil {
+			sp.LogKV(
+				"msg", "querying store for detected fields",
+				"params", params)
+		}
+		storeIter, err := q.store.SelectLogs(ctx, params)
+		if err != nil {
+			errs.Add(err)
+		} else {
+			iters = append(iters, storeIter)
+		}
+	}
+
+  //return an empty response instead of an error, so if there are results in other splits, they can be returned
+	if len(iters) == 0 {
+		level.Warn(q.logger).Log("msg", "no detected field results from store or ingester", "error", errs.Err())
+		return &logproto.DetectedFieldsResponse{
+			Fields:     []*logproto.DetectedField{},
+			FieldLimit: req.GetFieldLimit(),
+		}, nil
 	}
 
-	// TODO(twhitney): converting from a step to a duration should be abstracted and reused,
-	// doing this in a few places now.
-	streams, err := streamsForFieldDetection(iters, req.LineLimit)
+	mergedIter := iter.NewMergeEntryIterator(ctx, iters, logproto.BACKWARD)
+	streams, err := streamsForFieldDetection(mergedIter, req.LineLimit)
 	if err != nil {
 		return nil, err
 	}