Rejects push requests with streams without labels. (#3643)

* Rejects push requests with  streams without labels.

Fixes #3638

Signed-off-by: Cyril Tovena <cyril.tovena@gmail.com>

* Missing commit

Signed-off-by: Cyril Tovena <cyril.tovena@gmail.com>

pkg/distributor/validator.go

@@ -81,6 +81,10 @@ func (v Validator) ValidateEntry(ctx validationContext, labels string, entry log
 
 // Validate labels returns an error if the labels are invalid
 func (v Validator) ValidateLabels(ctx validationContext, ls labels.Labels, stream logproto.Stream) error {
+	if len(ls) == 0 {
+		validation.DiscardedSamples.WithLabelValues(validation.MissingLabels, ctx.userID).Inc()
+		return httpgrpc.Errorf(http.StatusBadRequest, validation.MissingLabelsErrorMsg)
+	}
 	numLabelNames := len(ls)
 	if numLabelNames > ctx.maxLabelNamesPerSeries {
 		validation.DiscardedSamples.WithLabelValues(validation.MaxLabelNamesPerSeries, ctx.userID).Inc()

pkg/distributor/validator_test.go

@@ -16,8 +16,10 @@ import (
 	"github.com/grafana/loki/pkg/validation"
 )
 
-var testStreamLabels = "FIXME"
-var testTime = time.Now()
+var (
+	testStreamLabels = "FIXME"
+	testTime         = time.Now()
+)
 
 func TestValidator_ValidateEntry(t *testing.T) {
 	tests := []struct {
@@ -95,6 +97,13 @@ func TestValidator_ValidateLabels(t *testing.T) {
 			"{foo=\"bar\"}",
 			nil,
 		},
+		{
+			"empty",
+			"test",
+			nil,
+			"{}",
+			httpgrpc.Errorf(http.StatusBadRequest, validation.MissingLabelsErrorMsg),
+		},
 		{
 			"test too many labels",
 			"test",

pkg/validation/validate.go

@@ -7,7 +7,10 @@ import (
 const (
 	discardReasonLabel = "reason"
 	// InvalidLabels is a reason for discarding log lines which have labels that cannot be parsed.
-	InvalidLabels         = "invalid_labels"
+	InvalidLabels = "invalid_labels"
+	MissingLabels = "missing_labels"
+
+	MissingLabelsErrorMsg = "error at least one label pair is required per stream"
 	InvalidLabelsErrorMsg = "Error parsing labels '%s' with error: %s"
 	// RateLimited is one of the values for the reason to discard samples.
 	// Declared here to avoid duplication in ingester and distributor.