Add metric name to metadata error (cortexproject#4363)

Signed-off-by: Goutham Veeramachaneni <[email protected]>
Signed-off-by: Alvin Lin <[email protected]>

pkg/ingester/user_metrics_metadata.go

@@ -4,6 +4,8 @@ import (
 	"sync"
 	"time"
 
+	"github.com/prometheus/prometheus/pkg/labels"
+
 	"github.com/cortexproject/cortex/pkg/cortexpb"
 	"github.com/cortexproject/cortex/pkg/util/validation"
 )
@@ -49,7 +51,7 @@ func (mm *userMetricsMetadata) add(metric string, metadata *cortexpb.MetricMetad
 
 	if err := mm.limiter.AssertMaxMetadataPerMetric(mm.userID, len(set)); err != nil {
 		validation.DiscardedMetadata.WithLabelValues(mm.userID, perMetricMetadataLimit).Inc()
-		return makeLimitError(perMetricMetadataLimit, mm.limiter.FormatError(mm.userID, err))
+		return makeMetricLimitError(perMetricMetadataLimit, labels.FromStrings(labels.MetricName, metric), mm.limiter.FormatError(mm.userID, err))
 	}
 
 	// if we have seen this metadata before, it is a no-op and we don't need to change our metrics.