Include metric name, label name, number of entries and limit in cardinality errors.

pkg/chunk/chunk_store_test.go

@@ -47,35 +47,27 @@ var stores = []struct {
 	{
 		name: "store",
 		configFn: func() StoreConfig {
-			var (
-				storeCfg StoreConfig
-			)
+			var storeCfg StoreConfig
 			flagext.DefaultValues(&storeCfg)
 			return storeCfg
 		},
 	},
 	{
 		name: "cached_store",
 		configFn: func() StoreConfig {
-			var (
-				storeCfg StoreConfig
-			)
+			var storeCfg StoreConfig
 			flagext.DefaultValues(&storeCfg)
-
 			storeCfg.WriteDedupeCacheConfig.Cache = cache.NewFifoCache("test", cache.FifoCacheConfig{
 				Size: 500,
 			})
-
 			return storeCfg
 		},
 	},
 }
 
 // newTestStore creates a new Store for testing.
 func newTestChunkStore(t *testing.T, schemaName string) Store {
-	var (
-		storeCfg StoreConfig
-	)
+	var storeCfg StoreConfig
 	flagext.DefaultValues(&storeCfg)
 	return newTestChunkStoreConfig(t, schemaName, storeCfg)
 }

pkg/chunk/series_store.go

@@ -7,7 +7,6 @@ import (
 	"net/http"
 
 	"github.com/go-kit/kit/log/level"
-	"github.com/pkg/errors"
 	"github.com/prometheus/client_golang/prometheus"
 	"github.com/prometheus/client_golang/prometheus/promauto"
 	"github.com/prometheus/common/model"
@@ -22,11 +21,19 @@ import (
 	"github.com/cortexproject/cortex/pkg/util/validation"
 )
 
-var (
-	// ErrCardinalityExceeded is returned when the user reads a row that
-	// is too large.
-	ErrCardinalityExceeded = errors.New("cardinality limit exceeded")
+// CardinalityExceededError is returned when the user reads a row that
+// is too large.
+type CardinalityExceededError struct {
+	MetricName, LabelName string
+	Size, Limit           int32
+}
+
+func (e CardinalityExceededError) Error() string {
+	return fmt.Sprintf("cardinality limit exceeded for %s{%s}; %d entries, more than limit of %d",
+		e.MetricName, e.LabelName, e.Size, e.Limit)
+}
 
+var (
 	indexLookupsPerQuery = promauto.NewHistogram(prometheus.HistogramOpts{
 		Namespace: "cortex",
 		Name:      "chunk_store_index_lookups_per_query",
@@ -196,6 +203,7 @@ func (c *seriesStore) lookupSeriesByMetricNameMatchers(ctx context.Context, from
 	var preIntersectionCount int
 	var lastErr error
 	var cardinalityExceededErrors int
+	var cardinalityExceededError CardinalityExceededError
 	for i := 0; i < len(matchers); i++ {
 		select {
 		case incoming := <-incomingIDs:
@@ -210,8 +218,9 @@ func (c *seriesStore) lookupSeriesByMetricNameMatchers(ctx context.Context, from
 			// series and the other returns only 10 (a few), we don't lookup the first one at all.
 			// We just manually filter through the 10 series again using "filterChunksByMatchers",
 			// saving us from looking up and intersecting a lot of series.
-			if err == ErrCardinalityExceeded {
+			if e, ok := err.(CardinalityExceededError); ok {
 				cardinalityExceededErrors++
+				cardinalityExceededError = e
 			} else {
 				lastErr = err
 			}
@@ -220,7 +229,7 @@ func (c *seriesStore) lookupSeriesByMetricNameMatchers(ctx context.Context, from
 
 	// But if every single matcher returns a lot of series, then it makes sense to abort the query.
 	if cardinalityExceededErrors == len(matchers) {
-		return nil, ErrCardinalityExceeded
+		return nil, cardinalityExceededError
 	} else if lastErr != nil {
 		return nil, lastErr
 	}
@@ -241,11 +250,14 @@ func (c *seriesStore) lookupSeriesByMetricNameMatcher(ctx context.Context, from,
 	}
 
 	var queries []IndexQuery
+	var labelName string
 	if matcher == nil {
 		queries, err = c.schema.GetReadQueriesForMetric(from, through, userID, model.LabelValue(metricName))
 	} else if matcher.Type != labels.MatchEqual {
+		labelName = matcher.Name
 		queries, err = c.schema.GetReadQueriesForMetricLabel(from, through, userID, model.LabelValue(metricName), model.LabelName(matcher.Name))
 	} else {
+		labelName = matcher.Name
 		queries, err = c.schema.GetReadQueriesForMetricLabelValue(from, through, userID, model.LabelValue(metricName), model.LabelName(matcher.Name), model.LabelValue(matcher.Value))
 	}
 	if err != nil {
@@ -254,7 +266,11 @@ func (c *seriesStore) lookupSeriesByMetricNameMatcher(ctx context.Context, from,
 	level.Debug(log).Log("queries", len(queries))
 
 	entries, err := c.lookupEntriesByQueries(ctx, queries)
-	if err != nil {
+	if e, ok := err.(CardinalityExceededError); ok {
+		e.MetricName = metricName
+		e.LabelName = labelName
+		return nil, e
+	} else if err != nil {
 		return nil, err
 	}
 	level.Debug(log).Log("entries", len(entries))

pkg/chunk/storage/caching_fixtures.go

@@ -40,5 +40,6 @@ var Fixtures = []testutils.Fixture{
 func defaultLimits() (*validation.Overrides, error) {
 	var defaults validation.Limits
 	flagext.DefaultValues(&defaults)
+	defaults.CardinalityLimit = 5
 	return validation.NewOverrides(defaults)
 }

pkg/chunk/storage/caching_index_client.go

@@ -88,7 +88,10 @@ func (s *cachingIndexClient) QueryPages(ctx context.Context, queries []chunk.Ind
 	batches, misses := s.cacheFetch(ctx, keys)
 	for _, batch := range batches {
 		if cardinalityLimit > 0 && batch.Cardinality > cardinalityLimit {
-			return chunk.ErrCardinalityExceeded
+			return chunk.CardinalityExceededError{
+				Size:  batch.Cardinality,
+				Limit: cardinalityLimit,
+			}
 		}
 
 		queries := queriesByKey[batch.Key]
@@ -156,7 +159,10 @@ func (s *cachingIndexClient) QueryPages(ctx context.Context, queries []chunk.Ind
 			if cardinalityLimit > 0 && cardinality > cardinalityLimit {
 				batch.Cardinality = cardinality
 				batch.Entries = nil
-				cardinalityErr = chunk.ErrCardinalityExceeded
+				cardinalityErr = chunk.CardinalityExceededError{
+					Size:  cardinality,
+					Limit: cardinalityLimit,
+				}
 			}
 
 			keys = append(keys, key)

pkg/chunk/storage/index_client_test.go

@@ -2,10 +2,14 @@ package storage
 
 import (
 	"fmt"
+	"strconv"
 	"testing"
+	"time"
 
-	"github.com/cortexproject/cortex/pkg/chunk"
 	"github.com/stretchr/testify/require"
+
+	"github.com/cortexproject/cortex/pkg/chunk"
+	"github.com/cortexproject/cortex/pkg/chunk/cache"
 )
 
 func TestIndexBasic(t *testing.T) {
@@ -194,3 +198,32 @@ func TestQueryPages(t *testing.T) {
 		}
 	})
 }
+
+func TestCardinalityLimit(t *testing.T) {
+	forAllFixtures(t, func(t *testing.T, client chunk.IndexClient, _ chunk.ObjectClient) {
+		limits, err := defaultLimits()
+		require.NoError(t, err)
+
+		client = newCachingIndexClient(client, cache.NewMockCache(), time.Minute, limits)
+		batch := client.NewWriteBatch()
+		for i := 0; i < 10; i++ {
+			batch.Add(tableName, "bar", []byte(strconv.Itoa(i)), []byte(strconv.Itoa(i)))
+		}
+		err = client.BatchWrite(ctx, batch)
+		require.NoError(t, err)
+
+		var have int
+		err = client.QueryPages(ctx, []chunk.IndexQuery{{
+			TableName: tableName,
+			HashValue: "bar",
+		}}, func(_ chunk.IndexQuery, read chunk.ReadBatch) bool {
+			iter := read.Iterator()
+			for iter.Next() {
+				have++
+			}
+			return true
+		})
+		require.Error(t, err, "cardinality limit exceeded for {}; 10 entries, more than limit of 5")
+		require.Equal(t, 0, have)
+	})
+}