PMM-14431 Fix and related test.

Author: JiriCtvrtka

exporter/collstats_collector_test.go

@@ -25,7 +25,10 @@ import (
 	"github.com/prometheus/client_golang/prometheus/testutil"
 	"github.com/prometheus/common/promslog"
 	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
 	"go.mongodb.org/mongo-driver/bson"
+	"go.mongodb.org/mongo-driver/mongo"
+	"go.mongodb.org/mongo-driver/mongo/options"
 
 	"github.com/percona/mongodb_exporter/internal/tu"
 )
@@ -93,3 +96,61 @@ mongodb_collstats_storageStats_capped{collection="testcol_02",database="testdb"}
 	err := testutil.CollectAndCompare(c, expected, filter...)
 	assert.NoError(t, err)
 }
+
+func TestCollStatsForFakeCountType(t *testing.T) {
+	t.Parallel()
+	ctx, cancel := context.WithTimeout(t.Context(), 3*time.Second)
+	defer cancel()
+
+	client := tu.DefaultTestClient(ctx, t)
+
+	database := client.Database("testdb")
+	database.Drop(ctx) //nolint
+
+	defer func() {
+		err := database.Drop(ctx)
+		require.NoError(t, err)
+	}()
+
+	collName := "test_collection_account"
+	coll := database.Collection(collName)
+
+	_, err := coll.InsertOne(ctx, bson.M{"account_id": 1, "count": 10})
+	require.NoError(t, err)
+	_, err = coll.InsertOne(ctx, bson.M{"account_id": 2, "count": 20})
+	require.NoError(t, err)
+
+	indexModel := mongo.IndexModel{
+		Keys:    bson.D{{Key: "account_id", Value: 1}},
+		Options: options.Index().SetName("test_index_account"),
+	}
+	_, err = coll.Indexes().CreateOne(ctx, indexModel)
+	require.NoError(t, err)
+
+	indexModel = mongo.IndexModel{
+		Keys:    bson.D{{Key: "count", Value: 1}},
+		Options: options.Index().SetName("test_index_count"),
+	}
+	_, err = coll.Indexes().CreateOne(ctx, indexModel)
+	require.NoError(t, err)
+
+	ti := labelsGetterMock{}
+
+	collection := []string{"testdb.test_collection_account"}
+	logger := promslog.New(&promslog.Config{})
+	c := newCollectionStatsCollector(ctx, client, logger, false, ti, collection, false)
+
+	expected := strings.NewReader(`
+       # HELP mongodb_collstats_storageStats_indexSizes collstats.storageStats.indexSizes
+       # TYPE mongodb_collstats_storageStats_indexSizes untyped
+       mongodb_collstats_storageStats_indexSizes{collection="test_collection_account",database="testdb",index_name="_id_"} 4096
+       mongodb_collstats_storageStats_indexSizes{collection="test_collection_account",database="testdb",index_name="test_index_account"} 20480
+       mongodb_collstats_storageStats_indexSizes{collection="test_collection_account",database="testdb",index_name="test_index_count"} 20480
+       `)
+
+	filter := []string{
+		"mongodb_collstats_storageStats_indexSizes",
+	}
+	err = testutil.CollectAndCompare(c, expected, filter...)
+	require.NoError(t, err)
+}

exporter/metrics.go

@@ -17,6 +17,7 @@ package exporter
 
 import (
 	"regexp"
+	"slices"
 	"strings"
 	"sync"
 	"time"
@@ -220,7 +221,10 @@ func makeRawMetric(prefix, name string, value interface{}, labels map[string]str
 	fqName, label := nameAndLabel(prefix, name)
 
 	metricType := prometheus.UntypedValue
-	if strings.HasSuffix(strings.ToLower(name), "count") {
+
+	// reservedPrefixes are used for metrics that might include the word ‘count’ in their name but are not actual counters.
+	reservedPrefixes := []string{"collstats.storageStats.indexSizes."}
+	if !slices.Contains(reservedPrefixes, prefix) && strings.HasSuffix(strings.ToLower(name), "count") {
 		metricType = prometheus.CounterValue
 	}