lib/storage: remove metricID with missing metricID->metricName entry

The metricID->metricName entry can be missing in the indexdb after unclean shutdown
when only a part of entries for new time series is written into indexdb.

Recover from such a situation by removing the broken metricID. New metricID
will be automatically created for time series with the given metricName
when new data point will arive to it.

app/vmselect/netstorage/netstorage.go

@@ -462,16 +462,12 @@ func getStorageSearch() *storage.Search {
 }
 
 func putStorageSearch(sr *storage.Search) {
-	n := atomic.LoadUint64(&sr.MissingMetricNamesForMetricID)
-	missingMetricNamesForMetricID.Add(int(n))
 	sr.MustClose()
 	ssPool.Put(sr)
 }
 
 var ssPool sync.Pool
 
-var missingMetricNamesForMetricID = metrics.NewCounter(`vm_missing_metric_names_for_metric_id_total`)
-
 // ProcessSearchQuery performs sq on storage nodes until the given deadline.
 func ProcessSearchQuery(sq *storage.SearchQuery, fetchData bool, deadline Deadline) (*Results, error) {
 	// Setup search.

app/vmstorage/main.go

@@ -414,6 +414,10 @@ func registerStorageMetrics() {
 		return float64(idbm().DateRangeSearchHits)
 	})
 
+	metrics.NewGauge(`vm_missing_metric_names_for_metric_id_total`, func() float64 {
+		return float64(idbm().MissingMetricNamesForMetricID)
+	})
+
 	metrics.NewGauge(`vm_date_metric_id_cache_syncs_total`, func() float64 {
 		return float64(m().DateMetricIDCacheSyncsCount)
 	})

lib/storage/index_db.go

@@ -101,6 +101,11 @@ type indexDB struct {
 	// The number of hits for date range searches.
 	dateRangeSearchHits uint64
 
+	// missingMetricNamesForMetricID is a counter of missing MetricID -> MetricName entries.
+	// High rate may mean corrupted indexDB due to unclean shutdown.
+	// The db must be automatically recovered after that.
+	missingMetricNamesForMetricID uint64
+
 	mustDrop uint64
 
 	// Start date fully covered by per-day inverted index.
@@ -228,6 +233,8 @@ type IndexDBMetrics struct {
 	DateRangeSearchCalls uint64
 	DateRangeSearchHits  uint64
 
+	MissingMetricNamesForMetricID uint64
+
 	IndexBlocksWithMetricIDsProcessed      uint64
 	IndexBlocksWithMetricIDsIncorrectOrder uint64
 
@@ -269,6 +276,8 @@ func (db *indexDB) UpdateMetrics(m *IndexDBMetrics) {
 	m.DateRangeSearchCalls += atomic.LoadUint64(&db.dateRangeSearchCalls)
 	m.DateRangeSearchHits += atomic.LoadUint64(&db.dateRangeSearchHits)
 
+	m.MissingMetricNamesForMetricID += atomic.LoadUint64(&db.missingMetricNamesForMetricID)
+
 	m.IndexBlocksWithMetricIDsProcessed = atomic.LoadUint64(&indexBlocksWithMetricIDsProcessed)
 	m.IndexBlocksWithMetricIDsIncorrectOrder = atomic.LoadUint64(&indexBlocksWithMetricIDsIncorrectOrder)
 
@@ -888,6 +897,13 @@ func (db *indexDB) searchMetricName(dst []byte, metricID uint64) ([]byte, error)
 	// Cannot find MetricName for the given metricID. This may be the case
 	// when indexDB contains incomplete set of metricID -> metricName entries
 	// after a snapshot or due to unflushed entries.
+	atomic.AddUint64(&db.missingMetricNamesForMetricID, 1)
+
+	// Mark the metricID as deleted, so it will be created again when new data point
+	// for the given time series will arrive.
+	if err := db.deleteMetricIDs([]uint64{metricID}); err != nil {
+		return dst, fmt.Errorf("cannot delete metricID for missing metricID->metricName entry; metricID=%d; error: %s", metricID, err)
+	}
 	return dst, io.EOF
 }
 
@@ -912,9 +928,28 @@ func (db *indexDB) DeleteTSIDs(tfss []*TagFilters) (int, error) {
 	if err != nil {
 		return 0, err
 	}
+	if err := db.deleteMetricIDs(metricIDs); err != nil {
+		return 0, err
+	}
+
+	// Delete TSIDs in the extDB.
+	deletedCount := len(metricIDs)
+	if db.doExtDB(func(extDB *indexDB) {
+		var n int
+		n, err = extDB.DeleteTSIDs(tfss)
+		deletedCount += n
+	}) {
+		if err != nil {
+			return deletedCount, fmt.Errorf("cannot delete tsids in extDB: %s", err)
+		}
+	}
+	return deletedCount, nil
+}
+
+func (db *indexDB) deleteMetricIDs(metricIDs []uint64) error {
 	if len(metricIDs) == 0 {
 		// Nothing to delete
-		return 0, nil
+		return nil
 	}
 
 	// Mark the found metricIDs as deleted.
@@ -924,12 +959,11 @@ func (db *indexDB) DeleteTSIDs(tfss []*TagFilters) (int, error) {
 		items.B = encoding.MarshalUint64(items.B, metricID)
 		items.Next()
 	}
-	err = db.tb.AddItems(items.Items)
+	err := db.tb.AddItems(items.Items)
 	putIndexItems(items)
 	if err != nil {
-		return 0, err
+		return err
 	}
-	deletedCount := len(metricIDs)
 
 	// atomically add deleted metricIDs to an inmemory map.
 	dmis := &uint64set.Set{}
@@ -943,18 +977,7 @@ func (db *indexDB) DeleteTSIDs(tfss []*TagFilters) (int, error) {
 
 	// Do not reset uselessTagFiltersCache, since the found metricIDs
 	// on cache miss are filtered out later with deletedMetricIDs.
-
+	return nil
-	// Delete TSIDs in the extDB.
-	if db.doExtDB(func(extDB *indexDB) {
-		var n int
-		n, err = extDB.DeleteTSIDs(tfss)
-		deletedCount += n
-	}) {
-		if err != nil {
-			return deletedCount, fmt.Errorf("cannot delete tsids in extDB: %s", err)
-		}
-	}
-	return deletedCount, nil
 }
 
 func (db *indexDB) getDeletedMetricIDs() *uint64set.Set {

lib/storage/search.go

@@ -3,7 +3,6 @@ package storage
 import (
 	"fmt"
 	"io"
-	"sync/atomic"
 
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/bytesutil"
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/encoding"
@@ -89,11 +88,6 @@ type Search struct {
 	err error
 
 	needClosing bool
-
-	// MissingMetricNamesForMetricID is a counter of missing MetricID -> MetricName
-	// entries during the search.
-	// High rate may mean corrupted indexDB.
-	MissingMetricNamesForMetricID uint64
 }
 
 func (s *Search) reset() {
@@ -104,7 +98,6 @@ func (s *Search) reset() {
 	s.ts.reset()
 	s.err = nil
 	s.needClosing = false
-	s.MissingMetricNamesForMetricID = 0
 }
 
 // Init initializes s from the given storage, tfss and tr.
@@ -161,8 +154,8 @@ func (s *Search) NextMetricBlock() bool {
 		s.MetricBlock.MetricName, err = s.storage.searchMetricName(s.MetricBlock.MetricName[:0], tsid.MetricID)
 		if err != nil {
 			if err == io.EOF {
-				// Missing metricName for tsid.MetricID. Increment error counter and skip it.
+				// Skip missing metricName for tsid.MetricID.
-				atomic.AddUint64(&s.MissingMetricNamesForMetricID, 1)
+				// It should be automatically fixed. See indexDB.searchMetricName for details.
 				continue
 			}
 			s.err = err