Fix possible deadlock

CHANGELOG.md

@@ -1,3 +1,11 @@
+## v0.12.0 [unreleased]
+
+### Features
+
+### Bugfixes
+
+- [#5963](https://github.com/influxdata/influxdb/pull/5963): Fix possible deadlock
+
 ## v0.11.0 [unreleased]
 
 ### Features

tsdb/engine.go

@@ -38,9 +38,6 @@ type Engine interface {
 	DeleteMeasurement(name string, seriesKeys []string) error
 	SeriesCount() (n int, err error)
 
-	// PerformMaintenance will get called periodically by the store
-	PerformMaintenance()
-
 	// Format will return the format for the engine
 	Format() EngineFormat
 

tsdb/engine/tsm1/engine.go

@@ -102,10 +102,6 @@ func NewEngine(path string, walPath string, opt tsdb.EngineOptions) tsdb.Engine
 // Path returns the path the engine was opened with.
 func (e *Engine) Path() string { return e.path }
 
-// PerformMaintenance is for periodic maintenance of the store. A no-op for b1
-func (e *Engine) PerformMaintenance() {
-}
-
 // Index returns the database index.
 func (e *Engine) Index() *tsdb.DatabaseIndex {
 	e.mu.Lock()

tsdb/meta.go

@@ -304,8 +304,11 @@ func (d *DatabaseIndex) measurementsByTagFilters(filters []*TagFilter) Measureme
 	return measurements
 }
 
-// measurementsByRegex returns the measurements that match the regex.
-func (d *DatabaseIndex) measurementsByRegex(re *regexp.Regexp) Measurements {
+// MeasurementsByRegex returns the measurements that match the regex.
+func (d *DatabaseIndex) MeasurementsByRegex(re *regexp.Regexp) Measurements {
+	d.mu.RLock()
+	defer d.mu.RUnlock()
+
 	var matches Measurements
 	for _, m := range d.measurements {
 		if re.MatchString(m.Name) {

tsdb/shard.go

@@ -122,12 +122,6 @@ func NewShard(id uint64, index *DatabaseIndex, path string, walPath string, opti
 // Path returns the path set on the shard when it was created.
 func (s *Shard) Path() string { return s.path }
 
-// PerformMaintenance gets called periodically to have the engine perform
-// any maintenance tasks like WAL flushing and compaction
-func (s *Shard) PerformMaintenance() {
-	s.engine.PerformMaintenance()
-}
-
 // Open initializes and opens the shard's store.
 func (s *Shard) Open() error {
 	if err := func() error {

tsdb/store.go

@@ -90,7 +90,6 @@ func (s *Store) Open() error {
 		return err
 	}
 
-	go s.periodicMaintenance()
 	s.opened = true
 
 	return nil
@@ -567,46 +566,11 @@ func (s *Store) deleteSeries(database string, seriesKeys []string) error {
 	return nil
 }
 
-// periodicMaintenance is the method called in a goroutine on the opening of the store
-// to perform periodic maintenance of the shards.
-func (s *Store) periodicMaintenance() {
-	t := time.NewTicker(maintenanceCheckInterval)
-	for {
-		select {
-		case <-t.C:
-			s.performMaintenance()
-		case <-s.closing:
-			t.Stop()
-			return
-		}
-	}
-}
-
-// performMaintenance loops through shards and executes any maintenance
-// tasks. Those tasks should run in their own goroutines if they will
-// take significant time.
-func (s *Store) performMaintenance() {
-	s.mu.Lock()
-	defer s.mu.Unlock()
-	for _, sh := range s.shards {
-		s.performMaintenanceOnShard(sh)
-	}
-}
-
-func (s *Store) performMaintenanceOnShard(shard *Shard) {
-	defer func() {
-		if r := recover(); r != nil {
-			s.Logger.Printf("recovered error in maintenance on shard %d", shard.id)
-		}
-	}()
-	shard.PerformMaintenance()
-}
-
 // ExpandSources expands regex sources and removes duplicates.
 // NOTE: sources must be normalized (db and rp set) before calling this function.
 func (s *Store) ExpandSources(sources influxql.Sources) (influxql.Sources, error) {
-	s.mu.Lock()
-	defer s.mu.Unlock()
+	s.mu.RLock()
+	defer s.mu.RUnlock()
 	return s.expandSources(sources)
 }
 
@@ -631,7 +595,7 @@ func (s *Store) expandSources(sources influxql.Sources) (influxql.Sources, error
 			}
 
 			// Loop over matching measurements.
-			for _, m := range db.measurementsByRegex(src.Regex.Val) {
+			for _, m := range db.MeasurementsByRegex(src.Regex.Val) {
 				other := &influxql.Measurement{
 					Database:        src.Database,
 					RetentionPolicy: src.RetentionPolicy,