Merge pull request #9465 from influxdata/js-write-to-shard-during-delete

Mark a shard as in process of being deleted

tsdb/store.go

@@ -54,6 +54,10 @@ type Store struct {
 	// shared per-database indexes, only if using "inmem".
 	indexes map[string]interface{}
 
+	// Maintains a set of shards that are in the process of deletion.
+	// This prevents new shards from being created while old ones are being deleted.
+	pendingShardDeletes map[uint64]struct{}
+
 	EngineOptions EngineOptions
 
 	baseLogger *zap.Logger
@@ -69,13 +73,14 @@ type Store struct {
 func NewStore(path string) *Store {
 	logger := zap.NewNop()
 	return &Store{
-		databases:     make(map[string]struct{}),
-		path:          path,
-		sfiles:        make(map[string]*SeriesFile),
-		indexes:       make(map[string]interface{}),
-		EngineOptions: NewEngineOptions(),
-		Logger:        logger,
-		baseLogger:    logger,
+		databases:           make(map[string]struct{}),
+		path:                path,
+		sfiles:              make(map[string]*SeriesFile),
+		indexes:             make(map[string]interface{}),
+		pendingShardDeletes: make(map[uint64]struct{}),
+		EngineOptions:       NewEngineOptions(),
+		Logger:              logger,
+		baseLogger:          logger,
 	}
 }
 
@@ -465,6 +470,12 @@ func (s *Store) CreateShard(database, retentionPolicy string, shardID uint64, en
 		return nil
 	}
 
+	// Shard may be undergoing a pending deletion. While the shard can be
+	// recreated, it must wait for the pending delete to finish.
+	if _, ok := s.pendingShardDeletes[shardID]; ok {
+		return fmt.Errorf("shard %d is pending deletion and cannot be created again until finished", shardID)
+	}
+
 	// Create the db and retention policy directories if they don't exist.
 	if err := os.MkdirAll(filepath.Join(s.path, database, retentionPolicy), 0700); err != nil {
 		return err
@@ -537,11 +548,29 @@ func (s *Store) DeleteShard(shardID uint64) error {
 	}
 
 	// Remove the shard from Store so it's not returned to callers requesting
-	// shards.
+	// shards. Also mark that this shard is currently being deleted in a separate
+	// map so that we do not have to retain the global store lock while deleting
+	// files.
 	s.mu.Lock()
+	if _, ok := s.pendingShardDeletes[shardID]; ok {
+		// We are already being deleted? This is possible if delete shard
+		// was called twice in sequence before the shard could be removed from
+		// the mapping.
+		// This is not an error because deleting a shard twice is not an error.
+		s.mu.Unlock()
+		return nil
+	}
 	delete(s.shards, shardID)
+	s.pendingShardDeletes[shardID] = struct{}{}
 	s.mu.Unlock()
 
+	// Ensure the pending deletion flag is cleared on exit.
+	defer func() {
+		s.mu.Lock()
+		defer s.mu.Unlock()
+		delete(s.pendingShardDeletes, shardID)
+	}()
+
 	// Get the shard's local bitset of series IDs.
 	index, err := sh.Index()
 	if err != nil {