fix: improved shard deletion (#24602)

Avoid unnecessarily deleting series from the series file
Try harder to delete series from InMem indices
Log all errors on shard deletion

Closes #24834

tsdb/store.go

@@ -811,7 +811,7 @@ func (s *Store) DeleteShard(shardID uint64) error {
 		return ErrShardNotFound
 	}
 
-	// Remove the shard from Store so it's not returned to callers requesting
+	// Remove the shard from Store, so it's not returned to callers requesting
 	// 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.
@@ -840,7 +840,6 @@ func (s *Store) DeleteShard(shardID uint64) error {
 		defer s.mu.Unlock()
 		delete(s.epochs, shardID)
 		delete(s.pendingShardDeletes, shardID)
-		s.databases[db].removeIndexType(sh.IndexType())
 	}()
 
 	// Get the shard's local bitset of series IDs.
@@ -851,16 +850,23 @@ func (s *Store) DeleteShard(shardID uint64) error {
 
 	ss := index.SeriesIDSet()
 
-	s.walkShards(shards, func(sh *Shard) error {
+	err = s.walkShards(shards, func(sh *Shard) error {
 		index, err := sh.Index()
 		if err != nil {
+			s.Logger.Error("cannot find shard index", zap.Uint64("shard_id", sh.ID()), zap.Error(err))
 			return err
 		}
 
 		ss.Diff(index.SeriesIDSet())
 		return nil
 	})
 
+	if err != nil {
+		// We couldn't get the index for a shard. Rather than deleting series which may
+		// exist in that shard as well as in the current shard, we stop the current deletion
+		return err
+	}
+
 	// Remove any remaining series in the set from the series file, as they don't
 	// exist in any of the database's remaining shards.
 	if ss.Cardinality() > 0 {
@@ -872,7 +878,7 @@ func (s *Store) DeleteShard(shardID uint64) error {
 				var keyBuf []byte // Series key buffer.
 				var name []byte
 				var tagsBuf models.Tags // Buffer for tags container.
-				var err error
+				var errs []error
 
 				ss.ForEach(func(id uint64) {
 					skey := sfile.SeriesKey(id) // Series File series key
@@ -881,22 +887,32 @@ func (s *Store) DeleteShard(shardID uint64) error {
 					}
 
 					name, tagsBuf = ParseSeriesKeyInto(skey, tagsBuf)
+					keyBuf = keyBuf[:0]
 					keyBuf = models.AppendMakeKey(keyBuf, name, tagsBuf)
-					if err = index.DropSeriesGlobal(keyBuf); err != nil {
-						return
+					if tmpErr := index.DropSeriesGlobal(keyBuf); tmpErr != nil {
+						sfile.Logger.Error(
+							"cannot drop series",
+							zap.Uint64("series_id", id),
+							zap.String("key", string(keyBuf)),
+							zap.Error(tmpErr))
+						errs = append(errs, tmpErr)
 					}
 				})
-
-				if err != nil {
-					return err
+				if len(errs) != 0 {
+					return errors.Join(errs...)
 				}
 			}
 
 			ss.ForEach(func(id uint64) {
-				sfile.DeleteSeriesID(id)
+				if err := sfile.DeleteSeriesID(id); err != nil {
+					sfile.Logger.Error(
+						"cannot delete series in shard",
+						zap.Uint64("series_id", id),
+						zap.Uint64("shard_id", shardID),
+						zap.Error(err))
+				}
 			})
 		}
-
 	}
 
 	// enter the epoch tracker
@@ -916,9 +932,13 @@ func (s *Store) DeleteShard(shardID uint64) error {
 	// Remove the on-disk shard data.
 	if err := os.RemoveAll(sh.path); err != nil {
 		return err
+	} else if err = os.RemoveAll(sh.walPath); err != nil {
+		return err
+	} else {
+		// Remove index type from the database on success
+		s.databases[db].removeIndexType(sh.IndexType())
+		return nil
 	}
-
-	return os.RemoveAll(sh.walPath)
 }
 
 // DeleteDatabase will close all shards associated with a database and remove the directory and files from disk.