prune in batches to avoid writer starvation

server/prune.go

@@ -8,41 +8,55 @@ import (
 	"github.com/gofrs/uuid"
 )
 
+const batchSize = 10000
+
 func (s Server) Prune(cutoffTime time.Time) (err error) {
-	return bolted.SugaredWrite(s.db, func(tx bolted.SugaredWriteTx) (err error) {
-		toDelete := []string{}
-		defer func() {
-			if err == nil {
-				s.log.Info("pruned state events", "count", len(toDelete))
-			}
-		}()
-		it := tx.Iterator(eventsPath)
-		for ; !it.IsDone(); it.Next() {
-			id, err := uuid.FromString(it.GetKey())
-			if err != nil {
-				return fmt.Errorf("could not parse uuid %s: %w", it.GetKey(), err)
-			}
 
-			ts, err := uuid.TimestampFromV6(id)
-			if err != nil {
-				return fmt.Errorf("could not get uuid timestamp: %w", err)
-			}
+	eventsDeleted := true
+
+	for eventsDeleted {
+		err = bolted.SugaredWrite(s.db, func(tx bolted.SugaredWriteTx) (err error) {
+			toDelete := []string{}
+			defer func() {
+				if err == nil {
+					s.log.Info("pruned state events", "count", len(toDelete))
+				}
+			}()
+			it := tx.Iterator(eventsPath)
+			for ; !it.IsDone(); it.Next() {
+				id, err := uuid.FromString(it.GetKey())
+				if err != nil {
+					return fmt.Errorf("could not parse uuid %s: %w", it.GetKey(), err)
+				}
+
+				ts, err := uuid.TimestampFromV6(id)
+				if err != nil {
+					return fmt.Errorf("could not get uuid timestamp: %w", err)
+				}
+
+				t, err := ts.Time()
+				if err != nil {
+					return fmt.Errorf("could not get time from uuid timestamp: %w", err)
+				}
+
+				if !t.Before(cutoffTime) {
+					break
+				}
+				toDelete = append(toDelete, it.GetKey())
+
+				if len(toDelete) >= batchSize {
+					break
+				}
 
-			t, err := ts.Time()
-			if err != nil {
-				return fmt.Errorf("could not get time from uuid timestamp: %w", err)
 			}
 
-			if !t.Before(cutoffTime) {
-				break
+			eventsDeleted = len(toDelete) > 0
+			for _, id := range toDelete {
+				tx.Delete(eventsPath.Append(id))
 			}
-			toDelete = append(toDelete, it.GetKey())
-
-		}
+			return nil
+		})
+	}
 
-		for _, id := range toDelete {
-			tx.Delete(eventsPath.Append(id))
-		}
-		return nil
-	})
+	return
 }