@Override
        public final FileVisitResult visitFileFailed(Path file, IOException exc) {
            collector.recordVisitFileFailed();
            return doVisitFileFailed(file, exc);
        }

        protected abstract FileVisitResult doVisitFileFailed(Path file, IOException exc);

        @Override
        public final FileVisitResult postVisitDirectory(Path dir, IOException exc) {

        }

        /**
         * unlistable directories (and maybe some locked files) will stop here
         */
        @Override
        protected FileVisitResult doVisitFileFailed(Path file, IOException exc) {
            String internedFileName = getInternedFileName(file);
            pathTracker.enter(internedFileName);
            try {