docs: private boolean isRunningOutOfMemory() {
      StorageLevel level = raft.getStorage().storageLevel();
      if (level == StorageLevel.MEMORY || level == StorageLevel.MAPPED) {
        long freeMemory = raft.getStorage().statistics().getFreeMemory();
        long totalMemory = raft.getStorage().statistics().getTotalMemory();
        if (freeMemory > 0 && totalMemory > 0) {
          return freeMemory / (double) totalMemory < raft.getStorage().freeMemoryBuffer();
        }
      }
      return false;
    }