private void unblockMessage() {
    for (int i = 0; i < serverCount(); i++) {
      BlockTpcCommunicationSpi commSpi = commSpi(grid(i));

      commSpi.unblockMessage();
    }
  }
  /** @param clazz Message class. */
  private void blockMessage(Class<?> clazz) {
    for (int i = 0; i < serverCount(); i++) {
      BlockTpcCommunicationSpi commSpi = commSpi(grid(i));

      commSpi.blockMessage(clazz);
    }
  }