code: public void onError(Throwable cause) {
      if (cause instanceof StatusRuntimeException
          && ((StatusRuntimeException) cause).getStatus().getCode() == Status.Code.CANCELLED) {
        // Cancellation is already handled.
        return;
      }
      mSerializingExecutor.execute(() -> {
        LogUtils.warnWithException(LOG, "Exception thrown while handling write request {}",
            mContext == null ? "unknown" : mContext.getRequest(), cause);
        abort(new Error(AlluxioStatusException.fromThrowable(cause), false));
      });
    }
docs: Handles errors from the request.
  
  @param cause the exception