taskA                                                                              
                                                                                                                      
                                                                                                                      
                                                                             data                                     
                                                                                                                      
                                                                                                                      
                                                 check                                                        NG      
                                                                                                                      
                                                                             OK                                       
                                                                                                                      
                                                                                                                      
                                                                                                                      
                                                                                                                      
                                                                                                                      
                                                                                                                  true
                                             retry?                                                                   
                                                                                                                      
                                                                             false