taskA                                                                              
                                                                                                                 
                                                                                                                 
                                                                        data                                     
                                                                                                                 
                                                                                                                 
                                                                                                         NG      
                                            check                                                                
                                                                                                                 
                                                                        OK                                       
                                                                                                                 
                                                                                                                 
                                                                                                                 
                                                                                                                 
                                                                                                                 
                                        retry?                                                               true
                                                                                                                 
                                                                        false