loop over all instances to find a free one                                                                                                                                                                                                                                                                                                              
                                                                                                                                                                                                                                                                                                                                                                                                                                      
                                                                                                                                                                                                                                                                                                                                                                                                                                      
                                                                                                                                                                                                                                                                                                                                                                                                                                      
                                                                                                                                                                                                                                                                                                                                                                                                                                      
                                                                                                                                                                                                                                                                instance exists?                                                                                                                                                      
                                                                                                                                                                                                                                                                                                                                                                                                                                      
                                                                                                                                                                                                                                                                                                                                                                                                                                      
                                                                                                                                                                                                                                                                                                         yes                                                                                                                          
                                                                                                                                                                                                                                                                                                                                                     free?                                                                            
                                                                                                                                                                                                                                                                                                                                                                                                                                      
                                                                                                                                                                                                                                                                                                                                                                                                                                      
                                                                                                                                                                                                                                                                                                                                                                                                                                      
                                                      reserve this instance                                                                                                                                                                                                                                                                                                                                          get next instance