How to make a service(customer) be served more than once?

i want use Jsprit to solve vehicle routing problems on osm data, in osm data, services has topology relation, link a directed graph, that make one service may be serviced more than once, how can i make is happens in Jsprit ?

Well this is more bussiness question then algorithm. In your case there is difference between service as jsprit job, and service as order in business. So If you wanna visit customer twice, you need two jobs (services). Then you can bind them through Order entity for business purpose.