1. A method for acquiring a cost between nodes, comprising: receiving, by a first server, a first cost request message from a client, wherein the first cost request message comprises a first source node list, a first candidate node list, and a cost type; calculating a cost between each source node in the first source node list and each candidate node in the first candidate node list according to the cost type; sending a second cost request message to a second server when the first server fails to complete the calculation of the cost between each source node in the first source node list and each candidate node in the first candidate node list, wherein the second cost request message comprises a second source node list, a second candidate node list, and the cost type; receiving a second cost response message from the second server, wherein the second cost response message comprises a second cost list, and the second cost list comprises a source node in the second source node list, a candidate node in the second candidate node list, and a corresponding cost; and calculating a first cost list according to the second cost list, and sending a first cost response message to the client, wherein the first cost response message comprises the first cost list.