The user session has the same life cycle as the public key MN_Pub, whose life period is specified by the CA server and signed in the proxy credential.
According to the user accessing right to the slave nodes, the master node creates a list of all the available slave nodes for the current user instance. In the following operations, the master node will only distribute jobs/tasks to the slave nodes in the list. This mechanism ensures that only the slave nodes that can be accessed by the user with SSH are provided to the user, so that abusing or misusing of the resources in G-Hadoop can be avoided.
Similar to the master node, the slave nodes must also make sure that the master node is not a fake but the real master node that is authenticated by the CA server. Therefore, the authentication information of the master node has to be prepared as well.