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As was described previously, the active_model slice is primarily used to view information about the Active Models that have been bound to Nodes in the system. When a given Policy is mapped to a specific Node (based on the tags that have been applied to that node and the tags associated with that policy), a copy of that Policy instance is made and that copy is bound to that Node as an Active Model. Hanlon then uses that Active Model (and the state associated with the Node) to determine what should be done whenever that Node checks in.

The active_model CLI

The active_model CLI provides users with commands to get a list of the active_model instances in the system, get the details of a specific active_model instance, view the logs for a specific active_model instance, print an aggregate view of the logs of all of the active_model instances in the system to the shell/console being used, or remove active_model instances from the system (either one by one or all at once). The usage for the active_model CLI is as follows:

hanlon active_model [get] [all]          View all active models
hanlon active_model [get] (UUID) [logs]  View specific active model (log)
hanlon active_model logs                 Prints an aggregate view of active model logs
hanlon active_model remove (UUID)        Remove existing active model(s)
hanlon active_model --help|-h            Display this screen

The active_model RESTful API

The active_model RESTful API is provided via two resources ('/active_model' and '/active_model/{UUID}'). The operations that are supported for each of these resources are as follows:

  • GET /active_model -- used to get a summary view of all of the active_model instances in the system
  • GET /active_model/{UUID} -- used to get the details of a specific model instance (by UUID); the details returned include information about the model that is contained within that active_model instance, the node that it is bound to, and a complete log of the state-machine transitions for that node since the active_model was bound to it.
  • DELETE /active_model/{UUID} -- used to remove a specific active_model instance (by UUID), which 'unbinds' that active_model instance from the node that it was bound to; the effect of this operation is to force a reevaluation of that node against the current policy table the next time that node checks in with Hanlon (which may result in a new OS instance being installed on that node if there is a policy instance that matches that node in the current policy table)

It should be noted here that active_model instances are never created or modified by end-users (only by Hanlon), so there is no support for POST or PUT operations provided by either of these two RESTful services endpoints (nor is there support from the equivalent 'add' or 'update' operations in the active_model CLI. It should also be noted that while the CLI supports access to the active_model logs (either for all active_model instances or for a specific instance), that functionality is not supported through the RESTful API unless the RESTful API is invoked directly from the Hanlon server.