The nova.manager Module

Base Manager class.

Managers are responsible for a certain aspect of the system. It is a logical grouping of code relating to a portion of the system. In general other components should be using the manager to make changes to the components that it is responsible for.

For example, other components that need to deal with volumes in some way, should do so by calling methods on the VolumeManager instead of directly changing fields in the database. This allows us to keep all of the code relating to volumes in the same place.

We have adopted a basic strategy of Smart managers and dumb data, which means rather than attaching methods to data objects, components should call manager methods that act on the data.

Methods on managers that can be executed locally should be called directly. If a particular method must execute on a remote host, this should be done via rpc to the service that wraps the manager

Managers should be responsible for most of the db access, and non-implementation specific data. Anything implementation specific that can’t be generalized should be done by the Driver.

In general, we prefer to have one manager with multiple drivers for different implementations, but sometimes it makes sense to have multiple managers. You can think of it this way: Abstract different overall strategies at the manager level(FlatNetwork vs VlanNetwork), and different implementations at the driver level(LinuxNetDriver vs CiscoNetDriver).

Managers will often provide methods for initial setup of a host or periodic tasks to a wrapping service.

This module provides Manager, a base class for managers.

class Manager(host=None, db_driver=None, service_name='undefined')

Bases: nova.db.base.Base, nova.manager.PeriodicTasks

cleanup_host()

Hook to do cleanup work when the service shuts down.

Child classes should override this method.

init_host()

Hook to do additional manager initialization when one requests the service be started. This is called before any service record is created.

Child classes should override this method.

periodic_tasks(context, raise_on_error=False)

Tasks to be run at a periodic interval.

post_start_hook()

Hook to provide the manager the ability to do additional start-up work immediately after a service creates RPC consumers and starts ‘running’.

Child classes should override this method.

pre_start_hook()

Hook to provide the manager the ability to do additional start-up work before any RPC queues/consumers are created. This is called after other initialization has succeeded and a service record is created.

Child classes should override this method.

class PeriodicTasks

Bases: oslo_service.periodic_task.PeriodicTasks