Surya Seetharaman d693d4c06c Support power state change callbacks to nova using ksa_adapter

Add power state change callbacks of an instance to nova by
performing API requests. Whenever there is a change in the
power state of a physical instance (example a "power on"
or "power off" IPMI command is issued or the periodic
``_sync_power_states`` task detects a change in power state)
ironic will create and send a ``power-update`` external event
to nova using which nova will update the power state of the
instance in its database. By conveying the power state changes
to nova, ironic becomes the source of truth thus preventing
nova from forcing wrong power states on the instance during
the nova-ironic periodic sync. It also adds the possibility of
bringing up/down a physical instance through the ironic API
even if it was put down/up through the nova API.

Note that ironic only sends requests to nova if the target
power state is either "power on" or "power off". Other error
states will be ignored. In cases where the power state change
is originally coming from nova, the event will still be
created and sent to nova and on the nova side it will be a
no-op with a debug log saying the node is already powering on/off.

NOTE: Although an exclusive lock (task_manager.upgrade_lock()
method) is used when calling the nova API to send events,
there can still be a race condition if the nova-ironic power sync
happens to happen a nano-second before the power state change
event is received from ironic in which case the nova state will
be forced on the node.

Credit for introducing ksa adapter: Eric Fried <openstack@fried.cc>
Depends-On: https://review.opendev.org/#/c/645611/
Part of blueprint nova-support-instance-power-update
Story: 2004969
Task: 29424

Change-Id: I6d105524e1645d9a40dfeae2850c33cf2d110826

2019-08-12 19:29:57 +02:00

4.1 KiB

Raw Blame History

Power Sync with the Compute Service

Baremetal Power Sync

Each Baremetal conductor process runs a periodic task which synchronizes the power state of the nodes between its database and the actual hardware. If the value of the :oslo.configconductor.force_power_state_during_sync option is set to true the power state in the database will be forced on the hardware and if it is set to false the hardware state will be forced on the database. If this periodic task is enabled, it runs at an interval defined by the :oslo.configconductor.sync_power_state_interval config option for those nodes which are not in maintenance.

Compute-Baremetal Power Sync

Each nova-compute process in the Compute service runs a periodic task which synchronizes the power state of servers between its database and the compute driver. If enabled, it runs at an interval defined by the sync_power_state_interval config option on the nova-compute process. In case of the compute driver being baremetal driver, this sync will happen between the databases of the compute and baremetal services. Since the sync happens on the nova-compute process, the state in the compute database will be forced on the baremetal database in case of inconsistencies. Hence a node which was put down using the compute service API cannot be brought up through the baremetal service API since the power sync task will regard the compute service's knowledge of the power state as the source of truth. In order to get around this disadvantage of the compute-baremetal power sync, baremetal service does power state change callbacks to the compute service using external events.

Power State Change Callbacks to the Compute Service

Whenever the Baremetal service changes the power state of a node, it can issue a notification to the Compute service. The Compute service will consume this notification and update the power state of the instance in its database. By conveying all the power state changes to the compute service, the baremetal service becomes the source of truth thus preventing the compute service from forcing wrong power states on the physical instance during the compute-baremetal power sync. It also adds the possibility of bringing up/down a physical instance through the baremetal service API even if it was put down/up through the compute service API.

This change requires the :oslo.confignova section and the necessary authentication options like the :oslo.confignova.auth_url to be defined in the configuration file of the baremetal service. If it is not configured the baremetal service will not be able to send notifications to the compute service and it will fall back to the behaviour of the compute service forcing power states on the baremetal service during the power sync. See :oslo.confignova group for more details on the available config options.

In case of baremetal stand alone deployments where there is no compute service running, the :oslo.confignova.send_power_notifications config option should be set to False to disable power state change callbacks to the compute service.

Note

The baremetal service sends notifications to the compute service only if the target power state is power on or power off. Other error and None states will be ignored. In situations where the power state change is originally coming from the compute service, the notification will still be sent by the baremetal service and it will be a no-op on the compute service side with a debug log stating the node is already powering on/off.