watcher-specs/specs/pike/implemented/cinder-model-integration.rst

Integrate storage (cinder) information in the model

https://blueprints.launchpad.net/watcher/+spec/cinder-model-integration

Problem description

As of now, Watcher only provides compute data model. Watcher needs storage data model for optimizing storage provided by Cinder.

Use Cases

• As a developer, I want to develop storage optimization strategy using storage data model.
• As as developer, I want to develop zone migration strategy using storage data model.

Proposed change

This spec adds storage data model separate from compute data model. Since Cinder backend has many pools, physical layer composed of backends and it's pools. Backend information can be retrieved by python-cinderclient Service resource. The model has host, zone, status, and state attributes of Service resource. For using Multi backends feature, volume type is also needed. Volume type information can be retrieved by python-cinderclient VolumeType resource.

Pool information can be retrieved by python-cinderclient Pool resource. The model has name, total_volumes, total_capacity_gb, free_capacity_gb and provisioned_capacity_gb and allocated_capacity_gb attributes of Pool resource. Virtual_fee is also element of the model which is not retrieved by python-cinderclient, but retrieved from cinder notification.

Virtual layer is Cinder volume. Volume information can be retrieved by python-cinderclient Volume resource. The model has id, name, size, status, attachements, snapshot_id, project_id and metadata attributes of Volume resource.

In order to maintain consistency of the model, notification endpoint to consume all needed cinder notifications will be added:

CapacityNotificationEndpoint

This consumes the notification emitted in _publish_service_capabilities method periodically in cinder/manager.py from cinder-scheduler service.

Payload is defined as return value of _usage_from_capacity method in cinder.volume.utils.py.

Filter_rule is publisher_id equals r'capacity.*' and event_type equals 'capacity_pool'.

This endpoint updates pool information:

pool element	notification payload
name	name_to_id
total_volumes	None
total_capacity_gb	total
free_capacity_gb	free
provisioned_capacity_gb	provisioned
allocated_capacity_gb	allocated
virtual_free	virtual_free

Total_volumes is not included in notification payload so that it is calculated when updating pool information.

Notifications for updating volume information are emitted in cinder/volume/manager.py from cinder-volume service. Payload is defined as return value of _usage_from_volume method in cinder.volume.utils.py.

VolumeCreateEnd

Filter_rule is publisher_id equals r'volume.*' and event_type equals 'volume.create.end'.

This endpoint creates an element of virtual layer under the pool element with the condition that host included in publisher_id equals pool name:

volume element	notification payload
id	volume_id
name	display_name
size	size
status	status
attachements	volume_attachment
snapshot_id	snapshot_id
project_id	tenant_id
metadata	volume_metadata

VolumeDeleteEnd

Filter_rule is publisher_id equals r'volume.*' and event_type equals 'volume.delete.end'.

This endpoint deletes the element of virtual layer with the condition that volume_id equals id.

VolumeUpdateEnd

Filter_rule is publisher_id equals r'volume.*' and event_type equals 'volume.update.end'.

This endpoint updates the element of virtual layer with the condition that volume_id equals id:

volume element	notification payload
name	display_name
size	size
status	status
attachements	volume_attachment
snapshot_id	snapshot_id
project_id	tenant_id
metadata	volume_metadata

VolumeAttachEnd

Filter_rule is publisher_id equals r'volume.*' and event_type equals 'volume.attach.end'.

This endpoint updates the element of virtual layer with the condition that volume_id equals id. The attributes updating are the same as VolumeUpdateEnd.

VolumeDetachEnd

filter_rule is publisher_id equals r'volume.*' and event_type equals 'volume.detach.end'.

This endpoint updates the element of virtual layer with the condition that volume_id equals id. The attributes updating are the same as VolumeUpdateEnd.

VolumeResizeEnd

Filter_rule is publisher_id equals r'volume.*' and event_type equals 'volume.resize.end'.

This endpoint updates the element of virtual layer with the condition that volume_id equals id. The attributes updating are the same as VolumeUpdateEnd.

Alternatives

None

Data model impact

None

REST API impact

None

Security impact

None

Notifications impact

Notification endpoint to consume cinder notifications will be added.

Other end user impact

None

Performance Impact

Watcher stores data model in memory. Watcher-decision-engine may need more physical memory.

Other deployer impact

The following is added in setup.cfg.

[entry_points]
watcher_cluster_data_model_collectors =
    storage = watcher.decision_engine.model.collector.cinder:CinderClusterDataModelCollector

Developer impact

None

Implementation

Assignee(s)

Primary assignee:

<nakamura-h>

Other contributors:

<None>

Work Items

• Add storage data model
• Add storage data model entry point in setup.cfg
• Add _storage_model instance variable and storage_model method with property decorator to BaseStrategy class
• Add notification endpoint for updating storage deta model

Dependencies

None

Testing

Unit tests should be updated.

Documentation Impact

Architecture documentation will be updated.

References

• https://blueprints.launchpad.net/watcher/+spec/zone-migration-strategy

History

None