Improvement to query consistency group detail

https://blueprints.launchpad.net/cinder/+spec/improvement-to-query-consistency-group-detail

Return the volume id list if they exist in CG when querying CG detail.

Problem description

Currently, querying consistency group detail will not return list of volumes ids that exist in this CG, end users don’t know how many and which volumes are in it. They must query the volume detail one by one to get the CG’s id and form the list of volume ids. It’s very inconvenient to user experience.

Use Cases

After adding volumes to a consistency group, end user wants to know how many and which volumes are in a CG before they decide to make CG snapshot. According to this feature, they can get this information easily by querying consistency group detail, and make further adjustment, like adding more volumes, or remove some volumes from this consistency group.

Proposed change

1.Add volume id list into response body of querying a consistency group detail if user wants those volume’s information.

2.Add group_id query filter to /volumes to get a list of volumes in a CG. For example “cinder list –group-id <uuid of CG>”.

NOTE: Since we’re working on Generic Volume Group[1], to avoid unnecessary code migration later, we will implement the ‘group_id’ query filter first, and after Generic Volume Group is merged, we will implement the #1 way dependent on the Generic Group spec.

Alternatives

None

Data model impact

For performance impact, if we want to add index to consistencygroup_id column, there is data model impact.

REST API impact

  • Add volume id list into response body of querying a CG detail if specifying the argument ‘list_volume=True’, this will be dependent on the Generic Group spec now, so just leave a example here:

GET /v3/{project_id}/consistencygroups/{consistency_group_id}?list_volume=True

RESP BODY:

{"consistencygroup": {"status": "XXX",
                      "description": "XXX",
                      ...,
                      "volume_list":['volume_id1',
                                     ...,
                                     'volume_idn']
                      }
}

  • Add a filter “group_id=xxx” in URL of querying volume list/detail:

GET /v3/{project_id}/volumes?group_id=XXX

Security impact

None

Notifications impact

None.

Other end user impact

None

Performance Impact

There is no performance impact if user is NOT using ‘list_volume=True’. We just need to consider to add a additional DB query to get all volume ids which have same CG id. So the performance impact should be small with ‘list_volume=True’. If considering large scale volumes, we can add index to consistencygroup_id column of volume table to reduce performance impact.

Other deployer impact

None

Developer impact

None

Implementation

Assignee(s)

Primary assignee:

wanghao<wanghao749@huawei.com>

Work Items

  • Implement code in db query and add list to response body.

  • Update cinderclient to support this function.

  • Add change to API doc.

Dependencies

None

Testing

Both unit and Tempest tests need to be created to cover the code change that mentioned in “Proposed change”.

Documentation Impact

  1. The cinder API documentation will need to be updated to reflect the REST API changes.

References

[1]https://review.openstack.org/#/c/303893/