instance_actions table should have a UniqueConstraint on instance_uuid and request_id

[Matt Riedemann]

An instance action should be unique per instance uuid and request ID. That's pointed out in the data model:

https://github.com/openstack/nova/blob/master/nova/db/sqlalchemy/models.py#L1241

"The intention is that there will only be one of these per user request. A lookup by (instance_uuid, request_id) should always return a single result."

It's also enforced in the API:

https://github.com/openstack/nova/blob/master/nova/db/sqlalchemy/api.py#L5719

def action_get_by_request_id(context, instance_uuid, request_id):
    """Get the action by request_id and given instance."""
    action = _action_get_by_request_id(context, instance_uuid, request_id)
    return action

But that is not actually enforced in the schema using a UniqueConstraint.

This is a low priority but it's technically something we should have in the data model/schema.

[Matt Riedemann (mriedem)]

Note that any database migration which adds a UniqueConstraint here would have to check for duplicates and drop them before attempting to create the constraint.

[robin (robinflx25)]

when i made a lookup in nova database;instance_actions table its showing the unique action..

1.I started the vm
2.shutoff the VM
3.again started the same VM.

Below is the entries made in the db (nova ) and in the table (instance_actions).The request_id is unique for the particular VM

instance_uuid | request_id | action |
37b1b32f-ecbd-4079-960f-80142c4a77dd | req-db08ba63-806f-4d1c-a199-3ef87ce84b0c | start |
| 37b1b32f-ecbd-4079-960f-80142c4a77dd | req-e185f9f8-b61c-4be1-baca-7a8967de68f9 | stop |
| 37b1b32f-ecbd-4079-960f-80142c4a77dd | req-92794d3c-08ef-4827-81e0-981ea28942f9 | start |

Please correct me if i am wrong.....

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/365181

[OpenStack Infra (hudson-openstack)]

Change abandoned by Michael Still (<email address hidden>) on branch: master
Review: https://review.openstack.org/365181
Reason: This patch has been sitting unchanged for more than 12 weeks. I am therefore going to abandon it to keep the review queue sane. Please feel free to restore the change if you're still working on it.

[OpenStack Infra (hudson-openstack)]

Change abandoned by Sean Dague (<email address hidden>) on branch: master
Review: https://review.openstack.org/365181
Reason: This review is > 4 weeks without comment, and is not mergable in it's current state. We are abandoning this for now. Feel free to reactivate the review by pressing the restore button and leaving a 'recheck' comment to get fresh test results.