Allow unshelve to a specific host

https://blueprints.launchpad.net/nova/+spec/unshelve-to-host

This blueprint proposes to allow administrator to specify host to unshelve a shelved offloaded server.

Problem description

Currently, an instance can only be unshelved to a specific availability zone. The proposal is to extend the unshelve behavior allowing an instance to be unshelved to a specific host.

Use Cases

As a PROJECT_ADMIN, I want to specify a destination host when executing unshelve on a shelved-offloaded instance.

Proposed change

Add a new microversion to extend the unshelve API behavior to support a specific destination host.

Add host attribute to POST /server/uuid/action for unshelve request body.

Add 2 checks:

• Ensure the user is a PROJECT_ADMIN.

• Ensure the instance state is shelved_offloaded.

With the introduction of the new microversion, change the scheduling and request specification (reqspec) behaviors of the unshelve API.

Current behavior:

Boot	Unshelve after offload	Result
No AZ	No AZ	Free scheduling, reqspec.AZ kept None
No AZ	AZ	Schedule in the AZ, update reqspec.AZ to the requested one
With AZ	No AZ	Schedule in original AZ, keep reqspec pointing that AZ
With AZ	AZ	Schedule to the new AZ, update the reqspec.AZ to the new AZ

Proposed new behavior:

Boot	Unshelve after offload AZ	Host	Result
No AZ	No AZ or AZ=null	No	Free scheduling, reqspec.AZ=None
No AZ	No AZ or AZ=null	Host1	Schedule to host1, reqspec.AZ=None
No AZ	AZ=”AZ1”	No	Schedule to AZ1, reqspec.AZ=”AZ1”
No AZ	AZ=”AZ1”	Host1	Verify that host1 in AZ1, or (3). Schedule to host1, reqspec.AZ=”AZ1”
AZ1	No AZ	No	Schedule to AZ1, reqspec.AZ=”AZ1”
AZ1	AZ=null	No	Free scheduling, reqspec.AZ=None
AZ1	No AZ	Host1	If host1 is in AZ1, then schedule to host1, reqspec.AZ=”AZ1”, otherwise reject the request (1)
AZ1	AZ=null	Host1	Schedule to host1, reqspec.AZ=None
AZ1	AZ=”AZ2”	No	Schedule to AZ2, reqspec.AZ=”AZ2”
AZ1	AZ=”AZ2”	Host1	If host1 in AZ2 then schedule to host1, reqspec.AZ=”AZ2”, otherwise reject (1)

1. Check at the api and return an error.

Alternatives

The current proposal rejects unshelve to a specific host if the instance state is not shelved_offloaded. Alternatively, a request to unshelve to a specific host would change the instance state to shelved_offloaded automatically. So the user would not have to worry about the initial instance state.

Data model impact

None

REST API impact

Change the validation schema allowing availability_zone=null and host. An error in schema validation will raise a HTTP400.

Ensure the instance state is shelved_offloaded. An error in such case will rise a HTTP409.

Starting from the new API microversion, the POST /servers/{server_id}/action API can be called with the following body:

• {“unshelve”: null} (Keep compatibility with previous microversions)

or

• {“unshelve”: {“availability_zone”: <string>}}

• {“unshelve”: {“availability_zone”: null}} (Unpin availability zone)

• {“unshelve”: {“host”: <fqdn>}}

• {“unshelve”: {“availability_zone”: <string>, “host”: <fqdn>}}

• {“unshelve”: {“availability_zone”: null, “host”: <fqdn>}}

Everything else is not allowed, examples:

• {“unshelve”: {}}

• {“unshelve”: {“host”: <fqdn>, “host”: <fqdn>}}

• {“unshelve”: {“foo”: <string>}}

Security impact

None

Notifications impact

None

Other end user impact

The python-openstackclient will be updated and will provide support for the new microversion.

A new switch --unpin-az will be introduced to the unshelve command allowing PROJECT_ADMIN to remove the availability zone constraint of a server.

The python-novaclient will just be extended with the python helper functions.

Performance Impact

None

Other deployer impact

None

Developer impact

None

Upgrade impact

None

Implementation

Assignee(s)

Primary assignee:

Uggla (rene.ribaud)

Feature Liaison

Feature liaison:

sbauza

Work Items

• Add a new microversion to the unshelve to a specific host (unshelve Action) API

• Add related tests

Dependencies

None

Testing

• Add related unit tests

• Add related functional tests

• Add a tempest test

Documentation Impact

The API reference and the unshelve documentation will be updated to explain the new behavior introduced by the new microversion.

References

None

History

Revisions

Release Name	Description
Zed	Introduced