[api-ref]Volume status management during migration

[OpenStack Infra]

https://review.openstack.org/186312
commit 21bc0537e04c666f99d7ee0d5eca6fcb5e589523
Author: Vincent Hou <email address hidden>
Date: Thu May 28 11:18:09 2015 +0800

    Volume status management during migration

    This patch proposes a new implementation for the status and
    the migration_status for volumes.

    * The initial migration_status is None, meaning no migration has been
    done; Migration_status 'error' means the previous migration failed.
    Migration_status 'success' means the previous migration succeeded.

    * If the key 'lock_volume' is set to True from the request, the volume
    status should be set to 'maintenance' during migration and goes
    back to its original status after migration. Otherwise, if the
    key 'lock_volume' is set to False, the volume status will remain the
    same as its original status. The default value for lock_volume is
    False and it applies to the available volume.

    * From the REST's perspectives, all the create, update and delete
    actions are not allowed if the volume is in 'maintenance', because
    it means the volume is out of service. If it is not in maintenance
    mode, the migration can be interrupted if other requests are
    issued, e.g. attach. For the termination of migration, another
    patch will target to resolve it.

    DocImpact
    APIImpact The key 'lock_volume' has been added into the API,
    telling the volume to change the status to 'maintenance' or not.
    The migration_status has been added into results returned
    from volume list command, if the request is from an admin.

    Change-Id: Ia86421f2d6fce61dcfeb073f8e7b9c9dde517373
    Partial-implements: blueprint migration-improvement

[Lana (loquacity)]

This doesn't appear to have openstack-manuals impact. Please reopen with more info if you disagree.