From 588bab2a1019af46a7ae9d2617a8b29bc0aeef0d Mon Sep 17 00:00:00 2001
From: TommyLike <tommylikehu@gmail.com>
Date: Thu, 21 Sep 2017 14:33:43 +0800
Subject: [PATCH] Support create volume from backup

This spec proposes support create volume
from backup.

Change-Id: Ief8487b3b41993651bbdb6da89983cc5923c0335
Partial-Implements: bp support-create-volume-from-backup
---
 specs/queens/create-volume-from-backup.rst | 165 +++++++++++++++++++++
 1 file changed, 165 insertions(+)
 create mode 100644 specs/queens/create-volume-from-backup.rst

diff --git a/specs/queens/create-volume-from-backup.rst b/specs/queens/create-volume-from-backup.rst
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+..
+ This work is licensed under a Creative Commons Attribution 3.0 Unported
+ License.
+
+ http://creativecommons.org/licenses/by/3.0/legalcode
+
+=================================
+Support create volume from backup
+=================================
+
+https://blueprints.launchpad.net/cinder/+spec/support-create-volume-from-backup
+
+
+This blueprint proposes support for creating a volume from backup.
+
+Problem description
+===================
+
+Cinder has supported create volume from volume, snapshot and image.
+But when considering create volume from backup, users have to create a
+new volume first and then restore the volume with backup. Although
+we can restore backup without volume id, in that case Cinder will
+create a new volume in the background, but we still have some issues
+because we don't have any access to control the volume's az, volume
+type, size and many other attributes.
+
+Use Cases
+=========
+
+User can directly create volume from backup rather than create a new volume
+and then restore it.
+
+Proposed change
+===============
+
+This spec proposes to support create volume from backup, after this change
+users can directly create a new volume with backup id as below:
+
+.. code-block:: bash
+
+    $ cinder create [size] --backup-id <id> [other_options]
+
+Volume's size is equal to the backup's original volume size if size
+option is omitted.
+
+Since we already introduced the generic backup implementation `[1]`_ for our
+existing volume drivers, it makes sense to add this ability to our volume
+drivers, so when create volume from backup, the request will be scheduled
+to the volume backend as normal, and first we would try the vendor-specific
+``create_volume_from_backup`` method as below:
+
+.. code-block:: python
+
+    def create_volume_from_backup(self, volume, backup):
+        """Creates a volume from a backup."""
+
+        raise NotImplementedError()
+
+If the driver reports ``NotImplemented`` or ``NotSupported``, Cinder will
+directly create the raw volume at the backend and then schedule the request
+to the backup service to restore the volume with backup.
+
+One of the differences between creating volume from snapshot and
+creating volume from backup is the latter could be time consuming, so we need
+to update the backup's status to prevent possible usages by other requests.
+For instance, when creating volume from backup the possible status for volume
+and backup are::
+
+    1. Volume: creating, available, error
+    2. Backup: restoring, available, error
+
+**Note**: We will use 'creating' instead of 'restoring-backup' for the
+volume's transition status here in order not to expose the creating detail.
+
+Alternatives
+------------
+
+Keep using current restore API or create and restore mechanism to cover
+this use case.
+
+Data model impact
+-----------------
+
+None
+
+REST API impact
+---------------
+
+Microversion bump is required for this change.
+
+Cinder-client impact
+--------------------
+
+Cinder-client will be updated to support create volume from backup.
+
+Security impact
+---------------
+
+None
+
+Notifications impact
+--------------------
+
+None
+
+Other end user impact
+---------------------
+
+None
+
+Performance Impact
+------------------
+
+When creating a volume from backup and the vendor-specific method does
+not exist, the creation process could take a little longer than
+a typical creation due to the restore action.
+
+Other deployer impact
+---------------------
+
+None
+
+Developer impact
+----------------
+
+None
+
+Implementation
+==============
+
+Assignee(s)
+-----------
+
+Primary assignee:
+
+  1. luqitao (qtlu@fiberhome.com)
+  2. tommylikehu(tommylikehu@gmail.com)
+
+Work Items
+----------
+
+* Support create volume from backup in Cinder.
+* Add related unit testcases.
+* Add related tempest testcase.
+* Update cinder-client and OSC.
+
+Dependencies
+============
+
+Depends on generic backup implementation `[4]`_
+
+Testing
+=======
+
+* Add unit tests to cover creating volume from backup.
+
+Documentation Impact
+====================
+
+Both API documentation and CLI documentation should be updated.
+
+References
+==========
+
+* _`[1]`: https://github.com/openstack/cinder-specs/blob/master/specs/queens/generic-backup-implementation.rst