From d695469c1136c6ec5d11b3aef3cebe14b3eaf25f Mon Sep 17 00:00:00 2001
From: wanghao <wanghao749@huawei.com>
Date: Mon, 23 May 2016 18:09:20 +0800
Subject: [PATCH] Transfer snapshots with volumes

This feature will change Cinder to transfer
snapshots with volumes at the same time by default.
If user don't want transfer snapshots, they could use
optional argument '--no-snapshots'.

APIImpact
Add an optional argument '--no-snapshots' in transfer API.

Change-Id: I287209404a31df91586bbe6bb86daed5c9a7f884
Implements: blueprint transfer-snps-with-vols
---
 .../transfer-snapshots-with-volumes.rst       | 161 ++++++++++++++++++
 1 file changed, 161 insertions(+)
 create mode 100644 specs/queens/transfer-snapshots-with-volumes.rst

diff --git a/specs/queens/transfer-snapshots-with-volumes.rst b/specs/queens/transfer-snapshots-with-volumes.rst
new file mode 100644
index 00000000..943ff91e
--- /dev/null
+++ b/specs/queens/transfer-snapshots-with-volumes.rst
@@ -0,0 +1,161 @@
+..
+ This work is licensed under a Creative Commons Attribution 3.0 Unported
+ License.
+
+ http://creativecommons.org/licenses/by/3.0/legalcode
+
+==========================================
+Transfer snapshots with volumes
+==========================================
+
+https://blueprints.launchpad.net/cinder/+spec/transfer-snps-with-vols
+
+This spec aims to extend transfer function that can transfer snapshots
+with volumes at same time.
+
+Problem description
+===================
+
+Currently, Cinder can transfer volumes to another project's owner, but
+if this volume has snapshots before transferring, after this operation,
+new owner can't delete this volume successfully since it has snapshots.
+
+Use Cases
+=========
+
+When transferring volume with snapshots, a user will now have a choice whether
+or not to transfer those snapshots along with a volume. By default, snapshots
+are transferred, but selecting this option will allow snapshots not to be
+transferred to another project.
+Note those snapshots can be deleted by the remote user if necessary.
+
+Proposed change
+===============
+
+In normal deleting, Cinder will disallow the request since the volume has
+snapshots,  but unfortunately, Cinder has cascade deleting operation now,
+the request will be passed down to driver, some driver will raise
+exception since snapshot is still existing. So it also should be changed in
+cascade deletion process.
+
+* Add an optional argument "--no-snapshots" in transfer API and CLI. If user
+  didn't specify it, cinder will transfer snapshots that a volume has by
+  default.
+* Add a new field in transfer DB model to record this option.
+* Update snapshot's information in DB like user id, project id, etc.
+* Check if the volume still has some snapshots in other project when cascade
+  deleting.
+
+
+Alternatives
+------------
+
+Another option is cinder transfer the snapshots if user specifies an option
+argument '--with-snapshots'.
+
+This option can be minimal with the change, in order to make the client code
+more simple.
+
+Data model impact
+-----------------
+
+Add a new field "with_snapshots(boolean)" in transfer model.
+
+
+REST API impact
+---------------
+
+*New microversion in Cinder API.
+
+*Add an optional argumet "no_snapshots"::
+
+  POST /v3/{project_id}/os-volume-transfer
+  RESP BODY: {"transfer": {
+                           ...
+                           no_snapshots: [True/False],
+                          }
+             }
+
+
+Security impact
+---------------
+
+If users didn't transfer snapshots with volume, there could be kind of
+security impact that remote users may be able to act upon the untransferred
+snapshots. For example, by leveraging COW, that remote user can change the
+snapshot size in backend.
+
+Notifications impact
+--------------------
+
+Add 'with_snapshots' information to transfer notificaiton.
+
+Other end user impact
+---------------------
+
+None
+
+Performance Impact
+------------------
+
+There could be a db performance issue if a lot of snapshots associated with a
+given volume since cinder need to change those snapshots' project id, user id,
+etc.
+
+Other deployer impact
+---------------------
+
+None
+
+
+Developer impact
+----------------
+
+Drivers that implement some form of volume ownership tracking on
+the backend will need to be fixed to track this change too.
+
+
+Implementation
+==============
+
+Assignee(s)
+-----------
+
+Primary assignee:
+  wanghao<sxmatch1986@gmail.com>
+
+Other contributors:
+  None
+
+Work Items
+----------
+
+* Implement feature in Cinder tree.
+* Update cinderclient to support this functionality.
+* Add change to API doc.
+
+
+Dependencies
+============
+
+None
+
+
+Testing
+=======
+
+Both unit and Tempest tests are needed to be created to cover the code change.
+
+
+Documentation Impact
+====================
+
+The cinder API documention will need to be updated to reflect the REST
+API changes.
+
+Devref entry on the volume transfer driver entry point should be created.
+
+
+References
+==========
+None