If I understand correctly I can't open required snapshot immediately
if I know only its namespace.
I need to get the whole list of snapshots first and then find mine
using its namespace.
After that I want to redirect the opened image to my snapshot.
On Wed, Jan 11, 2017 at 4:18 PM, Jason Dillaman <jdillama@xxxxxxxxxx> wrote:
> You can specify the snapshot at image open as well. There is no need to refresh.
>
> On Wed, Jan 11, 2017 at 7:14 PM, Victor Denisov <vdenisov@xxxxxxxxxxxx> wrote:
>> Can I open an image and then redirect it to one of its snapshots?
>>
>> I see that there is a snap_set method.
>> Do I understand correctly that I need to:
>> open the image
>> invoke snap_set method
>> invoke refresh method
>>
>> Thanks in advance.
>> V.
>>
>> On Wed, Jan 4, 2017 at 10:39 AM, Victor Denisov <vdenisov@xxxxxxxxxxxx> wrote:
>>> I understood. Thanks!
>>>
>>> On Wed, Jan 4, 2017 at 10:34 AM, Jason Dillaman <jdillama@xxxxxxxxxx> wrote:
>>>> The loop isn't that big of a deal -- but you could eliminate it
>>>> entirely if you just index the in-memory snapshot table via the
>>>> SnapshotNamespace variant instead of just indexing snapshots by name
>>>> (e.g. ImageCtx::snap_ids key switches from a string to a namespace).
>>>> This would be required anyway since you might otherwise have duplicate
>>>> names between namespaces.
>>>>
>>>> On Wed, Jan 4, 2017 at 1:29 PM, Victor Denisov <vdenisov@xxxxxxxxxxxx> wrote:
>>>>> It looks like next CDM is only next month. Let's try to figure it out in email.
>>>>>
>>>>>> Since you know which images are linked to the group and you know which
>>>>>> snapshots are in the group and which group snapshots are in the image,
>>>>>> you can reconcile any issues using the details in the
>>>>>> GroupSnapshotNamespace -- there shouldn't be any need to depend on the
>>>>>> actual snapshot name (it could technically just be a randomly assigned
>>>>>> UUID).
>>>>>
>>>>> Let's say I have a consistency group and a snapshot of this group: CG
>>>>> and CGSNAP.
>>>>> Images in this snapshot I'll define as:
>>>>> CG.images[0] - image1
>>>>> CG.images[1] - image2
>>>>> CG.images[2] - image3
>>>>>
>>>>> Image snapshots in cg snapshot will be:
>>>>> CG.CGSNAP.snaps[0] - reference to snapshot of image 1
>>>>> CG.CGSNAP.snaps[1] - reference to snapshot of image 2
>>>>>
>>>>> Imagine that this snapshot was created, but wasn't finalized.
>>>>> CG.CGSNAP.state == PENDING.
>>>>> CG.CGSNAP.snaps.length == 0;
>>>>> I'll be writing in pseudo code.
>>>>>
>>>>> Now, let's say we want to remove this pending CGSNAP. This is the code
>>>>> how it's currently implemented:
>>>>>
>>>>> for (image: CG.images) {
>>>>> snap_name = image.id + "_" + CG.CGSNAP.id + "_" + CG.id // This name
>>>>> is unique because of uniqueness of the tuple (image.id, CG.CGSNAP.id,
>>>>> CG.id)
>>>>> remove_image_snapshot(snap_name);
>>>>> }
>>>>> remove_cg_snap(CGSNAP);
>>>>>
>>>>> However, if we don't rely on the name then this is how I envision the code:
>>>>>
>>>>> for (image: CG.images) {
>>>>> for (snap: image.snaps) {
>>>>> if (snap.namespace.cg_id == CG.id && snap.namespace.cg_snap_id ==
>>>>> CG.CGSNAP.id) { // this is our snapshot
>>>>> remove_image_snapshot(snap.name);
>>>>> }
>>>>> }
>>>>> }
>>>>> remove_cg_snap(CGSNAP);
>>>>>
>>>>> In this solution I don't like the internal loop.
>>>>> What do you think?
>>>>>
>>>>> Thanks,
>>>>> Victor.
>>>>>
>>>>>
>>>>> On Tue, Jan 3, 2017 at 6:56 PM, Jason Dillaman <jdillama@xxxxxxxxxx> wrote:
>>>>>> After starting the process of creating a group snapshot, you will
>>>>>> already have all the necessary data for the group snapshot namespace
>>>>>> [1] (group pool, group id, and group snapshot id) and the group
>>>>>> snapshot should be persistently recorded to disk as
>>>>>> GROUP_SNAPSHOT_STATE_PENDING.
>>>>>>
>>>>>> Looking at the snapshot create state machine [2], I don't see any
>>>>>> place that a crash (or similar failure) would matter before the actual
>>>>>> image snapshot record is created atomically. You would pass the fully
>>>>>> populated GroupSnapshotNamespace to snap_create, and if the snapshot
>>>>>> is created, it's linked to the group via that namespace and any
>>>>>> failures afterwards don't matter since they are linked -- if the
>>>>>> snapshot fails to be created, it isn't linked to the group but the
>>>>>> snapshot doesn't exist either so there isn't anything to clean up.
>>>>>>
>>>>>> Since you know which images are linked to the group and you know which
>>>>>> snapshots are in the group and which group snapshots are in the image,
>>>>>> you can reconcile any issues using the details in the
>>>>>> GroupSnapshotNamespace -- there shouldn't be any need to depend on the
>>>>>> actual snapshot name (it could technically just be a randomly assigned
>>>>>> UUID).
>>>>>>
>>>>>> Perhaps we could talk about this at a future RBD standup meeting that
>>>>>> you are able to join (or the next CDM).
>>>>>>
>>>>>> [1] https://github.com/ceph/ceph/blob/master/src/cls/rbd/cls_rbd_types.h#L249
>>>>>> [2] https://github.com/ceph/ceph/blob/master/src/librbd/operation/SnapshotCreateRequest.h#L28
>>>>>>
>>>>>> On Tue, Jan 3, 2017 at 7:40 PM, Victor Denisov <vdenisov@xxxxxxxxxxxx> wrote:
>>>>>>> Let's say we start creating a group snapshot.
>>>>>>> We invoke async snap_create method in Operations class.
>>>>>>> When we invoke this method we provide it with the snapshot name.
>>>>>>>
>>>>>>> While we are wating for the response we can be aborted.
>>>>>>> As a result we will be able to find the exact image snapshot using only its name
>>>>>>> as this was the only information we had at the time of running
>>>>>>> snap_create method.
>>>>>>>
>>>>>>> If snap_create was successful we will be able to find the snapshot
>>>>>>> otherwise we will not.
>>>>>>> However if we allow renaming snapshots from GroupSnapshotNamespace
>>>>>>> then we may not find the snapshot even if it
>>>>>>> was created successfully.
>>>>>>>
>>>>>>> On Fri, Dec 16, 2016 at 6:53 AM, Jason Dillaman <jdillama@xxxxxxxxxx> wrote:
>>>>>>>> Can you give a little background on this specific inconsistent case
>>>>>>>> you are referring to?
>>>>>>>>
>>>>>>>> On Thu, Dec 15, 2016 at 7:05 PM, Victor Denisov <vdenisov@xxxxxxxxxxxx> wrote:
>>>>>>>>> Yes, but if image's snapshot is renamed then I'm not able to find this
>>>>>>>>> snapshot having only group's snapshot in an inconsistent state for
>>>>>>>>> example.
>>>>>>>>>
>>>>>>>>> V.
>>>>>>>>>
>>>>>>>>> On Thu, Dec 15, 2016 at 7:10 AM, Jason Dillaman <jdillama@xxxxxxxxxx> wrote:
>>>>>>>>>> I think I might be confused. When creating a group snapshot, we have
>>>>>>>>>> the ConsistencyGroupSnapshot that allows you to store the necessary
>>>>>>>>>> linkage between the image's snapshot and its associated group snapshot
>>>>>>>>>> [1]. Why not just name the image's snapshots to the same name as the
>>>>>>>>>> parent group snapshot name and search the snapshot's metadata to get
>>>>>>>>>> the linkage?
>>>>>>>>>>
>>>>>>>>>> [1] https://github.com/ceph/ceph/blob/master/src/cls/rbd/cls_rbd_types.h#L255
>>>>>>>>>>
>>>>>>>>>> On Tue, Dec 13, 2016 at 8:03 PM, Victor Denisov <vdenisov@xxxxxxxxxxxx> wrote:
>>>>>>>>>>> Jason,
>>>>>>>>>>>
>>>>>>>>>>> My current implementation of consistency group snapshot feature names
>>>>>>>>>>> image snapshots like: <group_pool>_<group_id>_<group_snap_id>
>>>>>>>>>>> I rely on this fact when I need to remove a consistency group. It's
>>>>>>>>>>> necessary because if some of image snapshots were created, but the
>>>>>>>>>>> whole group snapshot operation failed,
>>>>>>>>>>> then the only way to find those dangling image snapshots is by this name.
>>>>>>>>>>>
>>>>>>>>>>> It means that we should forbid renaming snapshots from
>>>>>>>>>>> ConsistencyGroupSnapshot namespace.
>>>>>>>>>>>
>>>>>>>>>>> Another option is to allocate image snapshot ids during the creation
>>>>>>>>>>> of group snapshot, but this requires a major rewrite of the whole
>>>>>>>>>>> process of snapshot creation for images.
>>>>>>>>>>>
>>>>>>>>>>> What is your opinion on this?
>>>>>>>>>>>
>>>>>>>>>>> Thanks,
>>>>>>>>>>> V.
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>> On Tue, Nov 1, 2016 at 8:01 AM, Jason Dillaman <jdillama@xxxxxxxxxx> wrote:
>>>>>>>>>>>> I chatted with Xing on IRC this morning re: Cinder generic groups. It
>>>>>>>>>>>> sounds like RBD will need to support preserving the image's
>>>>>>>>>>>> consistency group snapshots even if the image is removed from the
>>>>>>>>>>>> group. In the OpenStack case, you won't have to worry about the image
>>>>>>>>>>>> being deleted while it still has associated group snapshots.
>>>>>>>>>>>>
>>>>>>>>>>>> We will also want to support being able to clone child images from a
>>>>>>>>>>>> group snapshot to ensure that we can thin provision new groups volumes
>>>>>>>>>>>> when creating a new group from a group snapshot. This means that the
>>>>>>>>>>>> group snapshots should be able to be protected/unprotected just like
>>>>>>>>>>>> standard user snapshots.
>>>>>>>>>>>>
>>>>>>>>>>>> On Mon, Oct 31, 2016 at 9:07 AM, Jason Dillaman <jdillama@xxxxxxxxxx> wrote:
>>>>>>>>>>>>> Looking at the Cinder codebase, I don't see any such restriction that
>>>>>>>>>>>>> would prevent you from removing a volume from a consistency group that
>>>>>>>>>>>>> has associated snapshots. I would double-check on the OpenStack
>>>>>>>>>>>>> development mailing list if this is correct and is the intent. Worst
>>>>>>>>>>>>> case, the RBD driver could raise an exception if there are still
>>>>>>>>>>>>> consistency group snapshots associated to the image.
>>>>>>>>>>>>>
>>>>>>>>>>>>>
>>>>>>>>>>>>> On Fri, Oct 28, 2016 at 6:41 PM, Victor Denisov <vdenisov@xxxxxxxxxxxx> wrote:
>>>>>>>>>>>>>> Another thing that bothers me. When we remove an image from a consistency group.
>>>>>>>>>>>>>> Should we remove all snapshots of this image that were created as part
>>>>>>>>>>>>>> of a consistency group snapshot?
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> The easiest solution would be to remove all snapshots that are in
>>>>>>>>>>>>>> GroupSnapshotNamespace and reference this consistency group.
>>>>>>>>>>>>>> I looked into cinder docs for this feature:
>>>>>>>>>>>>>> http://docs.openstack.org/admin-guide/blockstorage-consistency-groups.html
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> But it's not clear to me which behavior cinder expects.
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> Thanks,
>>>>>>>>>>>>>> V.
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> On Wed, Oct 26, 2016 at 6:16 AM, Jason Dillaman <jdillama@xxxxxxxxxx> wrote:
>>>>>>>>>>>>>>> In a perfect world, it would be nice to add a new optional to "rbd
>>>>>>>>>>>>>>> snap ls" to show all snapshots (with a new column to indicate the
>>>>>>>>>>>>>>> associated namespace).
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> On Tue, Oct 25, 2016 at 11:07 PM, Victor Denisov <vdenisov@xxxxxxxxxxxx> wrote:
>>>>>>>>>>>>>>>> Question. When we print out snapshots of an image, should the group
>>>>>>>>>>>>>>>> snapshots be listed, or should they be marked as special snapshots?
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> Thanks,
>>>>>>>>>>>>>>>> V.
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> On Mon, Oct 10, 2016 at 3:14 PM, Victor Denisov <vdenisov@xxxxxxxxxxxx> wrote:
>>>>>>>>>>>>>>>>> Ok. I didn't have any intention to throw exceptions.
>>>>>>>>>>>>>>>>> I was more concerned about whether it's ok to allocate and delete
>>>>>>>>>>>>>>>>> objects or I should use smart pointers.
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> On Mon, Oct 10, 2016 at 7:18 AM, Jason Dillaman <jdillama@xxxxxxxxxx> wrote:
>>>>>>>>>>>>>>>>>> The only place exceptions are routinely used is within the "::decode"
>>>>>>>>>>>>>>>>>> functions. I would prefer to see the code not throwing new exceptions
>>>>>>>>>>>>>>>>>> on purpose.
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> On Fri, Oct 7, 2016 at 2:26 PM, Victor Denisov <vdenisov@xxxxxxxxxxxx> wrote:
>>>>>>>>>>>>>>>>>>> Are any exceptions used in librbd code? Should the code be exception safe?
>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>> Thanks,
>>>>>>>>>>>>>>>>>>> V.
>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>> On Fri, Sep 16, 2016 at 10:37 AM, Jason Dillaman <jdillama@xxxxxxxxxx> wrote:
>>>>>>>>>>>>>>>>>>>> On Thu, Sep 15, 2016 at 7:17 PM, Victor Denisov <vdenisov@xxxxxxxxxxxx> wrote:
>>>>>>>>>>>>>>>>>>>>> if (struct_v >= 5) {
>>>>>>>>>>>>>>>>>>>>> ::decode(snapshot_namespace, p);
>>>>>>>>>>>>>>>>>>>>> } else {
>>>>>>>>>>>>>>>>>>>>> snapshot_namespace = cls::rbd::UserSnapshotNamespace();
>>>>>>>>>>>>>>>>>>>>> }
>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>> then code for ::encode function of cls_rbd_snap would change accordingly:
>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>> instead of
>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>> boost::apply_visitor(cls::rbd::EncodeSnapshotTypeVisitor(bl),
>>>>>>>>>>>>>>>>>>>>> snapshot_namespace);
>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>> I would do:
>>>>>>>>>>>>>>>>>>>>> ::encode(snapshot_namespace, bl);
>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>> +1 -- looks good to me
>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>> --
>>>>>>>>>>>>>>>>>>>> Jason
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> --
>>>>>>>>>>>>>>>>>> Jason
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> --
>>>>>>>>>>>>>>> Jason
>>>>>>>>>>>>>
>>>>>>>>>>>>>
>>>>>>>>>>>>>
>>>>>>>>>>>>> --
>>>>>>>>>>>>> Jason
>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>>> --
>>>>>>>>>>>> Jason
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> --
>>>>>>>>>> Jason
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>> --
>>>>>>>> Jason
>>>>>>
>>>>>>
>>>>>>
>>>>>> --
>>>>>> Jason
>>>>
>>>>
>>>>
>>>> --
>>>> Jason
>
>
>
> --
> Jason
--
To unsubscribe from this list: send the line "unsubscribe ceph-devel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
