On Tue, Jul 7, 2020 at 5:05 PM Łukasz Kołaciński <l.kolacinski@storware.eu> wrote:

Dear ovirt community,

Hi Łukasz,

Adding devel@ovit.org since this topic is more appropriate for the devel list.

I am trying to use ovirt imageio api to receive changed blocks (dirty bitmap) on ovirt 4.4. Could anyone tell me how to get them step by step? On the documentation I saw endpoint "GET /images/ticket-uuid/map". I don't know what ticket-uuid is and how to generate it. I also need to know how to use this api because I can't reach it via /ovirt-engine/api/

I am asking about this endpoint:

https://www.ovirt.org/documentation/incremental-backup-guide/incremental-backup-guide.html#imageio-backup-api

This guide is outdated and should not be used now.

The most up to date information is here:

https://www.ovirt.org/develop/release-management/features/storage/incremental-backup.html

However the extents API is also outdated in the feature page. We are working on updating it.

So here is example:

First you must start backup with from_checkpoint_id argument:

backup = backups_service.add(
types.Backup(
disks=disks,
from_checkpoint_id="checkpoint-id",
)
)

"checkpoint-id" is the checkpoint created in the last backup.

This starts a backup in in incremental mode. Dirty extents are available only

in this mode.

Then you start a transfer for download, using the backup id:

transfer = imagetransfer.create_transfer(
connection,
disk,
types.ImageTransferDirection.DOWNLOAD,
backup=types.Backup(id=backup_uuid))

The transfer.transfer_url is the URL to download from, for example:

https://host:54322/images/53787351-3f72-44a1-8a26-1323524fac4a

Connect to host:54322 and send this request:

GET /images/53787351-3f72-44a1-8a26-1323524fac4a/extents?context=dirty

And parse the return json list, containing objects like:

[

{"start": 0, "length": 65536, "dirty": true},

{"start": 65536, "length": 1048576, "dirty": false},

...

]

For example code of using the imageio API, see imageio http backend:

https://github.com/oVirt/ovirt-imageio/blob/d5aa0e1fe659f1bf1247516f83c71e072803fa05/daemon/ovirt_imageio/_internal/backends/http.py#L288

https://github.com/oVirt/ovirt-imageio/blob/d5aa0e1fe659f1bf1247516f83c71e072803fa05/daemon/ovirt_imageio/_internal/backends/http.py#L498

We are adding a ImageioClient API that makes it easier to consume without

writing any HTTP code:

https://gerrit.ovirt.org/c/110068

With this you can use:

with ImageioClient(transfer.transfer_url, cafile=args.cafile) as client:

for extent in client.extent("dirty"):

if extent.dirty:

print("##dirty start={} length={}".format(extent.start, extent.length))

client.write_to(sys.stdout.buffer, extent.start, extent.length)

print()

This will stream the dirty extents to stdout. Not very useful as is, but illustrates how

you can consume the data.

Here is an example writing extents to a sparse stream format:

https://gerrit.ovirt.org/c/110069

For complete backup example code see:

https://github.com/oVirt/ovirt-engine-sdk/blob/master/sdk/examples/backup_vm.py

Note the new imagetransfer helper module:

https://github.com/oVirt/ovirt-engine-sdk/blob/master/sdk/examples/helpers/imagetransfer.py

Nir

e-mail: l.kolacinski@storware.eu

ul. Leszno 8/44
01-192 Warszawa
www.storware.eu

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