On Tue, Apr 10, 2018 at 6:53 PM Richard W.M. Jones <
address@hidden> wrote:
...
Dan Berrange pointed out earlier on that it might be easier if imageio
just exposed NBD, or if we found a way to tunnel NBD requests over web
sockets (in the format case nbdkit would not be needed, in the latter
case nbdkit could act as a bridge).
I think we can expose NBD using ndb-server and dynamic exports.
It can work like this:
0. Install nbd and enable nbd-server on a host, running
as vdsm:kvm, not exporting anything.
1. User starts transfer session via oVirt API with protocol="nbd"
(if not specified, use "https" for backward compatibility)
2. oVirt selects a host for the transfer and configures an export
in that host - for example:
[bbff5ab7-2e8e-45b8-a497-423c2d2b3ff1]
exportname = /path/to/image
trim = yes
timeout = 300
nbd-server supports reloading configuration via SIGHUP.
Looks like it should work for adding export dynamically:
I could find code handling removing exports.
3. User gets back
- transfer_url: "nbd:hostname:port"
- export_name: bbff5ab7-2e8e-45b8-a497-423c2d2b3ff1
Assuming that if NBD_OPT_EXPORT_NAME is bbff5ab7-2e8e-45b8-a497-423c2d2b3ff1
ndb-server will export the /path/to/image mentioned in the config exportname.
This seems to be the case based on:
4. User transmit data using nbd-client or qemu-img or maybe
a wrapper script to make it easier
5. During the transfer, oVirt monitors progress and activity.
I don't see how we can do this with current nbd-server.
6. User ends the transfer session via oVirt API
7. oVirt removes the export and finalize the transfer.
I guess this can work in a similar way for KubeVirt. The way
the image is provisioned and attached to a host will be
different, but the way a user will transfer image data can be
the same.
Seems that nbd-server is missing:
- way to remove exports dynamically
- way to monitor export activity and progress
Nir