Open Stack

Hi Vincent, Zhi, Huiba, sorry for delayed response. See comments inline.

On Tue, 2014-04-22 at 10:59 +0800, Sheng Bo Hou wrote:
> I actually support the idea Huiba has proposed, and I am thinking of
> how to optimize the large data transfer(for example, 100G in a short
> time) as well. 
> I registered two blueprints in nova-specs, one is for an image upload
> plug-in to upload the image to
> glance(https://review.openstack.org/#/c/84671/), the other is a data
> transfer plug-in(https://review.openstack.org/#/c/87207/) for data
> migration among nova nodes. I would like to see other transfer
> protocols, like FTP, bitTorrent, p2p, etc, implemented for data
> transfer in OpenStack besides HTTP. 
> 
> Data transfer may have many use cases. I summarize them into two
> catalogs. Please feel free to comment on it. 
> 1. The machines are located in one network, e.g. one domain, one
> cluster, etc. The characteristic is the machines can access each other
> directly via the IP addresses(VPN is beyond consideration). In this
> case, data can be transferred via iSCSI, NFS, and definitive zero-copy
> as Zhiyan mentioned. 
> 2. The machines are located in different networks, e.g. two data
> centers, two firewalls, etc. The characteristic is the machines can
> not access each other directly via the IP addresses(VPN is beyond
> consideration). The machines are isolated, so they can not be
> connected with iSCSI, NFS, etc. In this case, data have to go via the
> protocols, like HTTP, FTP, p2p, etc. I am not sure whether zero-copy
> can work for this case. Zhiyan, please help me with this doubt. 
> 
> I guess for data transfer, including image downloading, image
> uploading, live migration, etc, OpenStack needs to taken into account
> the above two catalogs for data transfer.

For live migration, we use shared storage so I don't think it's quite
the same as getting/putting image bits from/to arbitrary locations.

>  It is hard to say that one protocol is better than another, and one
> approach prevails another(BitTorrent is very cool, but if there is
> only one source and only one target, it would not be that faster than
> a direct FTP). The key is the use
> case(FYI:http://amigotechnotes.wordpress.com/2013/12/23/file-transmission-with-different-sharing-solution-on-nas/).

Right, a good solution would allow for some flexibility via multiple
transfer drivers.

> Jay Pipes has suggested we figure out a blueprint for a separate
> library dedicated to the data(byte) transfer, which may be put in oslo
> and used by any projects in need (Hoping Jay can come in:-)). Huiba,
> Zhiyan, everyone else, do you think we come up with a blueprint about
> the data transfer in oslo can work?

Yes, so I believe the most appropriate solution is to create a library
-- in oslo or a standalone library like taskflow -- that would offer a
simple byte streaming library that could be used by nova.image to expose
a neat and clean task-based API.

Right now, there is a bunch of random image transfer code spread
throughout nova.image and in each of the virt drivers there seems to be
different re-implementations of similar functionality. I propose we
clean all that up and have nova.image expose an API so that a virt
driver could do something like this:

from nova.image import api as image_api

...

task = image_api.copy(from_path_or_uri, to_path_or_uri)
# do some other work
copy_task_result = task.wait()

Within nova.image.api.copy(), we would use the aforementioned transfer
library to move the image bits from the source to the destination using
the most appropriate method.

Best,
-jay