openstack team mailing list archive

[Gabe Westmaas <gabe.westmaas@xxxxxxxxxxxxx>]

This actually sounds like it covers most of the first run needs in this
etherpad:

http://etherpad.openstack.org/FolsomGlanceImageReplication


Definitely excited to see the tool, and then I wonder if we can just add a
few things to it to get metadata and filtering support.  Sounds like ec2
stuff is being covered.

Would it make sense to use image metadata to communicate where (and
therefore if) an image should be replicated to?  I'm imagining a list of
endpoints that the tool could read and then copy the image to (unless the
tool was running in copy all to endpoint X mode as I imagine it does now).
 Auth is going to be an issue here if a glance endpoint is specified that
doesn't share the operator's auth.  This isn't terribly transparent to the
customer either since there isn't really a way to set any sort of fault
for a customer to see.

I guess one other thing to note is that we definitely have different use
cases: many operators probably want full control of what gets replicated,
whereas we are happy to let customers choose which specific images to
replicate and then charge for that service.  Hopefully we can come to
something that supports both.

This isn't required for the first run, but we could add a property that
indicates the "replicated at" time on the destination so that we can just
compare the updated at of the master image with the replicated at on the
slave, and if they match, there's no need to re-replicate.  Possibly
that's just as expensive as replicating all the metadata though.

Gabe

On 5/2/12 10:24 PM, "Michael Still" <michael.still@xxxxxxxxxxxxx> wrote:

>Hi.
>
>I'd be interested in hearing from people who have implemented some form
>of replication with glance. I'm especially interested in how you went
>about it. I attended the session at the dev summit, but that was forward
>looking, and I am pretty sure that there wasn't any mention of current
>implementations.
>
>I'll get the ball rolling -- I have just implemented API level
>replication for glance for an internal project. It uses the glance API
>to replicate images from a master glance to slave glances. Its not very
>smart at the moment, it just copies everything.
>
>Current warts:
> - no support for metadata update
> - no support for filtering of what is replicated
> - maintaining amazon ec2 ids across regions requires twiddling the nova
>database where this mapping is stored
>
>Advantages of this approach:
> - API level replication means that I can run different versions of
>glance at each end of the replication relationship
> - it really wasn't that hard to do
>
>Would other people be interested in getting this code into glance,
>probably as a stand alone command line tool? Or has someone done
>something much better that I should be using instead?
>
>Cheers,
>Mikal
>
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