On 11/04/2013 03:49 PM, Solly Ross wrote:
So, There's currently an outstanding issue with regards to a Nova
shortcut command that creates a volume from an image and then boots
from it in one fell swoop. The gist of the issue is that there is
currently a set timeout which can time out before the volume creation
has finished (it's designed to time out in case there is an error),
in cases where the image download or volume creation takes an
extended period of time (e.g. under a Gluster backend for Cinder with
certain network conditions).
The proposed solution is a modification to the Cinder API to provide
more detail on what exactly is going on, so that we could
programmatically tune the timeout. My initial thought is to create a
new column in the Volume table called 'status_detail' to provide more
detailed information about the current status. For instance, for the
'downloading' status, we could have 'status_detail' be the completion
percentage or JSON containing the total size and the current amount
copied. This way, at each interval we could check to see if the
amount copied had changed, and trigger the timeout if it had not,
instead of blindly assuming that the operation will complete within a
given amount of time.
What do people think? Would there be a better way to do this?
The only other option I can think of would be some kind of callback that
cinder could explicitly call to drive updates and/or notifications of
faults rather than needing to wait for a timeout. Possibly a
combination of both would be best, that way you could add a --poll
option to the "create volume and boot" CLI command.
I come from the kernel-hacking world and most things there involve
event-driven callbacks. Looking at the openstack code I was kind of
surprised to see hardcoded timeouts and RPC casts with no callbacks to
indicate completion.
Chris
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