[openstack-dev] [nova] ability to set metadata on instances (but config drive is not updated)

Chris Friesen chris.friesen at windriver.com
Tue Jun 21 21:48:46 UTC 2016

On 06/19/2016 11:57 AM, Clint Byrum wrote:
> Excerpts from Joshua Harlow's message of 2016-06-17 15:04:38 -0700:

>> Now if I am using the configdrive instead of the metadata server at that
>> special/magic ip that same metadata never seems to change (I assume the
>> configdrive would have to be 'ejected' and then a new configdrive
>> created and then that configdrive 'reinserted'); was anyone aware of a
>> bug that would solve this (it does appear to be a feature difference
>> that could/should? be solved)?

> That's not a bug. AFAIK, it was never intended to be updated.


>> Why this is something useful (from my view) is that we (at godaddy) have
>> a cron job that polls that metadata periodically and it generates a
>> bunch of polling traffic (especially when each VM does this) and that
>> traffic could be removed if such a 'eject' and 'reinsert' happens
>> instead (since then the cron job could become a small program that
>> listens for devices being inserted/removed and does the needed actions
>> then, which is better than polling endlessly for data that hasn't changed).
> I think you're abusing Nova to do what your config management system
> should be doing. The config drive and metadata service are not meant
> to be continuously polled or updated, they're for bootstrapping into
> a continuous config management system.

While this is true, it seems to be a commonly-requested item.  I just had a 
customer rep asking whether we support updating instance metadata for a running 
instance, since apparently it's possible with AWS.


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