Open Stack

On Tue, 2018-12-04 at 12:08 +0100, Flavio Percoco wrote:
> Greetings,
> 
> I've been working on a tool that requires creating CoreOS nodes on
> OpenStack. Sadly, I've hit the user data limit, which has blocked the
> work I'm doing.
> 
> One big difference between CoreOS images and other cloud images out
> there is that CoreOS images don't use cloud-init but a different tool
> called Ignition[0], which uses JSON as its serialization format.
> 
> The size of the configs that I need to pass to the instance is bigger
> than the limit imposed by Nova. I've worked on reducing the size as
> much as possible and even generating a compressed version of it but
> the data is still bigger than the limit (144 kb vs 65kb).
> 
> I'd like to understand better what the nature of the limit is (is it
> because of the field size in the database? Is it purely an API limit?
> Is it because it causes problems depending on the vendor? As far as I
> can tell the limit is just being enforced by the API schema[1] and
> not
> the DB as it uses a MEDIUMTEXT field.
> 
> I realize this has been asked before but I wanted to get a feeling of
> the current opinion about this. Would the Nova team consider
> increasing the limit of the API considering that more use cases like
> this may be more common these days?

I think EC2 only gives you 1/4 of what Nova does (16KB or so). So it
would seem Nova is already being somewhat generous here.

I don't see any harm in increasing it so long as the DB supports it (no
DB schema change would be required).

I wonder if pairing userdata with a token that allowed you to download
the information from another (much larger) data source would be a
better pattern here though. Then you could make it as large as you
needed.

Dan

> 
> [0] https://coreos.com/ignition/docs/latest/
> [1] 
> https://github.com/openstack/nova/blob/master/nova/api/openstack/compute/schemas/servers.py#L212-L215
> 
> Thanks,
> Flavio
>