[openstack-dev] [Neutron] UniqueConstraint for name and tenant_id in security group

Mathieu Gagné mgagne at iweb.com
Thu Dec 11 23:05:01 UTC 2014

On 2014-12-11 8:43 AM, Jay Pipes wrote:
> I'm generally in favor of making name attributes opaque, utf-8 strings
> that are entirely user-defined and have no constraints on them. I
> consider the name to be just a tag that the user places on some
> resource. It is the resource's ID that is unique.
> I do realize that Nova takes a different approach to *some* resources,
> including the security group name.
> End of the day, it's probably just a personal preference whether names
> should be unique to a tenant/user or not.

We recently had an issue in production where a user had 2 "default" 
security groups (for reasons we have yet to identify). For the sack of 
completeness, we are running Nova+Neutron Icehouse.

When no security group is provided, Nova will default to the "default" 
security group. However due to the fact 2 security groups had the same 
name, nova-compute got confused, put the instance in ERROR state and 
logged this traceback [1]:

   NoUniqueMatch: Multiple security groups found matching 'default'. Use 
an ID to be more specific.

I do understand that people might wish to create security groups with 
the same name.

However I think the following things are very wrong:

- the instance request should be blocked before it ends up on a compute 
node with nova-compute. It shouldn't be the job of nova-compute to find 
out issues about duplicated names. It should be the job of nova-api. 
Don't waste your time scheduling and spawning an instance that will 
never spawn with success.

- From an end user perspective, this means "nova boot" returns no error 
and it's only later that the user is informed of the confusion with 
security group names.

- Why does it have to crash with a traceback? IMO, traceback means "we 
didn't think about this use case, here is more information on how to 
find the source". As an operator, I don't care about the traceback if 
it's a known limitation of Nova/Neutron. Don't pollute my logs with 
"normal exceptions". (Log rationalization anyone?)

Whatever comes out of this discussion about security group name 
uniqueness, I would like those points to be addressed as I feel those 
aren't great users/operators experience.

[1] http://paste.openstack.org/show/149618/


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