[openstack-dev] [Glance][Keystone] Glance and trusts

Adam Young ayoung at redhat.com
Wed Jun 3 20:03:57 UTC 2015

On 06/02/2015 12:57 PM, Mikhail Fedosin wrote:
> Hello! I think it's a good time to discuss implementation of trusts in 
> Glance v2 and v3 api.
> Currently we have two different situations during image creation where 
> our token may expire, which leads to unsuccessful operation.
> First is connection between glance-api and glance-registry. In this 
> case we have a solution (https://review.openstack.org/#/c/29967/) - 
> use_user_token parameter in glance-api.conf, but it is True by default 
> . If it's changed to False then glance-api will use its own 
> credentials to authorize in glance-registry and it prevents many 
> possible issues with user token expiration. So, I'm interested if 
> there are some performance degradations if we change use_user_token to 
> False and what are the reasons against making it the default value.
> Second one is linked with Swift. Current implementation uploads chunks 
> one by one and requires authorization each time. It may lead to 
> problems: for example we have to upload 100 chunks, after 99th one, 
> token expired and glance can't upload the last one, catches an 
> exception and tries to remove stale chunks from storage. Of course it 
> will fail, because token is not valid anymore, and that's why there 
> will be 99 garbage objects in the storage.
> With Single-tenant mode glance uses its own credentials to upload 
> files, so it's possible to create new connection on each chunk upload 
> or catch Unauthorized exception and recreate connections only in that 
> cases. But with Multi-tenant mode there is no way to do it, because 
> user credentials are required. So it seems that trusts is the only one 
> solution here.
The problem with using trusts is that it would need to be created 
per-user, and that is going to be expensive.  It would be possible, as 
Heat does something of this nature:

1. User calls glance,
2. Glance creates a trust with some limitation, either time or number of 
3.  Trusts are used for all operations with swift.
4. Glance should clean up the trust when it is complete.

I don't love the solution, but I think it is the best we have. Ideally 
the user would opt in to the trust, but in this case, it is kindof 
implicit by them calling the API.

We should limit the trust creation to only have those roles (or a 
subset) on the token used to create the trust.

> I would be happy to hear your opinions on that matter. If you know 
> other situations where trusts are useful or some other approaches 
> please share.
> Best regards,
> Mike Fedosin
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