Open Stack

On Mon, Oct 20, 2014 at 7:04 AM, Jamie Lennox <jamielennox at redhat.com>
wrote:

>
>
> ----- Original Message -----
> > From: "Dolph Mathews" <dolph.mathews at gmail.com>
> > To: "OpenStack Development Mailing List (not for usage questions)" <
> openstack-dev at lists.openstack.org>
> > Sent: Tuesday, October 7, 2014 6:56:15 PM
> > Subject: Re: [openstack-dev] Horizon and Keystone: API Versions and
> Discovery
> >
> >
> >
> > On Tuesday, October 7, 2014, Adam Young < ayoung at redhat.com > wrote:
> >
> >
> > Horizon has a config options which says which version of the Keystone
> API it
> > should work against: V2 or V3. I am not certain that there is still any
> > reason for Horizon to go against V2. However, If we defer the decision to
> > Keystone, we come up against the problem of discovery.
> >
> > On the surface it is easy, as the Keystone client supports version
> discovery.
> > The problem is that discovery must be run for each new client creation,
> and
> > Horizon uses a new client per request. That would mean that every
> request to
> > Horizon that talks to Keystone would generate at least one additional
> > request.
> >
> >
> >
> > The response is cacheable.
>
> Not only is it cachable it is cached by default within the Session object
> you use so that the session will only make one discovery request per
> service per session. So horizon can manage how long to cache discovery for
> by how long they hold on to a session object. As the session object doesn't
> contain any personal or sensitive date (that is all restricted to the auth
> plugin) the session object can be persisted between requests.
>

Is there any reason not to cache to disk across sessions? The GET response
is entirely endpoint-specific, not exactly session-based.


>
> Whether or not horizon works that way today - and whether the other
> services work with discovery as well as keystone does i'm not sure.
>
> >
> > Is this significant?
> >
> > It gets a little worse when you start thinking about all of the other
> > services out there. If each new request that has to talk to multiple
> > services needs to run discovery, you can image that soon the majority of
> > network chatter would be discovery based.
> >
> >
> > It seems to me that Horizon should somehow cache this data, and share it
> > among clients. Note that I am not talking about user specific data like
> the
> > endpoints from the service catalog for a specific project. But the
> overall
> > service catalog, as well as the supported versions of the API, should be
> > cacheable. We can use the standard HTTP cache management API on the
> Keystone
> > side to specify how long Horizon can trust the data to be current.
> >
> > I think this actually goes for the rest of the endpoints as well: we
> want to
> > get to a much smaller service catalog, and we can do that by making the
> > catalog holds on IDs. The constraints spec for endpoint binding will be
> > endpoint only anyway, and so having the rest of the endpoint data cached
> > will be valuable there as well.
> >
> >
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> >
>
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