[openstack-dev] [Neutron][LBaaS] Unanswered questions in object model refactor blueprint

Brandon Logan brandon.logan at RACKSPACE.COM
Wed May 28 19:01:23 UTC 2014


Hi Vijay,

On Tue, 2014-05-27 at 16:27 -0700, Vijay B wrote:
> Hi Brandon,
> 
> 
> The current reviews of the schema itself are absolutely valid and
> necessary, and must go on. However, the place of implementation of
> this schema needs to be clarified. Rather than make any changes
> whatsoever to the existing neutron db schema for LBaaS, this new db
> schema outlined needs to be implemented for a separate LBaaS core
> service.
> 
Are you suggesting a separate lbaas database from the neutron database?
If not, then I could use some clarification. If so, I'd advocate against
that right now because there's just too many things that would need to
be changed.  Later, when LBaaS becomes its own service then yeah that
will need to happen.
> 
> What we should be providing in neutron is a switch (a global conf)
> that can be set to instruct neutron to do one of two things:
> 
> 
> 1. Use the existing neutron LBaaS API, with the backend being the
> existing neutron LBaaS db schema. This is the status quo.
> 2. Use the existing neutron LBaaS API, with the backend being the new
> LBaaS service. This will invoke calls not to neutron's current LBaaS
> code at all, rather, it will call into a new set of proxy "backend"
> code in neutron that will translate the older LBaaS API calls into the
> newer REST calls serviced by the new LBaaS service, which will write
> down these details accordingly in its new db schema. As long as the
> request and response objects to legacy neutron LBaaS calls are
> preserved as is, there should be no issues. Writing unit tests should
> also be comparatively more straightforward, and old functional tests
> can be retained, and newer ones will not clash with legacy code.
> Legacy code itself will work, having not been touched at all. The
> blueprint for the db schema that you have referenced
> (https://review.openstack.org/#/c/89903/5/specs/juno/lbaas-api-and-objmodel-improvement.rst) should be implemented for this new LBaaS service, post reviews.
> 
I think the point of this blueprint is to get the API and object model
less confusing for the Neutron LBaaS service plugin.  I think it's too
early to create an LBaaS service because we have not yet cleaned up the
tight integration points between Neutron LBaaS and LBaaS.  Creating a
new service would require only API interactions between Neutron and this
LBaaS service, which currently is not possible due to these tight
integration points.  

> 
> The third option would be to turn off neutron LBaaS API, and use the
> new LBaaS core service directly, but for this we can simply disable
> neutron lbaas, and don't need a config parameter in neutron.
> 
> 
> Implementing this db schema within neutron instead will be not just
> complicated, but a huge effort that will go waste in future once the
> new LBaaS service is implemented. Also, migration will unnecessarily
> retain the same steps needed to go from legacy neutron LBaaS to the
> new core LBaaS service in this approach (twice, in succession) in case
> for any reason the version goes from legacy neutron LBaaS -> new
> neutron LBaaS -> new LBaaS core service.
I totally agree that this is technical debt, but I believe it is the
best option we have right now since LBaaS needs to live in the Neutron
code and process because of the tight integration points.  Since this
object model refactor has been slated for Juno, and these tight
integration points may or may not be cleaned up by Juno, staying within
Neutron seems to be the best option right now.
> 
> 
> Going forward, the legacy neutron LBaaS API can be deprecated, and the
> new API that directly contacts the new LBaaS core service can be used.
> 
> 
> We have discussed the above architecture previously, but outside of
> the ML, and a draft of the blueprint for this new LBaaS core service
> is underway, and is a collation of all the discussions among a large
> number of LBaaS engineers including yourself during the summit - I
> will be posting it for review within a couple of days, as planned.
> 
> 
> 
> 
> Regards,
> Vijay
> 
> 
> On Tue, May 27, 2014 at 12:32 PM, Brandon Logan
> <brandon.logan at rackspace.com> wrote:
>         Referencing this blueprint:
>         https://review.openstack.org/#/c/89903/5/specs/juno/lbaas-api-and-objmodel-improvement.rst
>         
>         Anyone who has suggestions to possible issues or can answer
>         some of
>         these questions please respond.
>         
>         
>         1. LoadBalancer to Listener relationship M:N vs 1:N
>         The main reason we went with the M:N was so IPv6 could use the
>         same
>         listener as IPv4.  However this can be accomplished by the
>         user just
>         creating a second listener and pool with the same
>         configuration.  This
>         will end up being a bad user experience when the listener and
>         pool
>         configuration starts getting complex (adding in TLS, health
>         monitors,
>         SNI, etc). A good reason to not do the M:N is because the
>         logic on might
>         get complex when dealing with status.  I'd like to get
>         people's opinions
>         on this on whether we should do M:N or just 1:N.  Another
>         option, is to
>         just implement 1:N right now and later implement the M:N in
>         another
>         blueprint if it is decided that the user experience suffers
>         greatly.
>         
>         My opinion: I like the idea of leaving it to another blueprint
>         to
>         implement.  However, we would need to watch out for any major
>         architecture changes in the time itis not implemented that
>         could make
>         this more difficult than what it needs to be.
>         
>         2. Pool to Health Monitor relationship 1:N vs 1:1
>         Currently, I believe this is 1:N however it was suggested to
>         deprecate
>         this in favor of 1:1 by Susanne and Kyle agreed.  Are there
>         any
>         objections to channging to 1:1?
>         
>         My opinion: I'm for 1:1 as long as there aren't any major
>         reasons why
>         there needs to be 1:N.
>         
>         3. Does the Pool object need a status field now that it is a
>         pure
>         logical object?
>         
>         My opinion: I don't think it needs the status field.  I think
>         the
>         LoadBalancer object may be the only thing that needs a status,
>         other
>         than the pool members for health monitoring.  I might be
>         corrected on
>         this though.
>         
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