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Ultimately, as we will have several objects which have many-to-many
relationships with other objects, the 'status' of an object that is shared
between what will ultimately be two separate physical entities on the
back-end should be represented by a dictionary, and any 'reduction' of this
on behalf of the user should happen within the UI. It does make things more
complex to deal with in certain kinds of failure scenarios, but we don't
help ourselves at all by trying to hide, say, when a member of a pool
referenced by one listener is 'UP' and the same member of the same pool
referenced by a different listener is 'DOWN'.  :/

Granted, our version 1 implementation of these objects is going to be
simplified, but it doesn't hurt to think about where we're headed with this
API and object model.

I think it would be worthwhile for someone to produce a status matrix
showing which kinds of status are available for each object type, and what
the possible values of those statuses are, and what they mean. Given the
question of what 'status' means is very complicated indeed, I think this is
the only way we're going to actually make forward progress in this
discussion.

Stephen



On Tue, Jun 24, 2014 at 4:02 PM, Dustin Lundquist <dustin at null-ptr.net>
wrote:

> I think there is significant value in having status on the listener object
> even in the case of HAProxy. While HAProxy can support multiple listeners
> in a single process, there is no reason it needs to be deployed that way.
> Additionally in the case of updating a configuration with an additional
> listener, the other listeners and the load balancer object are not in an
> unavailable or down state before the configuration is applied, only the new
> listener object is down or building. In the case of the HAProxy namespace
> driver, one could map the namespace creation and HAProxy process to the
> load balancer object status, but each listener can have its own status
> based on the availability of members in its pools.
>
> For the initial version of our new object model we be pragmatic and
> minimize complexity and change, we can preform a reduction across all
> listeners to generate an overall load balancer status.
>
>
> -Dustin
>
>
> On Tue, Jun 24, 2014 at 3:15 PM, Vijay B <os.vbvs at gmail.com> wrote:
>
>> Hi Brandon, Eugene, Doug,
>>
>> During the hackathon, I remember that we had briefly discussed how
>> listeners would manifest themselves on the LB VM/device, and it turned out
>> that for some backends like HAProxy it simply meant creating a frontend
>> entry in the cfg file whereas on other solutions it could mean spawning a
>> process/equivalent. So we must have status fields to track the state of any
>> such entities that are actually created. In the listener case, an ACTIVE
>> state would mean that the appropriate backend processes have been created
>> or that the required config file entries have been made.
>>
>> I like the idea of having relational objects and setting the status on
>> them, and in our case we can use the status fields
>> (pool/healthmonitor/listener) in each table to denote the state of the
>> relationship (configuration/association on backend) to another object like
>> LoadBalancer. So I think the status fields should stay.
>>
>> In this scenario, some entities' status could be updated in lbaas proper,
>> and some in the driver implementation. I don't have a strict preference as
>> to which among lbaas proper or the driver layer announces the status since
>> we discussed on the IRC that we'd have helper functions in the driver to do
>> these updates.
>>
>>
>> Regards,
>> Vijay
>>
>>
>> On Tue, Jun 24, 2014 at 12:16 PM, Brandon Logan <
>> brandon.logan at rackspace.com> wrote:
>>
>>> On Tue, 2014-06-24 at 18:53 +0000, Doug Wiegley wrote:
>>> > Hi Brandon,
>>> >
>>> > I think just one status is overloading too much onto the LB object
>>> (which
>>> > is perhaps something that a UI should do for a user, but not something
>>> an
>>> > API should be doing.)
>>>
>>> That is a good point and perhaps its another discussion to just have
>>> some way to show the status an entity has for each load balancer, which
>>> is what mark suggested for the member status at the meet-up.
>>>
>>> >
>>> > > 1) If an entity exists without a link to a load balancer it is purely
>>> > > just a database entry, so it would always be ACTIVE, but not really
>>> > > active in a technical sense.
>>> >
>>> > Depends on the driver.  I don¹t think this is a decision for lbaas
>>> proper.
>>>
>>> Driver is linked to the flavor or provider.  Flavor or provider will/is
>>> linked to load balancer.  We won't be able get a driver to send anything
>>> to if there isn't a load balancer.  Without a driver it is a decision
>>> for lbaas proper.  I'd be fine with setting the status of these
>>> "orphaned" entities to just ACTIVE but I'm just worried about the status
>>> management in the future.
>>>
>>> >
>>> >
>>> > > 2) If some of these entities become shareable then how does the
>>> status
>>> > > reflect that the entity failed to create on one load balancer but was
>>> > > successfully created on another.  That logic could get overly
>>> complex.
>>> >
>>> > That¹s a status on the join link, not the object, and I could argue
>>> > multiple ways in which that should be one way or another based on the
>>> > backend, which to me, again implies driver question (backend could
>>> queue
>>> > for later, or error immediately, or let things run degraded, orŠ)
>>>
>>> Yeah that is definitely an argument.  I'm just trying to keep in mind
>>> the complexities that could arise from decisions made now.  Perhaps it
>>> is the wrong way to look at it to some, but I don't think thinking about
>>> the future is a bad thing and should never be done.
>>>
>>> >
>>> > Thanks,
>>> > Doug
>>> >
>>> >
>>> >
>>> >
>>> > On 6/24/14, 11:23 AM, "Brandon Logan" <brandon.logan at RACKSPACE.COM>
>>> wrote:
>>> >
>>> > >I think we missed this discussion at the meet-up but I'd like to bring
>>> > >it up here.  To me having a status on all entities doesn't make much
>>> > >sense, and justing having a status on a load balancer (which would be
>>> a
>>> > >provisioning status) and a status on a member (which would be an
>>> > >operational status) are what makes sense because:
>>> > >
>>> > >1) If an entity exists without a link to a load balancer it is purely
>>> > >just a database entry, so it would always be ACTIVE, but not really
>>> > >active in a technical sense.
>>> > >
>>> > >2) If some of these entities become shareable then how does the status
>>> > >reflect that the entity failed to create on one load balancer but was
>>> > >successfully created on another.  That logic could get overly complex.
>>> > >
>>> > >I think the best thing to do is to have the load balancer status
>>> reflect
>>> > >the provisioning status of all of its children.  So if a health
>>> monitor
>>> > >is updated then the load balancer that health monitor is linked to
>>> would
>>> > >have its status changed to PENDING_UPDATE.  Conversely, if a load
>>> > >balancer or any entities linked to it are changed and the load
>>> > >balancer's status is in a non-ACTIVE state then that update should not
>>> > >be allowed.
>>> > >
>>> > >Thoughts?
>>> > >
>>> > >Thanks,
>>> > >Brandon
>>> > >
>>> > >
>>> > >_______________________________________________
>>> > >OpenStack-dev mailing list
>>> > >OpenStack-dev at lists.openstack.org
>>> > >http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev
>>> >
>>> >
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-- 
Stephen Balukoff
Blue Box Group, LLC
(800)613-4305 x807
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