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On Tue, 2016-11-01 at 13:13 +0100, Ihar Hrachyshka wrote:
> Brandon Logan <brandon.logan at rackspace.com> wrote:
> 
> > Hello Neutrinos,
> > I've come across an issue that I'd like to get input/opinions
> > on.  I've
> > been reviewing some of the centralize config options reviews and
> > have
> > come across a few that would cause issues with other projects that
> > are
> > importing these options, especially stadium projects.  High level
> > view
> > of the issue:
> > 
> > [1] would cause at least 22 projects to need to be fixed based on
> > [2]
> > [3] would cause at least 12 projects to need to be fixed based on
> > [4]
> > 
> > [5] looks to affect many other projects as well (I'm being lazy and
> > not  counting them right now)
> > 
> > Initially, the thinking was that moving the config options around
> > would
> > cause some breakage with projects outside of neutron, but that
> > would be
> > fine because projects shouldn't really be using neutron as a
> > library
> > and using it to register config options.  However, with these 3
> > patches, I definitely don't feel comfortable breaking the amount of
> > projects these would break.  It also makes me think that maybe
> > these
> > options should be in neutron-lib since they're consumed so widely.
> 
> Definitely not neutron-lib material (unless carefully hidden behind
> clearly  
> public API).
> 
> There is a reason why oslo folks explicitly deny any support for  
> configuration option names and locations their libraries expose
> [1].  
> Options are for operators to change in configuration files, but not
> to  
> access them or set programmatically. If there are options that
> subprojects  
> need access to, we should expose them via explicitly public API, like
> we  
> did with global_physnet_mtu [2].
> 
> [1]  
> http://docs.openstack.org/developer/oslo.config/faq.html#why-are-conf
> iguration-options-not-part-of-a-library-s-api
> [2]  
> https://github.com/openstack/neutron/blob/181bdb374fc0c944b1168f27ac7
> b5cbb0ff0f3c3/neutron/plugins/common/utils.py#L43

Yeah allowing the options to be imported directly from code outside the
repo doesn't make sense.  When you talk about a public API in neutron-
lib for these options, are only talking about READ access as the
example you gave? OR are you also talking about being able to register
these options as well via functions that require no access to the
options?  If that is the case, then these centralize config option
patches are basically doing that, except not in neutron-lib.  Do you
think we should move these to neutron-lib instead?  This would mean the
config options themselves would then probably end up living in neutron-
lib (though I guess they wouldn't have to).  We'll still have to figure
out what to do with the subprojects though, but having them in neutron-
lib and neutron at the same time during a transition period might make
this easier.

> 
> > Anyway, I've come up with some possible options to deal with this,
> > but
> > would like to hear others' opinions on this:
> > 
> > 1) Let the patches merge and break those projects as a signal that
> > importing these shouldn't be done.  The affected projects can
> > choose to
> > push fixes that continue importing the neutron config options or
> > defining their own config options.
> > 2) Deprecate the old locations for some timeframe, and then remove
> > later.
> > 3) Texas Three-Step: change the neutron patches to keep pointers in
> > the
> > old locations to the new, and then push patches to the affected
> > repos
> > with Depends-On directives.  Once all patches merge, push up one
> > more
> > patch to neutron to remove the old location.
> > 4) Abandon these reviews and do nothing.
> > 5) Move these config options to neutron-lib so that they can be
> > used by
> > any project.  This still requires doing one of the above options,
> > however.
> > 6) Any others I can't think of?
> 
> Whatever makes subprojects stop accessing neutron configuration
> options  
> programmatically. If we indeed identify something that plugins MUST
> have  
> access to, then let’s work in scope of neutron-lib to expose those
> options  
> through public API (not CONF object!)
> 
> I believe it's subprojects who should identify and vouch for and
> propose  
> neutron-lib patches to expose values they may need in their
> extensions;  
> Neutron should of course give a notice about its plans; we could
> broadly  
> target those changes to early Pike if we think it’s worth a
> postponement,  
> and start talking to subprojects about them driving readiness for
> the  
> changes during Ocata.

Makes sense.

> 
> Ihar
> 
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