On 14 March 2017 at 10:21, lương hữu tuấn <tuantulu...@gmail.com> wrote:
> > > On Tue, Mar 14, 2017 at 10:28 AM, Dougal Matthews <dou...@redhat.com> > wrote: > >> >> >> On 13 March 2017 at 09:49, lương hữu tuấn <tuantulu...@gmail.com> wrote: >> >>> >>> >>> On Mon, Mar 13, 2017 at 9:34 AM, Thomas Herve <the...@redhat.com> wrote: >>> >>>> On Fri, Mar 10, 2017 at 9:52 PM, Ryan Brady <rbr...@redhat.com> wrote: >>>> > >>>> > One of the pain points for me as an action developer is the OpenStack >>>> > actions[1]. Since they all use the same method name to retrieve the >>>> > underlying client, you cannot simply inherit from more than one so >>>> you are >>>> > forced to rewrite the client access methods. We saw this in creating >>>> > actions for TripleO[2]. In the base action in TripleO, we have >>>> actions that >>>> > make calls to more than one OpenStack client and so we end up >>>> re-writing and >>>> > maintaining code. IMO the idea of using multiple inheritance there >>>> would be >>>> > helpful. It may not require the mixin approach here, but rather a >>>> design >>>> > change in the generator to ensure the method names don't match. >>>> >>>> Is there any reason why those methods aren't functions? AFAICT they >>>> don't use the instance, they could live top level in the action module >>>> and be accessible by all actions. If you can avoid multiple >>>> inheritance (or inheritance!) you'll simplify the design. You could >>>> also do client = NovaAction().get_client() in your own action (if >>>> get_client was a public method). >>>> >>>> -- >>>> Thomas >>>> >>>> If you want to do that, you need to change the whole structure of base >>> action and the whole way of creating an action >>> as you have described and IMHO, i myself do not like this idea: >>> >>> 1. Mistral is working well (at the standpoint of creating action) and >>> changing it is not a short term work. >>> 2. Using base class to create base action is actually a good idea in >>> order to control and make easy to action developers. >>> The base class will define the whole mechanism to execute an action, >>> developers do not need to take care of it, just only >>> providing OpenStack clients (the _create_client() method). >>> 3. From the #2 point of view, the alternative to >>> NovaAction().get_client() does not make sense since the problem here is >>> subclass mechanism, >>> not the way to call get_client(). >>> >> > Hi, > > It is hard to me to understand what Thomas wants to say but i just > understood based on what he wrote:). Sorry for my misunderstanding. > > >> I might be wrong, but I think you read that Thomas wants to use functions >> for actions, not classes. I don't think that is the case. I think he is >> referring to the get_client method which is also what rbrady is referring >> to. At the moment multiple inheritance wont work if you want to inherit >> from NovaAction and KeyStone action because they both provide a >> "_get_client" method. If they has a unique name "get_keystone_client" and >> "get_nova_client" then the multiple inheritance wouldn't clash. >> >> Sorry Dougal but i do not get your point. Why the get_client could not be > used through instance since it has context? > In Mistral we have various OpenStack action classes. For example NovaAction[1] and GlanceAction[2] (and many others in that file). If I want to write an action that uses either Nova or Glance I can inherit from them, for example: class MyNovaAction(NovaAction): def run(self): client = self._create_client() # ... do something with the client and return However, if I wanted to use use two OpenStack clients, which I admit is a special case and I think one that only TripleO uses (that we know of). class MyNovaAndGlanceActioin(NovaAction, GlanceAction): def run(self): nova = self._create_client() glance = self._create_client() <- doesn't work because they both access the same method on NovaAction. If the method was called "create_nova_client" and "create_glance_client" then you could inherit from both without any conflict. However, based on the reply Thomas sent earlier, I think we should consider something like this when the OpenStack actions are moved to mistral-extra. nova = NovaAction.client(context) This is slight adaptation changes "_create_client" to "client" and makes it a class method that accepts the context. I think this would provide a very clear interface. I also can't think of any advantage of inheriting from NovaAction, there is no state shared with it, so we only want it to create the class for us. [1]: https://github.com/openstack/mistral/blob/master/mistral/actions/openstack/actions.py#L75 [2]: https://github.com/openstack/mistral/blob/master/mistral/actions/openstack/actions.py#L109 > > > >> Thomas - The difficulty with these methods is that they need to access >> the context - the context is going to be added to the action class, and >> thus while the get_client methods don't use the instance now, they will >> soon - unless we change direction. >> >> >> >>> @Renat: I myself not against to multiple inheritance too, the only thing >>> is if we want to make it multiple inheritance, we should think about it >>> more thoroughly for the hierarchy of inheritance, what each inheritance >>> layer does, etc. These work will make the multiple inheritance easy to >>> understand and for action developers as well easy to develop. So, IMHO, i >>> vote for make it simple, easy to understand first (if you continue with >>> mistral-lib) and then do the next thing later. >>> >>> Br, >>> >>> Tuan/Nokia >>> >>>> ____________________________________________________________ >>>> ______________ >>>> OpenStack Development Mailing List (not for usage questions) >>>> Unsubscribe: openstack-dev-requ...@lists.op >>>> enstack.org?subject:unsubscribe >>>> http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev >>>> >>> >>> >>> ____________________________________________________________ >>> ______________ >>> OpenStack Development Mailing List (not for usage questions) >>> Unsubscribe: openstack-dev-requ...@lists.op >>> enstack.org?subject:unsubscribe >>> http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev >>> >>> >> >> ____________________________________________________________ >> ______________ >> OpenStack Development Mailing List (not for usage questions) >> Unsubscribe: openstack-dev-requ...@lists.openstack.org?subject:unsubscrib >> e >> http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev >> >> > > __________________________________________________________________________ > OpenStack Development Mailing List (not for usage questions) > Unsubscribe: openstack-dev-requ...@lists.openstack.org?subject:unsubscribe > http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev > >
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