Open Stack

Hi,

I sent the following mail when action=clear was discussed.
My concern is that "clear" (reset to the default) and "no-<param_name>"
have different meaning in some case. A good example is gateway_ip.

I agree we should have better usability and maintainability.

------------------------------------------------------------
During the review https://review.openstack.org/#/c/18018/,
A question on the API layer has been raised: What is the meaning of 'None'?

In the review a problem that a meaning of passing 'None' in Quantum API
(action=clear) for an attribute is ambiguous has been raised.
A word "clear" is used in two meanings: (a) to set an empty value,
and (b) to reset to default.

These are similar in many cases, but they have different meanings.
For example, let's assume attribute X is a list and its default value is [1,2].
"Setting an empty value" means that [] is set to X, and "reseting to default"
means that [1,2] is set to X.

I believe these two should be distinguished on the API layer.
The API layer shoule provide:
- a way to set an empty value (e.g., "", [], {}), and
- a way to reset to its default value

IMO, the former is innevitable since the API should not limit a value which
is valid for a specific attribute, and the latter is very useful if supported.
------------------------------------------------------------

>>>>> Date: Fri, 8 Feb 2013 18:55:14 +0000
>>>>> From: Salvatore Orlando <sorlando at nicira.com>
>>>>> Subject: Re: [openstack-dev] [quantum][CLI]Specifying None values toattributes.
> 
> This is an important usability topic with have fallen a bit behind.
> I recall Gary's proposal around an explicit 'clear' action, and I
> remember Yong also has a patch for it.
> 
> I don't remember whether there was consensus on it; my concern was
> just that from an usability and maintainability perspective probably
> we can do better (what would be the possible actions beyond clearing
> and setting it, where setting is achieved with an '='?, also I
> generally tend to refrain from using magic values, because they always
> caused me more pain than gain in the past).
> 
> Actually, we already do this through the CLI, although in a fairly
> hardcoded way.
> We can set a gateway_ip to null for a subnet with the --no-gateway option;
> we can also remove the external gateway for a router with the
> router-gateway-clear command.
> I would cast my vote for allowing the CLI to add a --no-<param_name>
> option for all the parameters that can be cleared.
> Another options that can be considered stems from CLI tools like
> ovs-vsctl or xe.
> 
> with ovs-vsctl I can nullify a OVS DB entry with ovs-vsctl clear
> <table> <record> <column>
> with xe I can nullify a parameter with xe <resource>-param-clear <param_name>
> 
> For instance we could do:
> quantum subnet-update <subnet_id> --clear gateway_ip
> or
> quantum router-update <router_id> --clear external_network_info
> 
> NOTE: I'm not advocating changes to CLI for existing commands; this is
> just an example.
> 
> Salvatore
> 
> 
> On 8 February 2013 18:10, Dan Wendlandt <dan at nicira.com> wrote:
> >
> >
> > On Fri, Feb 8, 2013 at 7:10 AM, Roman Prykhodchenko
> > <rprikhodchenko at mirantis.com> wrote:
> >>
> >> I assume I should ping the community again about this issue. Does anyone
> >> have any thought on this?
> >
> >
> > Hi Roman,
> >
> > Sorry, I think people on the team a bit overwhelmed with reviews + the G-3
> > deadline, and are probably behind on general list email.
> >
> > I agree that this is a general problem.  Yong, Mark, and Salvatore are
> > probably the most relevant people to answer this question, as I'm not up to
> > date on these client / API discussions.  I'll ping them and encourage them
> > to comment on-list.
> >
> > Dan
> >
> >
> >
> >>
> >>
> >>
> >> - Roman
> >>
> >>
> >> On Tue, Feb 5, 2013 at 1:24 PM, Roman Prykhodchenko
> >> <rprikhodchenko at mirantis.com> wrote:
> >>>
> >>> Hi folks!
> >>>
> >>> Recently I implemented a patch that allows resetting session persistence
> >>> for a VIP: https://review.openstack.org/#/c/20725/.
> >>> What I noticed is that it's not possible to use this feature from the
> >>> command line. The problem seems to be quite general because there's no way
> >>> of specifying None values for attributes.
> >>>
> >>> As some of you noticed in the review Yong (gongysh) has made some changes
> >>> that allow to specify action=clear in the quantum-client's shell and that
> >>> will send a None value: https://review.openstack.org/#/c/17436/.
> >>> Unfortunately that change is abandoned right now because we didn't came up
> >>> with a consensus about dealing with None values in command line environment.
> >>>
> >>> I think it's reasonable to re-initiate this discussion because specifying
> >>> None values from the command line is quite a necessary thing now and it
> >>> needs a generic solution.
> >>>
> >>>
> >>> - Roman
> >>>
> >>
> >>
> >> _______________________________________________
> >> OpenStack-dev mailing list
> >> OpenStack-dev at lists.openstack.org
> >> http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev
> >>
> >
> >
> >
> > --
> > ~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > Dan Wendlandt
> > Nicira, Inc: www.nicira.com
> > twitter: danwendlandt
> > ~~~~~~~~~~~~~~~~~~~~~~~~~~~
> >
> > _______________________________________________
> > OpenStack-dev mailing list
> > OpenStack-dev at lists.openstack.org
> > http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev
> >
> 
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