[Engine-devel] [RFC] ovirt-engine - vdc_config default options

[Alon Bar-Lev]

Hello Eli,

----- Original Message -----
> From: "Eli Mesika" <emesika at redhat.com>
> To: "Alon Bar-Lev" <alonbl at redhat.com>
> Cc: engine-devel at ovirt.org, "Livnat Peer" <lpeer at redhat.com>
> Sent: Wednesday, September 12, 2012 3:48:00 PM
> Subject: Re: [Engine-devel] [RFC] ovirt-engine - vdc_config default options
> 
> > > >>> QUESTIONS
> > > >>>
> > > >>> 1. Why do we store default values in database?
> 
> I wanted to add few important points
> a) We have default values in DB in order to enable overriding values
> in the 0000_config.sql file only if a customer did not change the
> default value, if a customer changed the default in some entries, we
> want to honour the customer settings

Default != value.
Default is what should be used if not specified explicitly 

Current implementation puts the default value as a value, so you cannot distinguish between what user enforced.

When a default is changed, because of field feedback, we should push this into the database instead of keeping in database only options that were modified by the user and fetch the default from the option metadata.

In another words.... there should be no 000_config.sql, the option table should be empty as long as the user does not modify any of the options.

> b)There may be other requirements on configuration that are easier to
> manage in the database, for example, I have heard that one of the
> suggested features regarding configuration is to keep a kind of
> configuration history and know exactly which configuration values
> was changed, when and by whom.

There is no conflict. You can have audit table when modifying options.
Keep in mind that I discuss the option metadata.
I believe you are discussing the option data.

> c) The version mechanism in the config is working like this : there
> is a 'general' version , means that this value is not version
> dependant, or the version can be a real version like 3.1 3.2 etc ,
> in such case the value is version dependant and an entry is required
> for each version.

Again, there is no conflict, as the default value within the metadata can be version specific too.

Having said that, I don't understand how two different versions can work with the different data models and share one database and options.

> I agree however, that the default value in the code is redundant and
> error prone and should be removed.

>From what you wrote above, I don't understand how you reached to this conclusion. Can you please explain?

Thanks,
Alon.