Open Stack

Doug,


On Wed, Nov 13, 2013 at 9:49 PM, Doug Hellmann
<doug.hellmann at dreamhost.com>wrote:

>
>
>
> On Mon, Nov 11, 2013 at 6:08 PM, Mark McLoughlin <markmc at redhat.com>wrote:
>
>>
>> One thing worth trying would be to encode the validation rules in the
>> config option declaration.
>>
>> Some rules could be straightforward, like:
>>
>> opts = [
>>   StrOpt('foo_url',
>>          validate_rule=cfg.MatchesRegexp('(git|http)://')),
>> ]
>>
>> but the rule you describe is more complex e.g.
>>
>> def validate_proxy_url(conf, group, key, value):
>>     if not conf.vnc_enabled:
>>         return
>>     if conf.ssl_only and value.startswith("http://"):
>>         raise ValueError('ssl_only option detected, but ...')
>>
>> opts = [
>>   StrOpt('novncproxy_base_url',
>>          validate_rule=validate_proxy_url),
>>   ...
>> ]
>>
>> I'm not sure I love this yet, but it's worth experimenting with.
>>
>
> One thing to keep in mind with the move to calling register_opt() at
> runtime instead of import time is the service may run for a little while
> before it reaches the point in the code where the option validation code is
> triggered. So I like the idea, but we may want a shortcut for validation.
>
> We could add a small app to oslo.config that will load the options in the
> same way the conf generator and doc tool will, but then also read the
> configuration file and perform the validation.
>

We implement similar approach in Rubick [1]. Collector script generates
configuration schema from code [2], while generator script [3] allows to
have different versions of configuration schema:

[1] https://github.com/MirantisLabs/rubick/tree/master/rubick/schemas
[2]
https://github.com/MirantisLabs/rubick/blob/master/rubick/schemas/collector.py#L189
[3]
https://github.com/MirantisLabs/rubick/blob/master/rubick/schemas/generator.py

I think it would be useful to discuss pros and cons of contributing parts
of this code to oslo.config.

--
Best regards,
Oleg Gelbukh
Mirantis Labs
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