[openstack-dev] [Nova][Oslo.cfg] Configuration string substitution

Radoslav Gerganov rgerganov at vmware.com
Fri Jun 20 08:48:26 UTC 2014


Hi,

> On Wed, Jun 18, 2014 at 4:47 AM, Gary Kotton <gkotton at vmware.com> wrote:
> > Hi,
> > I have encountered a problem with string substitution with the nova
> > configuration file. The motivation was to move all of the glance settings
> > to
> > their own section (https://review.openstack.org/#/c/100567/). The
> > glance_api_servers had default setting that uses the current glance_host
> > and
> > the glance port. This is a problem when we move to the ‘glance’ section.
> > First and foremost I think that we need to decide on how we should denote
> > the string substitutions for group variables and then we can dive into
> > implementation details. Does anyone have any thoughts on this?
> > My thinking is that when we use we should use a format of $<group>.<key>.
> > An
> > example is below.
> >
> 
> Do we need to set the variable off somehow to allow substitutions that
> need the literal '.' after a variable? How often is that likely to
> come up?

I would suggest to introduce a different form of placeholder for this like:

  default=['${glance.host}:${glance.port}']

similar to how variable substitutions are handled in Bash.  IMO, this is more readable and easier to parse.

-Rado



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