[openstack-dev] [oslo][cinder][nova][neutron] going forward to oslo-config-generator ...

Gary Kotton gkotton at vmware.com
Sat Mar 21 16:36:07 UTC 2015

One of the issues that we had in Nova was that when we moved to oslo
libraries configuration options support by the libraries were no longer
present in the generated configuration file. Is this something that is
already supported or planned (sorry for being a little ignorant here).
In neutron things may be a little more challenging as there are many
different plugins and with the decomposition things may have additional
challenges. The configuration binding is done via the external decomposed
code and not in the neutron code base. So it is not clear how that code
may be parsed to generate the sample configuration.

On 3/21/15, 12:01 AM, "Jay S. Bryant" <jsbryant at electronicjungle.net>

>Let me start with the TLDR;
>Cinder, Nova and Neutron have lots of configuration options that need to
>be processed by oslo-config-generator to create the
><project>.conf.sample file.  There are a couple of different ways this
>could be done.  I have one proposal out, which has raised concerns,
>there is a second approach that could be taken which I am proposing
>below.  Please read on if you have a strong opinion on the precedent we
>will try to set in Cinder.  :-)
>We discussed in the oslo meeting a couple of weeks ago a plan for how
>Cinder was going to blaze a trail to the new oslo-config-generator.  The
>result of that discussion and work is here:  [1]  It needs some more
>work but has the bare bones pieces there to move to using
>With the change I have written extensive hacking checks that ensure that
>any lists that are registered with register_opts() are included in the
>base cinder/opts.py file that is then a single entry point that pulls
>all of the options together to generate the cinder.conf.sample file.
>This has raised concern, however, that whenever a developer adds a new
>list of configuration options, they are going to have to know to go back
>to cinder/opts.py and add their module and option list there.  The
>hacking check should catch this before code is submitted, but we are
>possibly setting ourselves up for cases where the patch will fail in the
>gate because updates are not made in all the correct places and because
>pep8 isn't run before the patch is pushed.
>It is important to note, that this will not happen every time a
>configuration option is changed or added, as was the case with the old
>check-uptodate.sh script.  Only when a new list of configuration options
>is added which is a much less likely occurrence.  To avoid this
>happening at all it was proposed by the Cinder team that we use the code
>I wrote for the hacking checks to dynamically go through the files and
>create cinder/opts.py whenever 'tox -egenconfig' is run.  Doing this
>makes me uncomfortable as it is not consistent with anything else I am
>familiar with in OpenStack and is not consistent with what other
>projects are doing to handle this problem.  In discussion with Doug
>Hellman, the approach also seemed to cause him concern.  So, I don't
>believe that is the right solution.
>An alternative that may be a better solution was proposed by Doug:
>We could even further reduce the occurrence of such issues by moving the
>list_opts() function down into each driver and have an entry point for
>oslo.config.opts in setup.cfg for each of the drivers.  As with the
>currently proposed solution, the developer doesn't have to edit a top
>level file for a new configuration option.  This solution adds that the
>developer doesn't have to edit a top level file to add a new
>configuration item list to their driver.  With this approach the change
>would happen in the driver's list_opts() function, rather than in
>cinder/opts.py .  The only time that setup.cfg would needed to edited is
>when a new package is added or when a new driver is added.  This would
>reduce some of the already minimal burden on the developer.  We,
>however, would need to agree upon some method for aggregating together
>the options lists on a per package (i.e. cinder.scheduler, cinder.api)
>level.  This approach, however, also has the advantage of providing a
>better indication in the sample config file of where the options are
>coming from.  That is an improvement over what I have currently proposed.
>Does Doug's proposal sound more agreeable to everyone?  It is important
>to note that the fact that some manual intervention is required to
>'plumb' in the new configuration options was done by design.  There is a
>little more work required to make options available to
>oslo-config-generator but the ability to use different namespaces,
>different sample configs, etc were added with the new generator.  These
>additional capabilities were requested by other projects.  So, moving to
>this design does have the potential for more long-term gain.
>Thanks for taking the time to consider this!
>[1] https://review.openstack.org/#/c/165431/
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