[openstack-dev] [all][oslo] config generator default overrides and namespaces

Doug Hellmann doug at doughellmann.com
Fri Mar 11 21:01:44 UTC 2016

rbradford found an issue in neutron today with the entry point for
declaring overrides for defaults for options coming from the cors
middleware. We then subsequently found the same problem in a bunch of
other projects, and have submitted patches to fix them [1]. krotscheck
is reviewing the pending patches to update those before the bad values
land [2].

The tl;dr is: Do not name things in your project using names coming
from other projects.

In this case, the entry points were named 'oslo.middleware.cors'
instead of '$project' and so when the config generator was run on
a system with all projects installed, all of the default override
functions were being invoked because all versions of the
oslo.middleware.cors entry point were loaded. As a result, some
incompatible code was being imported, causing an exception, and so
the sample file generation for solum failed with a traceback in
neutron code. Weird.

If you end up with one of the patches in your project, please assign it
high review priority but look at it carefully before merging to make
sure I picked a valid name.

If you are using this feature in some other way, please check the
names you're using for the entry points to ensure that they have
the application name in them somewhere, and do not refer directly
to the name of a library managed by another team or shared between

I have updated the oslo.config documentation to be more clear about
this naming restriction [3].


[1] https://review.openstack.org/#/q/topic:fix-config-default
[2] https://review.openstack.org/#/q/branch:master+topic:bug/1551836
[3] https://review.openstack.org/#/c/291904/

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