Hayes, Graham wrote:
On 18/07/16 22:27, Ronald Bradford wrote:
Hi All,
For Oslo libraries we ensure that API's are backward compatible for 1+ releases.
When an Oslo API adds a new class attribute (as in this example of
is_admin_project and 4 other attributes) added to Oslo Context in
2.6.0, these are added to ensure this API is also forward compatible
with existing project code for any contract with the base class
instantiation or manipulation.
Which projects is this run against?
The issue seen is presently Nova specific (as other projects can
utilize 2.6.0) and it is related to projects that sub-class
oslo.context, and how unit tests are written for using class
parameters. Ideally, to implement using oslo.context correctly
OpenStack projects should:
Designate also had to make a quick change to support 2.6.0.
We were lucky as it was noticed by the RDO builds, which had pulled in
2.6.0 before the requirements update was proposed, so it did not break
our gate.
I just did a quick search and there is a few projects that hardcoded
this, like we did.
Ya, that's bad, nothing in the docs of the to_dict API say what to even
compare against (or the keys produced), so I'm pretty sure anyone doing
this is setting themselves up for future failure and fragile software.
* Not perform direct dictionary to dictionary comparisons with the
to_dict() method as this does not support when new attributes at
added. Two patches (one to nova) address this in offending projects
[5][6]
* Unit tests should focus on attributes specific to the sub-classed
signature, e.g. [7]. Oslo context provides an extensive set of unit
tests for base class functionality. This is a wish list item for
projects to implement.
The to_dict() method exists as a convenience method only and is not an
API contract. The resulting set of keys should be used accordingly.
This is why there is no major release version.
How are developers supposed to know that?
So we (in oslo) can (and ideally will) make this better but when the API
doesn't itself tell you what keys are produced or what the values of
those keys are then it should be pretty obvious to u (the library user)
that u can not reliably do dictionary comparisons (because how do u know
what to compare against when the docs don't state that?). I suppose
people are 'reverse engineering the dict' by just looking at the code
but that's also not so great...
This kind of feels like semantics. This was an external API that changed
and as a result should have been a major version.
I think this is where it gets a little bit into as u said, semantics,
but the semantics IMHO are important here because it affects the ability
of oslo.context to move forward & change.
I suppose we should/could just put a warning on this method like I did
in taskflow (for something similar) @
https://github.com/openstack/taskflow/blob/master/taskflow/engines/base.py#L71
to denote that nothing in the dict that is returned can be guaranteed to
always be the same.
There is a note from our discussion in Oslo to improve our
documentation to describe the API use of to_dict() better and state we
will not remove to_dict() keys within a release, but that may happen
between releases.
There is a subsequent problem with how Nova performs a warning test
[8]. Additional reviews are looking at addressing this sub-class usage
of from_dict() and to_dict().
Regards
Ronald
[5] https://review.openstack.org/#/c/343694/,
[6] https://review.openstack.org/#/c/342367/
[7] https://review.openstack.org/#/c/342869/
[8]
http://git.openstack.org/cgit/openstack/nova/tree/nova/tests/unit/test_context.py#n144
On Mon, Jul 18, 2016 at 10:50 AM, Matt Riedemann
<[email protected]> wrote:
On 7/18/2016 9:42 AM, Matt Riedemann wrote:
On 7/18/2016 9:09 AM, Markus Zoeller wrote:
Since yesterday, Nova uses "oslo.context" 2.6.0 [1] but the needed
change [2] is not yet in place, which broke "gate-nova-python27-db"[3].
Logstash counts 70 hits/h [4]. Most folks will be at the midcycle in
Portland and won't be available for the next 2h or so.
If you can have a look at it and merge it, that would be great.
References:
[1]
https://github.com/openstack/requirements/commit/238389c4ee1bd3cc9be4931dd2639aea2dae70f1
[2] https://review.openstack.org/#/c/342604/1
[3] https://bugs.launchpad.net/nova/+bug/1603979
[4] logstash: http://goo.gl/79yFb9
This is an API change for oslo.context, why wasn't it released as 3.0.0?
Seems we should revert the upper-constraints bump and blacklist 2.6.0,
then get that released as 3.0.0.
Here is the blacklist:
https://review.openstack.org/#/c/343683/
--
Thanks,
Matt Riedemann
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