Hi,

Just a heads up that the latest version of dogpile (0.7.0 onwards)
have become incompatible with oslo.cache. This is causing a few
issues for jobs. It's a little complex due to functional code and many decorated functions.

The error you will see is:

oslo_cache.tests.test_cache.CacheRegionTest.test_function_key_generator_with_kwargs
-----------------------------------------------------------------------------------

Captured traceback:
~~~~~~~~~~~~~~~~~~~
    b'Traceback (most recent call last):'
    b' File "/tmp/oslo.cache/oslo_cache/tests/test_cache.py", line 324, in test_function_key_generator_with_kwargs'
    b' value=self.test_value)'
    b' File "/tmp/oslo.cache/.tox/py37/lib/python3.7/site-packages/testtools/testcase.py", line 485, in assertRaises'
    b' self.assertThat(our_callable, matcher)'
    b' File "/tmp/oslo.cache/.tox/py37/lib/python3.7/site-packages/testtools/testcase.py", line 498, in assertThat'
    b' raise mismatch_error'
    b'testtools.matchers._impl.MismatchError: <function CacheRegionTest._get_cacheable_function.<locals>.cacheable_function at 0x7fec3f795400> returned <oslo_cache.tests.test_cache.TestProxyValue object at 0x7fec3f792550>'

The problem appear since we uncap dogpile.cache on oslo.cache: https://github.com/openstack/oslo.cache/commit/62b53099861134859482656dc92db81243b88bd9

The following unit test fail since we uncap dogpile => https://github.com/openstack/oslo.cache/blob/master/oslo_cache/tests/test_cache.py#L318

The problem was introduced by: https://gerrit.sqlalchemy.org/#/c/sqlalchemy/dogpile.cache/+/996/

Your main issue on oslo.cache side is that keyword arguments are tranformed in positionnal arguments when we use dogpile.cache.region.cache_on_arguments.

I've try to revert the changes introduced by the previous dogpile.cache change and everything works fine on the oslo.cache side when changes was reverted (reverted to revision https://github.com/sqlalchemy/dogpile.cache/blob/2762ada1f5e43075494d91c512f7c1ec68907258/dogpile/cache/region.py).

The expected behavior is that dogpile.cache.util.function_key_generator raise a ValueError if **kwargs founds, but our kwargs is empty and our `value=self.test_value was` is recognized as a positionnal argument.
Our unit test looking for an assertRaise(ValueError) on cachable decorated function when we pass kwargs but it doesn't happen due to empty kwargs.

For these reasons we guess that is an dogpile.cache issue and not an oslo.cache issue due to the changes introduced by `decorator` module.

The following are related:

- https://github.com/openstack/oslo.cache/blob/master/oslo_cache/tests/test_cache.py#L318 : unit test where the problem occure

- https://review.openstack.org/#/c/638788/ : possible fix but we don't think that is the right way

- https://review.openstack.org/#/c/638732/ : possible remove of the unit test who fail

The issue is being tracked in:

https://bugs.launchpad.net/oslo.cache/+bug/1817032

If some dogpile expert can take a look and send feedback on this thread you are welcome.

Thanks,

--

Hervé Beraud

Senior Software Engineer

Red Hat - Openstack Oslo

irc: hberaud