[ovirt-devel] [rhev-tech] Correct way to import hooking?

[Piotr Kliczewski]

On Sat, Nov 25, 2017 at 1:56 AM, Nir Soffer <nsoffer at redhat.com> wrote:
> On Fri, Nov 24, 2017 at 5:34 PM Piotr Kliczewski
> <piotr.kliczewski at gmail.com> wrote:
>>
>> On Fri, Nov 24, 2017 at 4:00 PM, Piotr Kliczewski
>> <piotr.kliczewski at gmail.com> wrote:
>> > On Fri, Nov 24, 2017 at 2:20 PM, Nir Soffer <nsoffer at redhat.com> wrote:
>> >> Adding devel at ovirt, the proper mailing list
>> >>
>> >> בתאריך יום ו׳, 24 בנוב׳ 2017, 7:42, מאת Germano Veit Michel
>> >> ‏<germano at redhat.com>:
>> >>>
>> >>> Hi,
>> >>>
>> >>> I'm trying to write a test for a hook. The test will fail if the hook
>> >>> does
>> >>> "import hooking", which seems to be the norm for vdsm hooks.
>> >>>
>> >>> [vdsm_hooks]$ grep -rn "import hooking" | wc -l
>> >>> 55
>> >>>
>> >>> Not sure if I'm doing something wrong, but it looks like I would need
>> >>> vdsm
>> >>> installed on my development machine in order for this import to work.
>> >>>
>> >>> ======================================================================
>> >>> ERROR: test suite for <class
>> >>> 'virttests.boot_hostdev_test.BootHostdevHookTests'>
>> >>> ----------------------------------------------------------------------
>> >>> Traceback (most recent call last):
>> >>>   File "/usr/lib/python2.7/site-packages/nose/suite.py", line 209, in
>> >>> run
>> >>>     self.setUp()
>> >>>   File "/usr/lib/python2.7/site-packages/nose/suite.py", line 292, in
>> >>> setUp
>> >>>     self.setupContext(ancestor)
>> >>>   File "/usr/lib/python2.7/site-packages/nose/suite.py", line 315, in
>> >>> setupContext
>> >>>     try_run(context, names)
>> >>>   File "/usr/lib/python2.7/site-packages/nose/util.py", line 471, in
>> >>> try_run
>> >>>     return func()
>> >>>   File
>> >>>
>> >>> "/home/gveitmic/Source/upstream/vdsm/tests/virttests/boot_hostdev_test.py",
>> >>> line 127, in setUpClass
>> >>>     import before_vm_start as boot_hostdev_hook
>> >>>   File "../vdsm_hooks/boot_hostdev/before_vm_start.py", line 24, in
>> >>> <module>
>> >>>     import hooking
>> >>> ImportError: No module named hooking
>
>
> This is expected, hooking is not install in the pyhton path by default.
>
> All the hooks are using wrong import. Vdsm is "fixing" the bad
> import by modifying the python path.
>
>>
>> >>>
>> >>> I can make it go away by using this in my hook:
>> >>>
>> >>> from vdsm.hook import hooking
>
>
> This is correct import - I would use this.
>
>>
>> >>>
>> >>> Then the test succeeds fine. But then I see all hooks use "import
>> >>> hooking"
>> >>> instead of "from vdsm.hook import hooking".
>> >>>
>> >>> [vdsm_hooks]$ grep -rn "from vdsm.hook import hooking" | wc -l
>> >>> 0
>> >>>
>> >>> Am I doing something wrong? Can someone put a light here? What is the
>> >>> correct way to do this import?
>> >
>> > Our approach for it is to modify PYTHONPATH [1] where we add vdsm.hook.
>> > It looks like we do not have similar update in [2] - script which run
>> > the tests.
>> >
>> > I will push a patch to fix it.
>>
>> https://gerrit.ovirt.org/#/c/84638/
>>
>> Please check whether it would work for you now.
>
>
> This can be handy for testing legacy hooks, but I think we should
> fix the imports instead, so no manipulation of python path is needed.
>

I agree that the path is not perfect way of doing it. I would love to fix it but
please note that people use `import hooking` in their own custom hooks
and we are unable to change them. This means that we won't be able to
fix it easily if ever. Because of that I am not sure whether it is good idea to
introduce different way of importing the module.

Till now we haven't had hook tests so the module was not available on the path.

>>
>>
>> >
>> > [1] https://github.com/oVirt/vdsm/blob/master/lib/vdsm/hooks.py#L98
>> > [2]
>> > https://github.com/oVirt/vdsm/blob/master/tests/run_tests_local.sh.in#L21
>> >
>> >>>
>> >>> Thanks,
>> >>> Germano
>> >>
>> >>
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