[openstack-dev] When to revert a patch?

Morgan Fainberg morgan.fainberg at gmail.com
Fri Mar 4 15:24:51 UTC 2016

On Mar 4, 2016 10:16, "Monty Taylor" <mordred at inaugust.com> wrote:
> On 03/04/2016 08:37 AM, Ruby Loo wrote:
>> Hijacked from ' [openstack-dev] [ironic] Remember to follow RFE process'
>> thread:
>>         > Should we revert the patch [1] for now? (Disclaimer. I haven't
looked at the
>>         > patch itself. But I don't think I should have to, to know what
the API
>>         > change is.)
>>         >
>>         Thanks for calling it out Ruby, that's unfortunate that the
>>         patch was
>>         merged without the RFE being approved. About reverting the patch
>>         think we shouldn't do that now because the patch is touching the
>>         and introducing a new microversion to it.
>>     Exactly. I've -2'ed the revert, as removing API version is even
>>     worse than landing a change without an RFE approved. Let us make
>>     sure to approve RFE asap, and then adjust the code according to it.
>> This brings up another issue, which I recall discussing before. Did we
>> decide that we'd never revert something that touches the
>> API/microversion? It might be good to have guidelines on this if we
>> don't already. IF the API is incorrect? If the API could be improved? If
>> the API was only in master for eg 48 hours?
> I believe you need to treat master as if it's deployed to production. So
once an API change is released, 'fixing' it needs to be done like any other
API change - with a microversion bump and appropriate backwards compat.
> (For instance, I have a CI/CD pipeline merging from master every hour and
doing a deploy - so 48 hours is a long time ago)
> Monty

So let me jump in here and add in that a direct revert only should happen
in extreme circumstances: aka a change that breaks behavior without a micro
version bump - or something that is causing a break that cannot be fixed
easily rolling forward. (Unable to land code in the gate at all for
example, including roll forward fixes)

In general (and especially with microversions) fail and fix moving forward
is much better for the end users/deployers especially since folks are doing
CD more aggressively now.

There are other considerations but a revert really is one of the most
extreme responses and should be used sparingly.

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