[openstack-dev] [Nova] Frustrations with review wait times

Robert Collins robertc at robertcollins.net
Wed Aug 28 10:29:23 UTC 2013

On 28 August 2013 21:13, Daniel P. Berrange <berrange at redhat.com> wrote:
> On Wed, Aug 28, 2013 at 03:43:21AM +0000, Joshua Harlow wrote:

>> For a big project like nova the workload could be spread out more
>> like that.
> I don't think any kind of rotation system like that is really
> practical. Core team members need to have the flexibility to balance
> their various conflicting workloads in a way that maximises their
> own productivity.

So does everyone else, surely? Are you saying 'I don't think I can
commit to regular reviewing', or are you saying 'all reviewers will be
unable to commit to regular reviewing'? Or something else?

There are what - 300? ATC's for nova, and 20 core *reviewers*.

(taking 90 days to avoid some of the peak bulge).

Total reviews: 11327 (6311 by core)
Total reviewers: 290

Thats 125 reviews a day, or 6 per core reviewer, if core reviewers did
every single review. Or 3 reviews a day at the moment. Adjusting up by
2/7 to cover weekends thats 8 per day if core did every review, and 4
per day for the ones they actually did over that period.

Say it takes 20m to do a good review; thats 2.5 hours, more or less.
Thats daily - thats certainly a large enough time period that I can
see a rotation being potentially useful, for folk that need to discuss
their patch in realtime (to reduce roundtrips etc - I think everyone
knows how useful that can be).

Separately, look at the math - if we assume that core reviewers are
twice as productive within Nova due to familiarity with more code, we
can expect at most 40 peoples worth of contributions from nova-core,
vs 280 odd from ~nova-core, all other things things being equal. If
reviewing is (say) 1/10th the time of writing the code, then 260
contributors would create a review load that can fully saturate 52
reviewers (/10 * 2 for the two +2s).

Are we there yet? Arguably yes - there are lots of active reviewers
doing as many reviews as most of the core team. And it's taking a week
to review things at the moment, which means plenty of time for things
to change under the patch and actually cause more review work due to
rework. OTOH those are very coarse numbers with lots of assumptions.
My main point is that scaling Nova development is hard, the problems
are real, and right now it's a significant time investment needed for
anyone wanting to become a core reviewer.


Robert Collins <rbtcollins at hp.com>
Distinguished Technologist
HP Converged Cloud

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