[openstack-dev] [nova] minimum review period for functional changes that break backwards compatibility

Sean Dague sean at dague.net
Sun Dec 29 13:04:08 UTC 2013

On 12/29/2013 03:06 AM, Day, Phil wrote:
>> Basically, I'm not sure what problem you're trying to solve - lets tease that
>> out, and then talk about how to solve it. "Backwards incompatible change
>> landed" might be the problem - but since every reviewer knew it, having a
>> longer review period is clearly not connected to solving the problem :).
> That assumes that a longer review period wouldn't of allowed more reviewers to provide input - and I'm arguing the opposite.   I also think that some clear guidelines might have led to the core reviewers holding this up for longer.   As I said in my original post, the intent to get more input was clear in the reviews, but the period wasn't IMO long enough to make sure all the folks who may have something to contribute could.   I'd rather see some established guidelines than have to be constantly on the lookout for changes every day or so and hoping to catch them in time.

Honestly, there are currently 397 open reviews in Nova. I am not 
convinced that waiting on this one would have come up with a better 
decision. I'll given an alternative point of view of the graceful 
shutdown patch, where we sat on that for months, had many iterations, 
landed it, it added 25 minutes to all the test runs (which had been 
hinted at sometime in month 2 of the review, but got lots in the mists 
of time), and we had to revert it.

I'm not convinced more time brings more wisdom. We did take it to the 
list, and there were no objections. I did tell Robert to wait because I 
wanted to get those points of view. But they didn't show up. Because it 
was holidays could we have waited longer? Sure. I'll take a bad on that 
in feeling that Dec 19th wasn't really holidays yet because I was still 
working. :) But, honestly, given no negative feedback on the thread in 
question and no -1 on the review, the fact that folks like google 
skipped ext3 entirely, means this review was probably landing regardless.

Every time we need to do a revert, we need to figure out how to catch it 
the next time. "Humans be better" is really not a solution. So this 
sounds like we need a guest compatibility test where we boot a ton of 
different guests on each commit and make sure they all work. I'd whole 
heartily support getting that in if someone wants to champion that. 
That's really going to be the only way we have a systematic way of 
knowing that we break SLES in the future.

So the net, we're all human, and sometimes make mistakes. I don't think 
we're going to fix this with review policy changes, but we could with 
actual CI enhancements.


Sean Dague
Samsung Research America
sean at dague.net / sean.dague at samsung.com

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