[openstack-dev] [nova] changing old migrations is verboten

Sean Dague sean at dague.net
Fri Nov 1 17:31:49 UTC 2013


On 11/01/2013 12:20 PM, Johannes Erdfelt wrote:
<snip>
>> I've watched us mess this up multiple times in the past when we were
>> *sure* it was good. And as has been noticed recently, one of the
>> collapses changes a fk name (by accident), which broke upgrades to
>> havana for a whole class of people.
>>
>> So I think that we really should put a moratorium on touching past
>> migrations until there is some sort of automatic validation that the
>> new and old path are the same, with sufficiently complicated data
>> that pushes the limits of those fields.
>>
>> Manual inspection by one person that their environment looks fine
>> has never been a sufficient threshold for merging code.
> 
> I can get completely on board with that.
> 
> Does that mean you're softening your stance that migrations should never
> be touched?

If we have a way to automatically validate the new final results vs. the
old final results, including carrying interesting edge condition data
through it, yes, absolutely.

Many things move from "verboten" to "acceptable" with sufficient test
harness.

	-Sean

-- 
Sean Dague
http://dague.net

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