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[nova] Rebuild from cell0 limitation for personality files


On 04/10/2019 11:30 AM, Matt Riedemann wrote:
> I wanted to get some wider attention on what I think will be a 
> limitation in the rebuild from cell0 spec [1]. The main idea in that 
> spec is the user tries to create a server which fails during scheduling 
> to find a host and puts the instance into ERROR state and "buries" it in 
> cell0. With a new microversion, the user can attempt to rebuild the 
> server from cell0 and go through scheduling again. This is part of a 
> bigger effort to support pre-emptible instances where scheduling fails 
> during server create, an external reaper service tries to make room by 
> destroying some pre-emptible instances, and then the server gets rebuilt.
> 
> The issue I've found is that if the server was created with personality 
> files using microversion 2.1, fails, and then the user goes to rebuild 
> it, their personality files will be lost because (1) we don't persist 
> personality files anywhere, not even the RequestSpec and (2) 
> microversion 2.57 deprecated the personality files parameter from the 
> rebuild API [2]. Since you'll have to use a newer microversion > 2.57 to 
> rebuild from cell0, you can't specify the personality files again.
> 
> Are we OK with this?

Ummm, yes. Yes, I am completely OK with this.

-jay