On 05/02/2018 10:07 AM, Matt Riedemann wrote:
On 5/1/2018 5:26 PM, Arvind N wrote:
In cases of rebuilding of an instance using a different image where
the image traits have changed between the original launch and the
rebuild, is it reasonable to ask to just re-launch a new instance with
the new image?
The argument for this approach is that given that the requirements
have changed, we want the scheduler to pick and allocate the
appropriate host for the instance.
We don't know if the requirements have changed with the new image until
we check them.
Here is another option:
What if the API compares the original image required traits against the
new image required traits, and if the new image has required traits
which weren't in the original image, then (punt) fail in the API? Then
you would at least have a chance to rebuild with a new image that has
required traits as long as those required traits are less than or equal
to the originally validated traits for the host on which the instance is
currently running.
That's pretty much what I had suggested earlier, yeah.
Option 10: Don't support image-defined traits at all. I know that won't
happen though.
At this point I'm exhausted with this entire issue and conversation and
will probably bow out and need someone else to step in with different
perspective, like melwitt or dansmith.
All of the solutions are bad in their own way, either because they add
technical debt and poor user experience, or because they make rebuild
more complicated and harder to maintain for the developers.
I hear your frustration. And I agree all of the solutions are bad in
their own way.
My personal preference is to add less technical debt and go with a
solution that checks if image traits have changed in nova-api and if so,
simply refuse to perform a rebuild.
Best,
-jay
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