[openstack-dev] [nova][placement] Trying to summarize bp/glance-image-traits scheduling alternatives for rebuild

Eric Fried openstack at fried.cc
Thu May 3 21:40:05 UTC 2018

>> verify with placement
>> whether the image traits requested are 1) supported by the compute
>> host the instance is residing on and 2) coincide with the
>> already-existing allocations.

Note that #2 is a subset of #1.  The only potential advantage of
including #1 is efficiency: We can do #1 in one API call and bail early
if it fails; but if it passes, we have to do #2 anyway, which is
multiple steps.  So would we rather save one step in the "good path" or
potentially N-1 steps in the failure case?  IMO the cost of the
additional dev/test to implement #1 is higher than that of the potential
extra API calls.  (TL;DR: just implement #2.)


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