[openstack-dev] [placement] The "intended purpose" of traits

Eric Fried openstack at fried.cc
Fri Sep 28 13:25:21 UTC 2018

It's time somebody said this.

Every time we turn a corner or look under a rug, we find another use
case for provider traits in placement. But every time we have to have
the argument about whether that use case satisfies the original
"intended purpose" of traits.

That's only reason I've ever been able to glean: that it (whatever "it"
is) wasn't what the architects had in mind when they came up with the
idea of traits. We're not even talking about anything that would require
changes to the placement API. Just, "Oh, that's not a *capability* -
shut it down."

Bubble wrap was originally intended as a textured wallpaper and a
greenhouse insulator. Can we accept the fact that traits have (many,
many) uses beyond marking capabilities, and quit with the arbitrary

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