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Placement Update 19-24

Here's a 19-24 pupdate. Last week I said there wouldn't be one this week. I was wrong. There won't be one next week. I'm taking the week off to reset (I hope). I've tried to make sure that there's nothing floating about in Placement land that is blocking on me.

Most Important

The spec for nested magic is close. What it needs now is review from people outside the regulars to make sure it doesn't suffer from tunnel vision. The features discussed form the foundation for Placement being able to service queries for real world uses of nested providers. Placement can already model nested providers but asking for the right one has needed some work.


I read an article this morning which touches on the importance of considering cognitive load in software design. It's fully of glittering generalities, but it reminds me of some of the reasons why it was important to keep a solid boundary between Nova and Placement and why, now that Placement is extracted, the complexity of this nested magic is something we need to measure against the cognitive load it will induce in the people who come after us as developers and users.

What's Changed

  • Support for mappings in allocation candidates has merged as microversion 1.34.

  • Gibi made it so OSProfiler works with placement again.


Some non-placement specs are listed in the Other section below.


(Numbers in () are the change since the last pupdate.)

There are 23 (3) stories in the placement group. 0 (0) are untagged. 4 (1) are bugs. 5 (-1) are cleanups. 11 (0) are rfes. 3 (1) are docs.

If you're interested in helping out with placement, those stories are good places to look.

1832814: Placement API appears to have issues when compute host replaced is an interesting bug. In a switch from RDO to OSA, resource providers are being duplicated because of a change in node name.


osc-placement is currently behind by 11 microversions.

Main Themes

Nested Magic

The overview of the features encapsulated by the term "nested magic" are in a story and spec.

Code related to this:

Consumer Types

Adding a type to consumers will allow them to be grouped for various purposes, including quota accounting. A spec has started. There are some questions about request and response details that need to be resolved, but the overall concept is sound.


We continue to do cleanup work to lay in reasonable foundations for the nested work above. As a nice bonus, we keep eking out additional performance gains too.

Other Placement

Miscellaneous changes can be found in the usual place.

There are five os-traits changes being discussed. And one os-resource-classes change.

Other Service Users

New discoveries are added to the end. Merged stuff is removed. Anything that has had no activity in 4 weeks has been removed.


Go outside. Reflect a bit. Then do.

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