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Placement Update 19-21

And here we have placement update 19-21.

Most Important

The spec for nested magic has been split. The second half contains the parts which should be relatively straightforward. The original retains functionality that may be too complex. An email has been addressed to operators asking for feedback.

Those two specs represent a significant portion of the work planned this cycle. Getting them reviewed and merged is a good thing to do.

What's Changed

  • A few small refactorings plus the removal of null provider protections has improved performance when retrieving 10,000 allocation candidates significantly: from around 36 seconds to 6 seconds.

  • We've chosen to switch to office hours. Ed has started an email thread to determine when they should be.

  • Tetsuro's changes to add a RequestGroupSearchContext have merged. These simplify state management throughout the processing of individual request groups, and help avoid redundant queries.

  • Most of the code for counting (nova) quota usage from placement has merged.

  • Microversion 1.33 of the placement API has merged. This allows more expressive suffixes on granular request groups (e.g., resources_COMPUTE in addition to resources1).


These and other features being considered can be found on the feature worklist.

Some non-placement specs are listed in the Other section below. Note that nova will be having a spec-review-sprint this coming Tuesday. if you're doing that, spending a bit of time on the placement specs would be great too.


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

There are 19 (-1) stories in the placement group. 0 (0) are untagged. 2 (0) are bugs. 4 (-1) are cleanups. 11 (0) are rfes. 2 (0) are docs.

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


osc-placement is currently behind by 12 microversions. No change since the last report. Note: Based on conversations that we see on reviews, explicitly trying to chase microversions when patching the plugin may not be aligned with the point of OSC. We're trying to make a humane interface to getting stuff done with placement. Different microversions allow different takes on stuff. It's the stuff that matters, not the microversion.

Pending Changes:

Main Themes

Nested Magic

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

There is some in progress code, some of it WIPs to expose issues:

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.

Ed Leafe has also been doing some intriguing work on using graph databases with placement. It's not yet clear if or how it could be integrated with mainline placement, but there are likely many things to be learned from the experiment.

Other Placement

Miscellaneous changes can be found in the usual place.

There are several os-traits changes being discussed.

Other Service Users

New discoveries are added to the end. Merged stuff is removed. As announced last week, anything that has had no activity in 4 weeks has been removed (many have been removed).


That's a lot of reviewing. Please help out where you can. Your reward will be brief but sincere moments of joy.

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