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Placement Update 19-30

Pupdate 19-30 is brought to you by the letter P for Performance.

Most Important

The main things on the Placement radar are implementing Consumer Types and cleanups, performance analysis, and documentation related to nested resource providers.

What's Changed


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

There are 23 (2) stories in the placement group. 0 (0) are untagged. 3 (1) are bugs. 5 (0) are cleanups. 11 (1) are rfes. 4 (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.

  • Add support for multiple member_of. There's been some useful discussion about how to achieve this, and a consensus has emerged on how to get the best results.

  • Adds a new '--amend' option which can update resource provider inventory without requiring the user to pass a full replacement for inventory

Main Themes

Consumer Types

Adding a type to consumers will allow them to be grouped for various purposes, including quota accounting.


Cleanup is an overarching theme related to improving documentation, performance and the maintainability of the code. The changes we are making this cycle are fairly complex to use and are fairly complex to write, so it is good that we're going to have plenty of time to clean and clarify all these things.

I started some performance analysis this week. Initially I started working with placement master in a container but as I started making changes I moved back to container-less. What I discovered was that there is quite a bit of redundancy in the code in the objects package that I was able to remove. For example we were creating at least twice as many ProviderSummary objects than required in a situation with multiple request groups. It's likely there would have been more duplicates with more request groups. That's improved in this change, which is at the end of a stack of several other like-minded improvements.

The improvements in that stack will not be obvious until the more complex nested topology is generally available. My analysis was based on that topology.

Not to put too fine a point on it, but this kind of incremental analysis and improvement is something I think we (the we that is the community of OpenStack) should be doing far more often. It is incredibly revealing about how the system works and opportunities for making the code both work better and be easier to maintain.

One outcome of this work will be something like a Deployment Considerations document to help people choose how to tweak their placement deployment to match their needs. The simple answer is use more web servers and more database servers, but that's often very wasteful.

Other Placement

Miscellaneous changes can be found in the usual place.

There is one os-traits changes being discussed. And two os-resource-classes changes.

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.


I started working with around approximately 20,000 providers this week. Only 980,000 to go.

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