[openstack-dev] [nova] [placement] resource providers update 44

Chris Dent cdent+os at anticdent.org
Fri Dec 8 13:57:13 UTC 2017

I'm feeling pressure from the (excellent and welcomed) Weekly Owl


and Keystone update:


to enhance the rp and placement update brand, to maximize market
penetration, global influence, and reader participation, but instead
I'll stick to habit.

# Most Important

The three main themes (nested providers, alternate hosts, migration)
continue to be the main priorities.

A thing to be aware of, now that some of nested has merged on the
placement side, is that the nova side is underway and the work
surrounding the ProviderTree concept is fairly penetrating. It will
supersede the "get_inventory" method in the virt drivers, and thus far
not all the virt drivers have get_inventory methods. See


way down inside the nested-resource-providers topic for a bit of

# What's Changed

Microversion 1.14 has merged (causing a might microversion conflict
pileup behind it) meaning that some aspects of nested providers are in
the placement API. Hierarchies of providers can be created, and trees
of results can be returned:


A fix was merged that defaults the accept header, if not set, to
application/json. This means that whereas in the past an error
response could inadvertently be HTML, it will now be JSON, structured
(partially, critically the 'code' field is not there as we've stumbled
trying to create standards) according to the errors guideline:


Eric made the compute node be more alert when it encounters an error
condition when getting or creating resource providers:


This led to the discovery that in grenade placement was not being
properly stopped and restarted over the upgrade transition:


I mention all this because it's quite likely that latent bugs with
talking to placement (from nova) in grenade will be exposed. Be on
the lookout. If you find something weird, report a bug, and if
possible, fix it.

# Help Wanted

(unchanged from last week, no new data, yet)

A takeaway from summit is that we need, where possible, benchmarking
info from people who are making the transition from old methods of
scheduling to the newer allocation_candidate driven modes.  While
detailed numbers will be most useful, even anecdotal summaries of
"woot it's way better" or "hmmm, no it seems worse" are useful.

# Docs

Quite a few docs improvements have merged. Others need more review:

* https://review.openstack.org/#/c/512215/
    Add create inventories doc for placement

* https://review.openstack.org/#/c/523007/
    Add x-openstack-request-id in API ref

* https://review.openstack.org/#/c/521541/
    Add 'Location' parameters in API ref

* https://review.openstack.org/#/c/511342/
    add API reference for create inventory

# Nested Providers

The nested-resource-providers stack has grown a long tail of changes
for managing nested providers rooted on a compute node:


As mentioned above this has impact for virt drivers.

The current spec for nested providers


doesn't really cover the ProviderTree and inventory management plans
that are currently being implemented in that long tail. That makes it
a bit harder to review than it might otherwise. We may not need a spec
but a sort of explanatory overview may help provide some context on
what needs to happen. A lot of the work that is in progress feels like
it is working to a design where the use cases are not entirely obvious.
There's a danger this can lead to an implementation that is somewhat
divorced for reality. There's no evidence as yet that this is
happening, but there's also none that it's not.

## Alternate Hosts

Having the scheduler request and use alternate hosts:


This has come unstuck and is moving along, but needs continued eyes.

## Migration allocations

Do allocation "doubling" using the migration uuid for the consumer for
one half. This is also very close:


The concept of migration allocations is what drove the work to enable
the POST /allocations handling now at microversion 1.13, so we have
the option to start using that power. Dan helpfully left comments in
the code to indicate where it could be done. Do we want to consider
getting that in before the end of queens, to avoid some racing?

## Misc Traits, Shared, Etc Cleanups

There's a stack of code that's not attached to a blueprint, starting


that fixes up a lot of things related to traits, sharing providers,
test additions and fixes to those tests. At the moment they are a bug


But that is not the only bug they are addressing. Some of the above
probably appear in the list below too.

# Other

This week nothing new is added to the "other" list. I've simply copied
over the previous week's list with anything that's been merged or
abandoned removed. A fair amount has been merged, that's cool.

* https://review.openstack.org/#/c/522002/
    skip authentication on root URI

* https://review.openstack.org/#/c/522407/
    Add aggregates check in allocation canditates

* https://review.openstack.org/#/c/519462/
    Log options at debug when starting API services under wsgi
    (Make any sense to split this into placement and nova versions? One
    seems easier than the other)

* https://review.openstack.org/#/c/506175/
    VMware: implement get_inventory() driver method

* https://review.openstack.org/#/c/508555/
    Re-use existing ComputeNode on ironic rebalance

* https://review.openstack.org/#/q/I0c4ca6a81f213277fe7219cb905a805712f81e36
    Proper error handling by _ensure_resource_provider
    (This is already approved for master, but there are backports.)

* https://review.openstack.org/#/q/topic:bp/placement-osc-plugin
     Build the placement osc plugin

* https://review.openstack.org/#/c/511936/
     Neutron's placement client

* https://review.openstack.org/#/c/521640/
     cache-related headers for placement

* https://review.openstack.org/#/q/topic:bp/request-traits-in-nova
     request traits in nova

* https://review.openstack.org/#/c/513041/
     Extract instance allocation removal code

* https://review.openstack.org/#/c/493865/
     cover migration cases with functional tests

* https://review.openstack.org/#/c/501252/
     doc: note that custom resources are not fully supported

* https://review.openstack.org/#/c/494206/
     Remove the Pike migration code for flavor migration

* https://review.openstack.org/#/c/512497/
     Refactor placement version check

* https://review.openstack.org/#/q/topic:bp/add-support-for-vgpu
     Add support for VGPU

* https://review.openstack.org/#/q/topic:placement_schema_separation
     Put the json schema in their own directory

# End

Your prize this week is one of those sticky octopuses that you throw
at the wall, and it rolls down. Except dressed as Santa Claus.

Chris Dent                      (⊙_⊙')         https://anticdent.org/
freenode: cdent                                         tw: @anticdent

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