We currently have three cells v2 documents in-tree:

- A 'user/cellsv2-layout' document that details the structure or
  architecture of a cells v2 deployment (which is to say, any modern
  nova deployment)
- A 'user/cells' document, which is written from a pre-cells v2
  viewpoint and details the changes that cells v2 *will* require and the
  benefits it *would* bring. It also includes steps for upgrading from
  pre-cells v2 (that is, pre-Pike) deployment or a deployment with cells
  v1 (which we removed in Train and probably broke long before)
- An 'admin/cells' document, which doesn't contain much other than some
  advice for handling down cells

Clearly there's a lot of cruft to be cleared out as well as some
centralization of information that's possible. As such, we combine all
of these documents into one document, 'admin/cells'. This is chosen over
'users/cells' since cells are not an end-user-facing feature. References
to cells v1 and details on upgrading from pre-cells v2 deployments are
mostly dropped, as are some duplicated installation/configuration steps.
Formatting is fixed and Sphinx-isms used to cross reference config
option where possible. Finally, redirects are added so that people can
continue to find the relevant resources. The result is (hopefully) a
one stop shop for all things cells v2-related that operators can use to
configure and understand their deployments.

Change-Id: If39db50fd8b109a5a13dec70f8030f3663555065
Signed-off-by: Stephen Finucane <stephenfin@redhat.com>

The 'nova-manage placement audit' tool has functionality that can
delete orphaned allocations in placement. Add a section for it in the
doc for troubleshooting orphaned allocations.

Change-Id: I697de57cf7eb43c0993af2b1f5b3f5c4395ef097

Nested allocations are only partially supported in nova-manage placement
heal_allocations CLI. This patch documents the missing support and
blocks healing instances with VGPU or Cyborg device profile request in
the embedded flavor. Blocking is needed as if --forced is used with such
instances then the tool could recreate an allocation ignoring some of
these resources.

Change-Id: I89ac90d2ea8bc268940869dbbc90352bfad5c0de
Related-Bug: bug/1939020

We had recent bug report about a possible regression related to
affinity policy enforcement with parallel server create requests.

It turned out not to be a regression but because of the complexity
around affinity enforcement, it might help to add a section to the
compute troubleshooting doc about it which we could refer to in the
future.

Related-Bug: #1863190

Change-Id: I508c48183a7205d46e13154d4e92d31dfa7f7d78

Now that the openstack resource provider allocation unset command is
available [1] this change adds a note about using it in the troubleshooting
doc for cleaning up orphaned allocations.

Sub-sections are used to try and separate the two non-heal_allocations
solutions with the recommended solution first (using the new unset command).

While in here I noticed a typo in the heal_allocations section as well and
fixed it.

[1] I627bfd1ff699d075028da6afafbe7fb9b2f13058

Change-Id: I896bb68c4bdd35d051ef3e95e19bdeb472f9bc99
Related-Bug: #1829479

This has come up a few times via support questions from operators
that have a nova cell database out of sync with the placement
database resulting in a mismatch in compute nodes to provider
uuids and they just want to wipe the placement database and rebuild
it from the current data in nova. This provides a document with the
high level steps to do that.

Change-Id: Ie4fed22615f60e132a887fe541771c447fae1082

While we do not have an automated fix for bug 1849479 this provides
a troubleshooting document for working around that issue where
allocations from a server that was evacuated from a down host need
to be cleaned up manually in order to delete the resource provider
and associated compute node/service.

In general this is also a useful guide for linking up the various
resources and terms in nova and how they are reflected in placement
with the relevant commands which is probably something we should
do more of in our docs.

Change-Id: I120e1ddd7946a371888bfc890b5979f2e19288cd
Related-Bug: #1829479