Move nova-cells-v1 to experimental queue

Cells v1 has been deprecated since Pike. CERN
has been running with cells v2 since Queens.
The cells v1 job used to be the only thing that
ran with nova-network, but we switched the job
to use neutron in Rocky:

  I9de6b710baffdffcd1d7ab19897d5776ef27ae7e

The cells v1 job also suffers from intermittent
test failures, like with snapshot tests.

Given the deprecated nature of cells v1 we should
just move it to the experimental queue so that it
can be run on-demand if desired but does not gate
on all nova changes, thus further moving along its
eventual removal.

This change also updates the cells v1 status doc
and adds some documentation about the different
job queues that nova uses for integration testing.

Change-Id: I74985f1946fffd0ae4d38604696d0d4656b6bf4e
Closes-Bug: #1807407

.zuul.yaml

@@ -205,7 +205,6 @@
               # code; we don't need to run this on all changes, nor do we run
               # it in the gate.
               - ^(?!nova/network/.*)(?!nova/virt/libvirt/vif.py).*$
-        - nova-cells-v1
         - nova-live-migration
         - nova-lvm
         - nova-multiattach
@@ -225,7 +224,6 @@
       jobs:
         - neutron-grenade:
             irrelevant-files: *dsvm-irrelevant-files
-        - nova-cells-v1
         - nova-live-migration
         - nova-multiattach
         - nova-tox-functional
@@ -255,6 +253,7 @@
             irrelevant-files: *dsvm-irrelevant-files
         - tempest-pg-full:
             irrelevant-files: *dsvm-irrelevant-files
+        - nova-cells-v1
         - nova-tempest-full-oslo.versionedobjects:
             irrelevant-files: *dsvm-irrelevant-files
         - legacy-tempest-dsvm-nova-libvirt-kvm-apr:

doc/source/contributor/testing.rst

@@ -85,7 +85,16 @@ Integration tests
 -----------------
 
 Today, our integration tests involve running the Tempest test suite on a
-variety of Nova deployment scenarios.
+variety of Nova deployment scenarios. The integration job setup is defined
+in the ``.zuul.yaml`` file in the root of the nova repository. Jobs are
+restricted by queue:
+
+* ``check``: jobs in this queue automatically run on all proposed changes even
+  with non-voting jobs
+* ``gate``: jobs in this queue automatically run on all approved changes
+  (voting jobs only)
+* ``experimental``: jobs in this queue are non-voting and run on-demand by
+  leaving a review comment on the change of "check experimental"
 
 In addition, we have third parties running the tests on their preferred Nova
 deployment scenario.

doc/source/user/cells.rst

@@ -57,6 +57,12 @@ Because of this, there are a few restrictions placed on cells v1:
    tests are added to Tempest which trigger a latent bug in cells v1 it may not
    be fixed. However, regressions in working function should be tracked with
    bugs and fixed.
+#. Changes proposed to nova will not be automatically tested against a Cells v1
+   environment. To manually trigger Cells v1 integration testing on a nova
+   change in Gerrit, leave a review comment of "check experimental" and the
+   *nova-cells-v1* job will run on it, but the job is non-voting, meaning if
+   it fails it will not prevent the patch from being merged if approved by the
+   core team.
 
 **Suffice it to say, new deployments of cells v1 are not encouraged.**
 

releasenotes/notes/stein-nova-cells-v1-experimental-ci-de47b3c62e5fb675.yaml

@@ -0,0 +1,9 @@
+---
+other:
+  - |
+    CI testing of Cells v1 has been moved to the ``experimental`` queue meaning
+    changes proposed to nova will not be tested against a Cells v1 setup unless
+    explicitly run through the ``experimental`` queue by leaving a review
+    comment on the patch of "check experimental". Cells v1 has been deprecated
+    since the 16.0.0 Pike release and this is a further step in its eventual
+    removal.