Some overcloud nodes are missing in the ansible inventory file generated for migration to ML2OVN

[Roman Safronov]

When trying to perform a migration from ml2ovs to ml2ovn using migration tool, ovn_migration.sh script creates a file hosts_for_migration which includes only single controller and single compute node even on environments with more than 1 compute and controller nodes.

The problem started to happen because output of "/usr/bin/tripleo-ansible-inventory --list" changed after some recent tripleo change.

When running get_role_hosts function from tools/ovn_migration/tripleo_environment/ovn_migration.sh:L143 (get_role_hosts /tmp/ansible-inventory.txt neutron_api) on an environment with 3 controller nodes now we get the following :

jq: error (at /tmp/ansible-inventory.txt:1): Cannot iterate over null (null)
controller-0

in the past the output was correct:
controller-0 controller-1 controller-2

similar for tools/ovn_migration/tripleo_environment/ovn_migration.sh:L158
get_role_hosts /tmp/ansible-inventory.txt neutron_ovs_agent

jq: error (at ansible-inventory_osp16.1_ovs:1): Cannot iterate over null (null)
compute-0 controller-0

while correct output should be:
controller-0 controller-1 controller-2 compute-0 compute-1

Possible solution is to replace L93 in tools/ovn_migration/tripleo_environment/ovn_migration.sh
from
roles=`jq -r \.$role_name\.children\[\] $inventory_file`
to
roles=`roles=`jq -r \.overcloud_$role_name\.children\[\] $inventory_file || jq -r \.$role_name\.children\[\] $inventory_file`

In this case the function returns proper lists of nodes for old and new ansible-inventory file format.

Some details:

output of jq command from tools/ovn_migration/tripleo_environment/ovn_migration.sh:L93
old inventory format
[stack@undercloud-0 ~]$ jq -r \.neutron_api\.children\[\] /tmp/ansible-inventory.txt
Controller

new inventory format
(overcloud) [stack@undercloud-0 ~]$ jq -r \.neutron_api\.children\[\] /tmp/ansible-inventory.txt
overcloud_neutron_api

related snippet from old tripleo-ansible-inventory format:
...
    "neutron_api": {
        "children": [
            "Controller"
        ],
        "vars": {
            "ansible_ssh_user": "heat-admin"
        }
    },
...

related snippet from new tripleo-ansible-inventory format:
...
   "neutron_api": {
        "children": [
            "overcloud_neutron_api"
        ]
    },
    "overcloud_neutron_api": {
        "children": [
            "overcloud_Controller"
        ]
    },

[OpenStack Infra (hudson-openstack)]

Change abandoned by Roman Safronov (<email address hidden>) on branch: master
Review: https://review.opendev.org/737546
Reason: No capacity

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.opendev.org/738192

[OpenStack Infra (hudson-openstack)]

Related fix proposed to branch: master
Review: https://review.opendev.org/738212

[OpenStack Infra (hudson-openstack)]

Change abandoned by Jakub Libosvar (<email address hidden>) on branch: master
Review: https://review.opendev.org/738192
Reason: Abandoned in favor of https://review.opendev.org/#/c/738192

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/738212
Committed: https://git.openstack.org/cgit/openstack/neutron/commit/?id=aa6491a9d91bb5aab6bfaba81cf3a82279a551f7
Submitter: Zuul
Branch: master

commit aa6491a9d91bb5aab6bfaba81cf3a82279a551f7
Author: Oliver Walsh <email address hidden>
Date: Fri Jun 26 15:04:56 2020 +0100

    migration: Use ansible-inventory to parse tripleo inventory

    Instead of adapting to changes to the tripleo inventory structure let
    ansible parse it for us using ansible-inventory.

    Change-Id: I34ad0fd5feed65dd1266993a77f6ebc69fecfdfb
    Closes-bug: #1884764

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: stable/ussuri
Review: https://review.opendev.org/741145

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/741145
Committed: https://git.openstack.org/cgit/openstack/neutron/commit/?id=c0fba2007c53e5120ece6eb6ab84e28a87741d04
Submitter: Zuul
Branch: stable/ussuri

commit c0fba2007c53e5120ece6eb6ab84e28a87741d04
Author: Oliver Walsh <email address hidden>
Date: Fri Jun 26 15:04:56 2020 +0100

    migration: Use ansible-inventory to parse tripleo inventory

    Instead of adapting to changes to the tripleo inventory structure let
    ansible parse it for us using ansible-inventory.

    Change-Id: I34ad0fd5feed65dd1266993a77f6ebc69fecfdfb
    Closes-bug: #1884764
    (cherry picked from commit aa6491a9d91bb5aab6bfaba81cf3a82279a551f7)