Add role to discover Centos latest images

With this patch, we are adding a new role discover-latest-image to
discover the latest Centos Stream image, We are limiting the scope
for C9 for now, We can extend the role for Centos 8 image discovery
in future if there is a need.

Also, we are updating baremetal-prep-virthost.yml playbook to use
this new role for c9 case and in combination with patch[1] - we will
get rid of undercloud baseos hardcoding and use the latest discovered
image.

[1] https://review.opendev.org/c/openstack/tripleo-quickstart/+/838990/

Change-Id: I3a97edc63e96725a1690335f557508d56ed10258

playbooks/baremetal-prep-virthost.yml

@@ -60,6 +60,25 @@
         - ansible_distribution == 'RedHat'
         - ansible_distribution_major_version|int >= 8
 
+- name: Find latest Centos image and set facts for undercloud base image.
+  hosts: virthost
+  gather_facts: true
+  tasks:
+    - block:
+        - name: Discover latest CentOS qcow2 image
+          include_role:
+            name: discover-latest-image
+        - name: set_fact for undercloud base image
+          set_fact:
+            baseos_undercloud_image_url: "{{ discovered_image_url }}"
+            baseos_image: "{{ ansible_distribution | lower }}"
+            baseos_image_type: qcow2
+            baseos_md5sum: "{{ discovered_md5sum }} {{ discovered_image_name }}"
+            cacheable: true
+      when:
+        - ansible_distribution == 'CentOS'
+        - ansible_distribution_major_version is version(9, '>=')
+
 - name: Setup undercloud and baremetal vms and networks in libvirt
   hosts: virthost
   gather_facts: true

roles/discover-latest-image/README.md

@@ -0,0 +1,35 @@
+Role Name
+=========
+
+An Ansible role to discover latest Centos image.
+
+Requirements
+------------
+
+This role is currently written for Centos-9 and can be extended to Centos-8 on need basis.
+
+Role Variables
+--------------
+
+* base_url: <https://cloud.centos.org/centos/{{ ansible_distribution_major_version }}-stream/x86_64/images/> Base Url from where we can pull the Centos Image.
+* qcow_prefix: <CentOS-Stream-GenericCloud-> Qcow2 image prefix on base_url which will be used as a filter to find latest Centos Image.
+
+
+Example Playbook
+----------------
+
+  1. Sample playbook to call the role
+
+    - name: Discover latest CentOS qcow2 image
+      include_role:
+        name: discover-latest-image
+
+  2. Sample config to use the facts from discover-latest-image
+
+    - name: set_fact for undercloud base image
+      set_fact:
+        baseos_undercloud_image_url: "{{ discovered_image_url }}"
+        baseos_image: "{{ ansible_distribution | lower }}"
+        baseos_image_type: qcow2
+        baseos_md5sum: "{{ discovered_md5sum }} {{ discovered_image_name }}"
+        cacheable: true

roles/discover-latest-image/defaults/main.yaml

@@ -0,0 +1,3 @@
+---
+base_url: https://cloud.centos.org/centos/{{ ansible_distribution_major_version }}-stream/x86_64/images/
+qcow_prefix: CentOS-Stream-GenericCloud-

roles/discover-latest-image/tasks/main.yaml

@@ -0,0 +1,45 @@
+---
+- name: Create a temporary file
+  tempfile:
+    state: file
+  register: tempfile
+
+- name: Remove the file at temporary file path.
+  file:
+    path: "{{ tempfile.path }}"
+    state: absent
+
+- name: Fetch publication page
+  get_url:
+    url: "{{ base_url }}?C=M;O=A"
+    dest: "{{ tempfile.path }}"
+
+- name: Find qcow2 url
+  shell: |
+    sed -n "/qcow2/ s/.*\({{ qcow_prefix }}.*.qcow2\)<\/a>.*/\1/p" {{ tempfile.path }} | tail -1
+  register: get_qcow_image_name
+
+- name: Remove the file at temporary file path.
+  file:
+    path: "{{ tempfile.path }}"
+    state: absent
+
+- name: Fetch md5sum file
+  get_url:
+    url: "{{ base_url }}/{{ get_qcow_image_name.stdout }}.MD5SUM"
+    dest: "{{ tempfile.path }}"
+
+- name: Find MD5 value
+  command: "awk -F ' = ' '/MD5/ {print $2}' {{ tempfile.path }}"
+  register: get_md5_value
+
+- name: Remove the file at temporary file path.
+  file:
+    path: "{{ tempfile.path }}"
+    state: absent
+
+- name: "Set expected facts Image: {{ base_url }}{{ get_qcow_image_name.stdout }} Md5sum: {{ get_md5_value.stdout }} "
+  set_fact:
+    discovered_image_name: "{{ get_qcow_image_name.stdout }}"
+    discovered_image_url: "{{ base_url }}{{ get_qcow_image_name.stdout }}"
+    discovered_md5sum: "{{ get_md5_value.stdout }}"