Refactor ceph-mgr package installation

The code for installing the ceph-mgr packages had several conditionals
which mean that certain features are only available on specific
operating systems and any OS specific packaging differences must be expressed
entirely in ansible tasks.

This patch takes a design pattern used extensively in openstack-ansible
and uses it for the ceph-mgr installation. The packages to install are
specificed in OS specific vars files which are loaded as required at
runtime and referenced through the role defaults.

This means that the OS specific conditionals are removed from the
ansible tasks, and the deployer can now override the package lists
supplied in the ceph-mgr vars if required.

This patch fixes two install failures, Centos-8 does not have python3-saml [1]
so this package is commented out as it is not generally available, and
all debian derivative OS are assumed to be running python3, so python3-routes
is preferred instead of python-routes which fixes installs on Ubuntu Focal.

[1] https://bugzilla.redhat.com/show_bug.cgi?id=1819302

roles/ceph-mgr/defaults/main.yml

@@ -21,9 +21,9 @@ ceph_mgr_modules: []
 # PACKAGES #
 ############
 # Ceph mgr packages to install, ceph-mgr + extra module packages.
-ceph_mgr_packages:
-  - ceph-mgr
-
+ceph_mgr_packages: "{{ _ceph_mgr_packages }}"
+ceph_mgr_dashboard_packages: "{{ _ceph_mgr_dashboard_packages }}"
+ceph_mgr_all_packages: "{{ ceph_mgr_packages + ((dashboard_enabled | bool) | ternary(ceph_mgr_dashboard_packages, [])) }}"
 
 ##########
 # DOCKER #

roles/ceph-mgr/tasks/main.yml

@@ -1,4 +1,16 @@
 ---
+- name: Gather variables for each operating system
+  include_vars: "{{ item }}"
+  with_first_found:
+    - "{{ ansible_distribution | lower }}-{{ ansible_distribution_version | lower }}.yml"
+    - "{{ ansible_distribution | lower }}-{{ ansible_distribution_major_version | lower }}.yml"
+    - "{{ ansible_os_family | lower }}-{{ ansible_distribution_major_version | lower }}.yml"
+    - "{{ ansible_distribution | lower }}.yml"
+    - "{{ ansible_os_family | lower }}-{{ ansible_distribution_version.split('.')[0] }}.yml"
+    - "{{ ansible_os_family | lower }}.yml"
+  tags:
+    - always
+
 - name: set_fact container_exec_cmd
   set_fact:
     container_exec_cmd: "{{ container_binary }} exec ceph-mon-{{ hostvars[item]['ansible_hostname'] }}"

roles/ceph-mgr/tasks/pre_requisite.yml

@@ -1,45 +1,17 @@
 ---
-- name: set_fact ceph_mgr_packages for sso
-  set_fact:
-    ceph_mgr_packages: "{{ ceph_mgr_packages | union(['python3-saml' if ansible_distribution_major_version | int == 8 else 'python-saml']) }}"
-  when:
-    - dashboard_enabled | bool
-    - ansible_distribution == 'RedHat'
-
-- name: set_fact ceph_mgr_packages for dashboard
-  set_fact:
-    ceph_mgr_packages: "{{ ceph_mgr_packages | union(['ceph-mgr-dashboard']) }}"
-  when: dashboard_enabled | bool
-
-- name: set_fact ceph_mgr_packages for non el7 distribution
-  set_fact:
-    ceph_mgr_packages: "{{ ceph_mgr_packages | union(['ceph-mgr-diskprediction-local']) }}"
-  when:
-    - ansible_os_family != 'RedHat'
-    - ansible_distribution_major_version | int != 7
-
 - name: install ceph-mgr packages on RedHat or SUSE
   package:
-    name: '{{ ceph_mgr_packages }}'
+    name: '{{ ceph_mgr_all_packages }}'
     state: "{{ (upgrade_ceph_packages|bool) | ternary('latest','present') }}"
   register: result
   until: result is succeeded
   when: ansible_os_family in ['RedHat', 'Suse']
 
 - name: install ceph-mgr packages for debian
   apt:
-    name: '{{ ceph_mgr_packages }}'
+    name: '{{ ceph_mgr_all_packages }}'
     state: "{{ (upgrade_ceph_packages|bool) | ternary('latest','present') }}"
     default_release: "{{ ceph_stable_release_uca | default('') if ceph_origin == 'repository' and ceph_repository == 'uca' else ''}}{{ ansible_distribution_release ~ '-backports' if ceph_origin == 'distro' and ceph_use_distro_backports else '' }}"
   register: result
   until: result is succeeded
   when: ansible_os_family == 'Debian'
-
-- name: install routes python library for dashboard module
-  apt:
-    name: python-routes
-  register: result
-  until: result is succeeded
-  when:
-    - ansible_os_family == 'Debian'
-    - "'ceph-mgr-dashboard' in ceph_mgr_packages"

roles/ceph-mgr/vars/debian.yml

@@ -0,0 +1,8 @@
+---
+_ceph_mgr_packages:
+  - ceph_mgr
+  - ceph-mgr-diskprediction-local
+
+_ceph_mgr_dashboard_packages:
+  - ceph_mgr_dashboard
+  - python3-routes

roles/ceph-mgr/vars/redhat-7.yml

@@ -0,0 +1,8 @@
+---
+_ceph_mgr_packages:
+  - ceph_mgr
+
+_ceph_mgr_dashboard_packages:
+  - ceph_mgr_dashboard
+  # python-saml does not appear to be available outside of RHEL subscriptions
+  # - python-saml

roles/ceph-mgr/vars/redhat-8.yml

@@ -0,0 +1,9 @@
+---
+_ceph_mgr_packages:
+  - ceph_mgr
+  - ceph_mgr_diskprediction-local
+
+_ceph_mgr_dashboard_packages:
+  - ceph_mgr_dashboard
+  # python3-saml does not appear to be available outside of RHEL subscriptions
+  # - python3-saml