Ensure that selected Apache MPM is enforced

At the moment services might have different MPM selected while all
operating the same Apache setup, ie on metal setup.
This results in failures to set selected MPMs, so eventually second run
of roles after initial deployment will end up in failure (ie upgrade).

This patch ensures that all except selected MPMs are disabled and do
role get's the desired state of deployment.

We also need to align selected MPM across all roles to avoid
future conflicts.

Depends-On: https://review.opendev.org/c/openstack/openstack-ansible-openstack_hosts/+/930272
Depends-On: https://review.opendev.org/c/openstack/openstack-ansible-repo_server/+/929690
Depends-On: https://review.opendev.org/c/openstack/openstack-ansible-rabbitmq_server/+/930446
Change-Id: I480222993a63af41cfba65464f5b5c8585b2d4fd

defaults/main.yml

@@ -162,6 +162,7 @@ horizon_endpoint_type: internalURL
 
 horizon_server_name: "{{ ansible_facts['fqdn'] | default('horizon') }}"
 
+horizon_apache_mpm_backend: "{{ openstack_apache_mpm_backend | default('event') }}"
 horizon_apache_servertokens: "Prod"
 horizon_apache_serversignature: "Off"
 horizon_log_level: info

releasenotes/notes/horizon_apache_mpm-2a34436635f1bef9.yaml

@@ -0,0 +1,8 @@
+---
+
+upgrade:
+  - |
+    In order to align used Apache MPM across the board, Horizon default
+    MPM is switched from ``worker`` to ``event``.
+    A variable ``horizon_apache_mpm_backend`` was introduced to define
+    the MPM in use.

tasks/horizon_apache.yml

@@ -13,6 +13,28 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+- name: Ensure apache2 MPM for Debian/Ubuntu
+  apache2_module:
+    name: "{{ item.name }}"
+    state: "{{ item.state }}"
+    ignore_configcheck: yes
+    warn_mpm_absent: false
+  with_items: "{{ horizon_apache_mpms | sort(attribute='state') }}"
+  when:
+    - ansible_facts['pkg_mgr'] == 'apt'
+  notify: Restart wsgi process
+
+- name: Ensure apache2 MPM for EL
+  copy:
+    content: |
+      LoadModule mpm_{{ horizon_apache_mpm_backend }}_module modules/mod_mpm_{{ horizon_apache_mpm_backend }}.so
+
+    dest: /etc/httpd/conf.modules.d/00-mpm.conf
+    mode: "0644"
+  when:
+    - ansible_facts['pkg_mgr'] == 'dnf'
+  notify: Restart wsgi process
+
 # NOTE(hwoarang): Module enable/disable process is only functional on Debian
 - name: Enable apache2 modules
   apache2_module:

vars/debian.yml

@@ -53,15 +53,19 @@ horizon_apache_default_sites:
   - "/etc/apache2/sites-enabled/000-default.conf"
   - "/etc/apache2/conf-enabled/other-vhosts-access-log.conf"
 
+horizon_apache_mpms:
+  - name: "mpm_event"
+    state: "{{ (horizon_apache_mpm_backend == 'event') | ternary('present', 'absent') }}"
+  - name: "mpm_worker"
+    state: "{{ (horizon_apache_mpm_backend == 'worker') | ternary('present', 'absent') }}"
+  - name: "mpm_prefork"
+    state: "{{ (horizon_apache_mpm_backend == 'prefork') | ternary('present', 'absent') }}"
+
 horizon_apache_modules:
   - name: "wsgi"
     state: "present"
   - name: "ssl"
     state: "present"
-  - name: "mpm_event"
-    state: "absent"
-  - name: "mpm_worker"
-    state: "present"
   - name: "rewrite"
     state: "present"
   - name: "headers"