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-rabbitmq_server/+/930446
Change-Id: Ia3e4af7986166f0729840d2a61fb8f52ea053676

defaults/main.yml

@@ -232,7 +232,7 @@ keystone_apache_servertokens: "Prod"
 keystone_apache_serversignature: "Off"
 
 ## Apache MPM tunables
-keystone_httpd_mpm_backend: event
+keystone_httpd_mpm_backend: "{{ openstack_apache_mpm_backend | default('event') }}"
 keystone_httpd_mpm_server_limit: "{{ keystone_wsgi_processes }}"
 keystone_httpd_mpm_start_servers: 2
 keystone_httpd_mpm_min_spare_threads: 25

tasks/keystone_apache.yml

@@ -33,6 +33,27 @@
     group: "{{ keystone_apache_default_log_grp }}"
     mode: "0755"
 
+- name: Ensure apache2 MPM for Debian/Ubuntu
+  apache2_module:
+    name: "{{ item.name }}"
+    state: "{{ item.state }}"
+    warn_mpm_absent: false
+  with_items: "{{ keystone_apache_mpms | sort(attribute='state') }}"
+  when:
+    - ansible_facts['pkg_mgr'] == 'apt'
+  notify: Restart web server
+
+- name: Ensure apache2 MPM for EL
+  copy:
+    content: |
+      LoadModule mpm_{{ keystone_httpd_mpm_backend }}_module modules/mod_mpm_{{ keystone_httpd_mpm_backend }}.so
+
+    dest: /etc/httpd/conf.modules.d/00-mpm.conf
+    mode: "0644"
+  when:
+    - ansible_facts['pkg_mgr'] == 'dnf'
+  notify: Restart web server
+
 ## NOTE(cloudnull):
 ## Module enable/disable process is only functional on Debian
 - name: Enable apache2 modules

vars/debian.yml

@@ -82,6 +82,14 @@ keystone_apache_configs:
   - { src: "keystone-httpd.conf.j2", dest: "/etc/apache2/sites-available/keystone-httpd.conf" }
   - { src: "keystone-httpd-mpm.conf.j2", dest: "/etc/apache2/mods-available/mpm_{{ keystone_httpd_mpm_backend }}.conf" }
 
+keystone_apache_mpms:
+  - name: "mpm_event"
+    state: "{{ (keystone_httpd_mpm_backend == 'event') | ternary('present', 'absent') }}"
+  - name: "mpm_worker"
+    state: "{{ (keystone_httpd_mpm_backend == 'worker') | ternary('present', 'absent') }}"
+  - name: "mpm_prefork"
+    state: "{{ (keystone_httpd_mpm_backend == 'prefork') | ternary('present', 'absent') }}"
+
 keystone_apache_modules:
   - name: "ssl"
     state: "{{ (keystone_backend_ssl | bool) | ternary('present', 'absent') }}"