Merge branch 'postgresql-systemd-improvement' into 'master'

Postgresql systemd improvement

See merge request !1

postgresql/tasks/systemd.yml

 ---
 
-- name: Set PGDATA environment variable on CentOS 7
-  lineinfile:
-    path: /usr/lib/systemd/system/postgresql.service
-    regexp: '^Environment=PGDATA='
-    line: 'Environment=PGDATA={{path_to_icat}}'
-  when: (ansible_facts['distribution'] == "CentOS" and ansible_facts['distribution_major_version'] == "7" and use_distribution_postgresql)
-
-- name: Set PGDATA environment variable on CentOS 7
-  lineinfile:
-    path: /usr/lib/systemd/system/postgresql-{{ external_postgresql_version }}.service
-    regexp: '^Environment=PGDATA='
-    line: 'Environment=PGDATA={{path_to_icat}}'
-  when: (ansible_facts['distribution'] == "CentOS" and ansible_facts['distribution_major_version'] == "7" and not use_distribution_postgresql)
-
-- name: Set PGDATA environment variable on CentOS 8
-  lineinfile:
-    path: /usr/lib/systemd/system/postgresql.service
-    regexp: '^Environment=PGDATA='
-    line: 'Environment=PGDATA={{path_to_icat}}'
-  when: (ansible_facts['distribution'] == "CentOS" and ansible_facts['distribution_major_version'] == "8" and use_distribution_postgresql)
-
-- name: Set PGDATA environment variable on CentOS 8
-  lineinfile:
-    path: /usr/lib/systemd/system/postgresql-{{ external_postgresql_version }}.service
-    regexp: '^Environment=PGDATA='
-    line: 'Environment=PGDATA={{path_to_icat}}'
-  when: (ansible_facts['distribution'] == "CentOS" and ansible_facts['distribution_major_version'] == "8" and not use_distribution_postgresql)
+# Dynamically set some variables commonly used by this task group.
+- name: Setting facts for systemd operations.
+  vars:
+    external_postgres_suffix: "-{{ external_postgresql_version }}" 
+    # Suffix will be '-version', e.g. '-13' for postgresql v13.x.x, or '' (nothing) if we do use the version distributed by the standard repository.
+    suffix: "{{ ( use_distribution_postgresql == false ) | ternary(external_postgres_suffix, '') }}"
+  set_fact:
+    postgres_unit_file_name: "postgresql{{ suffix }}.service"
+
+# This task will place an 'override' for the systemd unit file distributed by postgresql.
+# Modifying the original unit file is not recomended as it is replaced with each update of postgresql.
+#
+# Its current purpose is to define the path to the data directory where the database's actual data will be on the system.
+# cf. The template file.
+- name: "Define the {{ postgres_unit_file_name }} override file."
+  template:
+    src: templates/postgresql.service.j2
+    dest: "/etc/systemd/system/{{ postgres_unit_file_name }}"
+    owner: root
+    group: wheel
+    mode: '0644'
+  when:
+    - path_to_icat is defined
+    - path_to_icat != None
+    - path_to_icat | length > 0
 
 - name: Start postgresql service on CentOS 7
   systemd:
@@ -36,7 +34,7 @@
     enabled: yes
   when: (ansible_facts['distribution'] == "CentOS" and ansible_facts['distribution_major_version'] == "7" and use_distribution_postgresql)
 
-- name: Start postgresql-{{ postgresql_version }} service on CentOS 7
+- name: Start postgresql-{{ external_postgresql_version }} service on CentOS 7
   systemd: 
     name: postgresql-{{ external_postgresql_version }}
     state: started

postgresql/templates/postgresql.service.j2

+.include /usr/lib/systemd/system/{{ postgres_unit_file_name }}
+
+[Service]
+Environment=PGDATA={{ path_to_icat }}
+