r/wal-g-pg: Schedule daily backups

WAL archives are not much good without a base backup onto which they
can be applied.  Thus, we need to schedule WAL-G to create and upload a
backup periodically.

roles/wal-g-pg/defaults/main.yml

@@ -0,0 +1,2 @@
+wal_g_pg_backup_timer_schedule: >-
+  *-*-* 03:56

roles/wal-g-pg/files/wal-g-backup.service

@@ -0,0 +1,9 @@
+[Unit]
+Description=PostgreSQL Backup with WAL-G
+Wants=network-online.target
+After=network-online.target
+
+[Service]
+Type=oneshot
+Environment=PGDATA=/var/lib/pgsql/data
+ExecStart=/usr/bin/wal-g-pg backup-push --config /etc/postgresql/wal-g.yml $PGDATA

roles/wal-g-pg/handlers/main.yml

@@ -1,3 +1,8 @@
 - name: load wal-g-postgresql selinux module
   command:
     semodule -i /usr/local/share/selinux/wal-g-postgresql.cil
+
+- name:  restart wal-g backup timer
+  systemd:
+    name: wal-g-backup.timer
+    state: restarted

roles/wal-g-pg/tasks/main.yml

@@ -34,5 +34,40 @@
   tags:
   - selinux
 
+- name: ensure wal-g backup timer is installed
+  template:
+    src: wal-g-backup.timer.j2
+    dest: /etc/systemd/system/wal-g-backup.timer
+    owner: root
+    group: root
+    mode: u=rw,go=r
+  notify:
+  - restart wal-g backup timer
+  tags:
+  - systemd
+- name: ensure wal-g backup service is installed
+  copy:
+    src: wal-g-backup.service
+    dest: /etc/systemd/system/wal-g-backup.service
+    owner: root
+    group: root
+    mode: u=rw,go=r
+  tags:
+  - systemd
+
+- name: ensure wal-g backup timer is enabled
+  systemd:
+    name: wal-g-backup.timer
+    enabled: true
+  tags:
+  - service
+
 - name: flush handlers
   meta: flush_handlers
+
+- name: ensure wal-g backup timer is running
+  systemd:
+    name: wal-g-backup.timer
+    state: started
+  tags:
+  - service

roles/wal-g-pg/templates/wal-g-backup.timer.j2

@@ -0,0 +1,9 @@
+[Unit]
+Description=Daily PostgreSQL backup with WAL-G
+
+[Timer]
+OnCalendar={{ wal_g_pg_backup_timer_schedule }}
+Persistent=yes
+
+[Install]
+WantedBy=timers.target