r/wal-g-pg: Schedule weekly delete jobs

WAL-G slows down significantly when too many backups are kept.  We need
to periodically clean up old backups to maintain a reasonable level of
performance, and also keep from wasting space with useless old backups.

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

@@ -1,2 +1,7 @@
 wal_g_pg_backup_timer_schedule: >-
   *-*-* 03:56
+
+wal_g_pg_delete_timer_schedule: >-
+  weekly
+wal_g_pg_delete_args: >-
+  retain FIND_FULL 7

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

@@ -6,3 +6,8 @@
   systemd:
     name: wal-g-backup.timer
     state: restarted
+
+- name:  restart wal-g delete timer
+  systemd:
+    name: wal-g-delete.timer
+    state: restarted

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

@@ -1,2 +1,3 @@
 dependencies:
 - dch-yum
+- systemd-base

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

@@ -55,6 +55,30 @@
   tags:
   - systemd
 
+- name: ensure wal-g delete timer is installed
+  template:
+    src: wal-g-delete.timer.j2
+    dest: /etc/systemd/system/wal-g-delete.timer
+    owner: root
+    group: root
+    mode: u=rw,go=r
+  notify:
+  - reload systemd
+  - restart wal-g delete timer
+  tags:
+  - systemd
+- name: ensure wal-g delete service is installed
+  template:
+    src: wal-g-delete.service.j2
+    dest: /etc/systemd/system/wal-g-delete.service
+    owner: root
+    group: root
+    mode: u=rw,go=r
+  notify:
+  - reload systemd
+  tags:
+  - systemd
+
 - name: ensure wal-g backup timer is enabled
   systemd:
     name: wal-g-backup.timer
@@ -62,6 +86,13 @@
   tags:
   - service
 
+- name: ensure wal-g delete timer is enabled
+  systemd:
+    name: wal-g-delete.timer
+    enabled: true
+  tags:
+  - service
+
 - name: flush handlers
   meta: flush_handlers
 
@@ -71,3 +102,10 @@
     state: started
   tags:
   - service
+
+- name: ensure wal-g delete timer is running
+  systemd:
+    name: wal-g-delete.timer
+    state: started
+  tags:
+  - service

roles/wal-g-pg/templates/wal-g-delete.service.j2

@@ -0,0 +1,10 @@
+[Unit]
+Description=PostgreSQL Backup delete 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 delete --config /etc/postgresql/wal-g.yml {{ wal_g_pg_delete_args }} --confirm
+User=postgres

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

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