apt_updates: textfile metrics of pending apt updates for the node exporter collector

apt_updates/tasks/main.yml

@@ -0,0 +1,41 @@
+# The metrics run after apt-daily (update) and apt-daily-upgrade (upgrade), so they show the state apt
+# just reached without a timer of their own. The "-" lets a failing metrics run leave apt's units green.
+- name: Create the textfile directory
+  ansible.builtin.file:
+    path: "{{ apt_updates_textfile_dir }}"
+    state: directory
+    mode: "0755"
+
+- name: Install the apt metrics script
+  ansible.builtin.template:
+    src: apt-updates-metrics.j2
+    dest: /usr/local/sbin/apt-updates-metrics
+    mode: "0755"
+
+- name: Create the apt timers' drop-in directories
+  ansible.builtin.file:
+    path: /etc/systemd/system/{{ item }}.service.d
+    state: directory
+    mode: "0755"
+  loop:
+    - apt-daily
+    - apt-daily-upgrade
+
+- name: Run the apt metrics after the apt timers' services
+  ansible.builtin.copy:
+    dest: /etc/systemd/system/{{ item }}.service.d/apt-updates-metrics.conf
+    mode: "0644"
+    content: |
+      [Service]
+      ExecStartPost=-/usr/local/sbin/apt-updates-metrics
+  loop:
+    - apt-daily
+    - apt-daily-upgrade
+  register: apt_updates_dropins
+
+- name: Reload systemd after the apt metrics drop-ins
+  ansible.builtin.systemd:
+    daemon_reload: true
+  when: apt_updates_dropins.changed
+  # Check mode does not write the drop-ins.
+  ignore_errors: "{{ ansible_check_mode }}"