allow to remove non-referenced custom rule files

roles/prometheus/defaults/main.yml

@@ -101,6 +101,8 @@ prometheus_scrape_config_files:
   - prometheus/scrape_configs/*.yml
   - prometheus/scrape_configs/*.json
 
+prometheus_provisioning_synced: false
+
 # yamllint disable rule:line-length
 prometheus_alert_rules:  # noqa yaml[line-length]  # noqa line-length
   - alert: Watchdog

roles/prometheus/meta/argument_specs.yml

@@ -139,6 +139,11 @@ argument_specs:
         default:
           - "prometheus/rules/*.yml"
           - "prometheus/rules/*.yaml"
+      prometheus_provisioning_synced:
+        description:
+          - "Should the provisioning of alert rule files be kept synced. If true, previous provisioned files will be removed if not referenced anymore."
+        type: bool
+        default: false
       prometheus_static_targets_files:
         description:
           - "List of folders where ansible will look for files containing custom static target configuration files which will be copied to C({{ prometheus_config_dir }}/file_sd/)."

roles/prometheus/tasks/configure.yml

@@ -74,6 +74,7 @@
   when:
     - prometheus_alert_rules != []
     - not prometheus_agent_mode
+  register: __rules_managed_copied
   notify:
     - reload prometheus
   become: true
@@ -82,6 +83,16 @@
     - configure
     - prometheus_configure
 
+- name: Register previously copied rules
+  ansible.builtin.find:
+    paths: "{{ prometheus_config_dir }}/rules/"
+  when: prometheus_provisioning_synced
+  register: __rules_present
+  tags:
+    - prometheus
+    - configure
+    - prometheus_configure
+
 - name: Copy custom alerting rule files
   ansible.builtin.copy:
     src: "{{ item }}"
@@ -96,6 +107,30 @@
   notify:
     - reload prometheus
   become: true
+  register: __rules_copied
+  tags:
+    - prometheus
+    - configure
+    - prometheus_configure
+
+- name: Register present and copied rules
+  ansible.builtin.set_fact:
+    __rules_present_list: "{{ __rules_present | json_query('files[*].path') | default([]) }}"
+    __rules_copied_list: "{{ __rules_copied | json_query('results[*].dest') | default([]) }}"
+    __rules_managed_copied_list: "{{ [__rules_managed_copied | json_query('dest')] | default([]) }}"
+  when: prometheus_provisioning_synced
+  tags:
+    - prometheus
+    - configure
+    - prometheus_configure
+
+- name: "Remove rules not present on deployer machine (synchronize)"
+  ansible.builtin.file:
+    path: "{{ item }}"
+    state: absent
+  loop: "{{ __rules_present_list | difference(__rules_copied_list) | difference(__rules_managed_copied_list) }}"
+  become: true
+  when: prometheus_provisioning_synced and not ansible_check_mode
   tags:
     - prometheus
     - configure