enhancement(prometheus): support prometheus2 .yml rule file format

roles/prometheus/defaults/main.yml

@@ -91,7 +91,8 @@ prometheus_scrape_configs:
 prometheus_config_file: 'prometheus.yml.j2'
 
 prometheus_alert_rules_files:
-  - prometheus/rules/*.rules
+  - prometheus/rules/*.yml
+  - prometheus/rules/*.yaml
 
 prometheus_static_targets_files:
   - prometheus/targets/*.yml

roles/prometheus/meta/argument_specs.yml

@@ -129,19 +129,20 @@ argument_specs:
         default: "prometheus.yml.j2"
       prometheus_alert_rules:
         description:
-          - "Full list of alerting rules which will be copied to C({{ prometheus_config_dir }}/rules/ansible_managed.rules)."
-          - "Alerting rules can be also provided by other files located in C({{ prometheus_config_dir }}/rules/) which have C(*.rules) extension"
+          - "Full list of alerting rules which will be copied to C({{ prometheus_config_dir }}/rules/ansible_managed.yml)."
+          - "Alerting rules can be also provided by other files located in C({{ prometheus_config_dir }}/rules/) which have a C(*.yml) or C(*.yaml) extension"
           - "Please see default values in role defaults/main.yml"
         type: "list"
         elements: "dict"
       prometheus_alert_rules_files:
         description:
           - "List of folders where ansible will look for files containing alerting rules which will be copied to C({{ prometheus_config_dir }}/rules/)."
-          - "Files must have C(*.rules) extension"
+          - "Files must have a C(*.yml) or C(*.yaml) extension"
         type: "list"
         elements: "str"
         default:
-          - "prometheus/rules/*.rules"
+          - "prometheus/rules/*.yml"
+          - "prometheus/rules/*.yaml"
       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/molecule/alternative/tests/test_alternative.py

@@ -23,7 +23,7 @@ def test_directories(host, dirs):
 
 @pytest.mark.parametrize("files", [
     "/opt/prom/etc/prometheus.yml",
-    "/opt/prom/etc/rules/ansible_managed.rules",
+    "/opt/prom/etc/rules/ansible_managed.yml",
     "/opt/prom/etc/file_sd/node.yml",
     "/opt/prom/etc/file_sd/docker.yml",
     "/usr/local/bin/prometheus",

roles/prometheus/molecule/default/tests/test_default.py

@@ -46,7 +46,7 @@ def test_files(host, files):
 
 
 @pytest.mark.parametrize("files", [
-    "/etc/prometheus/rules/ansible_managed.rules"
+    "/etc/prometheus/rules/ansible_managed.yml"
 ])
 def test_absent(host, files):
     f = host.file(files)

roles/prometheus/tasks/configure.yml

@@ -1,8 +1,8 @@
 ---
 - name: Alerting rules file
   ansible.builtin.template:
-    src: "alert.rules.j2"
-    dest: "{{ prometheus_config_dir }}/rules/ansible_managed.rules"
+    src: "ansible_managed.yml.j2"
+    dest: "{{ prometheus_config_dir }}/rules/ansible_managed.yml"
     owner: root
     group: "{{ prometheus_system_group }}"
     mode: 0640

roles/prometheus/tasks/preflight.yml

@@ -89,6 +89,17 @@
     - prometheus_alertmanager_config == []
     - prometheus_alert_rules != []
 
+- name: Alert when alert rules files are found in the old .rules format
+  ansible.builtin.debug:
+    msg: >
+      prometheus_alert_rules_files contains rules in the old .rules file format.
+      This format has been deprecated in favour of the new YAML format since Prometheus v2.x.
+      You can update your rules using promtool: promtool update rules <filenames>
+
+      If your rules are already in the YAML format but with the .rules extension, you can safely ignore this message,
+      or rename the files to <filename>.yaml or <filename>.yml to get rid of it.
+  when: prometheus_alert_rules_files | select('search', '.rules$') | list | length > 0
+
 - name: Discover latest version
   ansible.builtin.set_fact:
     prometheus_version: "{{ (lookup('url', 'https://api.github.com/repos/{{ _prometheus_repo}}/releases/latest', headers=_github_api_headers,

roles/prometheus/templates/prometheus.yml.j2

@@ -19,6 +19,8 @@ remote_read:
 
 {% if not prometheus_agent_mode and prometheus_alert_rules_files != [] %}
 rule_files:
+  - {{ prometheus_config_dir }}/rules/*.yml
+  - {{ prometheus_config_dir }}/rules/*.yaml
   - {{ prometheus_config_dir }}/rules/*.rules
 {% endif %}