[prometheus] Allow custom alert rules to be configured.

This patch extends the configuration task for prometheus
to allow the operator to pass a(set) of prometheus alert
rules files, that will be used by alertmanager to produce
alerts.

This functionality is only enabled when the prometheus-alertmanager
service is enabled.

Change-Id: I882759c3774f43640631c1058f8a9cb24e7a60d2
Closes-Bug: #1776529
Signed-off-by: Jorge Niedbalski <jorge.niedbalski@linaro.org>

ansible/roles/prometheus/handlers/main.yml

@@ -138,4 +138,5 @@
     - inventory_hostname in groups[service.group]
     - service.enabled | bool
     - config_json.changed | bool
+      or prometheus_alertmanager_confs.changed | bool
       or prometheus_container.changed | bool

ansible/roles/prometheus/tasks/config.yml

@@ -24,6 +24,32 @@
   notify:
     - Restart {{ item.key }} container
 
+- name: Find custom prometheus alert rules files
+  local_action:
+    module: find
+    path: "{{ node_custom_config }}/prometheus/"
+    pattern: "*.rules"
+  run_once: True
+  register: prometheus_alert_rules
+  when:
+    - enable_prometheus_alertmanager | bool
+
+- name: Copying over custom prometheus alert rules files
+  vars:
+    service: "{{ prometheus_services['prometheus-server']}}"
+  copy:
+    src: "{{ item.path }}"
+    dest: "{{ node_config_directory }}/prometheus-server/{{ item.path | basename }}"
+    mode: "0660"
+  register: prometheus_confs
+  when:
+    - inventory_hostname in groups[service.group]
+    - service.enabled | bool and enable_prometheus_alertmanager | bool
+    - prometheus_alert_rules is defined and prometheus_alert_rules.files | length > 0
+  with_items: "{{ prometheus_alert_rules.files }}"
+  notify:
+    - Restart prometheus-server container
+
 - name: Copying over prometheus config file
   vars:
     service: "{{ prometheus_services['prometheus-server']}}"
@@ -44,16 +70,17 @@
 - name: Copying over prometheus alertmanager config file
   vars:
     service: "{{ prometheus_services['prometheus-alertmanager']}}"
-  merge_yaml:
-    sources:
-      - "{{ node_custom_config }}/prometheus/{{ inventory_hostname }}/prometheus-alertmanager.yml"
-      - "{{ node_custom_config }}/prometheus/prometheus-alertmanager.yml"
-      - "{{ role_path }}/templates/prometheus-alertmanager.yml.j2"
+  template:
+    src: "{{ item }}"
     dest: "{{ node_config_directory }}/prometheus-alertmanager/prometheus-alertmanager.yml"
-  register: prometheus_confs
+  register: prometheus_alertmanager_confs
   when:
     - inventory_hostname in groups[service.group]
     - service.enabled | bool
+  with_first_found:
+    - "{{ node_custom_config }}/prometheus/{{ inventory_hostname }}/prometheus-alertmanager.yml"
+    - "{{ node_custom_config }}/prometheus/prometheus-alertmanager.yml"
+    - "{{ role_path }}/templates/prometheus-alertmanager.yml.j2"
   notify:
     - Restart prometheus-alertmanager container
 
@@ -81,6 +108,7 @@
     name: "{{ item.value.container_name }}"
     image: "{{ item.value.image }}"
     volumes: "{{ item.value.volumes }}"
+    dimensions: "{{ item.value.dimensions }}"
   register: check_prometheus_containers
   when:
     - kolla_action != "config"

ansible/roles/prometheus/templates/prometheus-server.json.j2

@@ -7,6 +7,15 @@
             "owner": "prometheus",
             "perm": "0600"
         }
+{% if enable_prometheus_alertmanager %}
+        ,{
+            "source": "{{ container_config_directory }}/*.rules",
+            "dest": "/etc/prometheus/",
+            "optional": true,
+            "owner": "prometheus",
+            "perm": "0600"
+        }
+{% endif %}
     ],
     "permissions": [
         {

ansible/roles/prometheus/templates/prometheus.yml.j2

@@ -5,6 +5,13 @@ global:
   external_labels:
     monitor: 'kolla'
 
+{% if prometheus_alert_rules is defined and prometheus_alert_rules.files | length  > 0 %}
+rule_files:
+{% for rule in prometheus_alert_rules.files %}
+  - "/etc/prometheus/{{ rule.path | basename }}"
+{% endfor %}
+{% endif %}
+
 scrape_configs:
   - job_name: prometheus
     static_configs: