Automatically add Prometheus as a Grafana datasource

Assuming both Prometheus and Grafana are enabled, this change
configures Grafana such that it can use data collected by the
Prometheus server.

Partially-Implements: blueprint prometheus
Change-Id: I0290806d0c622b1de33cf7047f099795b4c780b9

ansible/roles/grafana/handlers/main.yml

@@ -20,3 +20,4 @@
       or grafana_conf.changed | bool
       or grafana_container.changed | bool
       or grafana_home_dashboard.changed | bool
+      or grafana_prometheus_data_source.changed | bool

ansible/roles/grafana/tasks/config.yml

@@ -80,6 +80,26 @@
   notify:
     - Restart grafana container
 
+- name: Configuring Prometheus as data source for Grafana
+  vars:
+    service: "{{ grafana_services['grafana'] }}"
+  template:
+    src: "{{ item }}"
+    dest: "{{ node_config_directory }}/grafana/prometheus.yaml"
+    mode: "0660"
+  become: true
+  register: grafana_prometheus_data_source
+  when:
+    - inventory_hostname in groups[service.group]
+    - service.enabled | bool
+    - enable_prometheus | bool
+  with_first_found:
+    - "{{ node_custom_config }}/grafana/{{ inventory_hostname }}/prometheus.yaml"
+    - "{{ node_custom_config }}/grafana/prometheus.yaml"
+    - "prometheus.yaml.j2"
+  notify:
+    - Restart grafana container
+
 - name: Check grafana containers
   kolla_docker:
     action: "compare_container"

ansible/roles/grafana/templates/grafana.ini.j2

@@ -2,6 +2,7 @@
 data = /var/lib/grafana
 logs = /var/log/kolla/grafana
 plugins = /var/lib/grafana/plugins
+provisioning = /etc/grafana/provisioning
 
 [server]
 protocol = http

ansible/roles/grafana/templates/grafana.json.j2

@@ -21,6 +21,13 @@
             "owner": "root",
             "perm": "0644",
             "optional": true
+        },
+        {
+            "source": "{{ container_config_directory }}/prometheus.yaml",
+            "dest": "/etc/grafana/provisioning/datasources/prometheus.yaml",
+            "owner": "root",
+            "perm": "0644",
+            "optional": true
         }
     ],
     "permissions": [

ansible/roles/grafana/templates/prometheus.yaml.j2

@@ -0,0 +1,9 @@
+apiVersion: 1
+
+datasources:
+- name: Prometheus
+  type: prometheus
+  access: proxy
+  orgId: 1
+  url: http://{{ kolla_internal_vip_address }}:{{ prometheus_port }}
+  version: 1