Add Prometheus datasource provisioning for Grafana (#432)

Query all Prometheus servers across domains and provision them as
named datasources (prometheus_<domain>) via Grafana's file-based
provisioning.

Author: SoundGoof

modules/grafana.py

@@ -6,9 +6,18 @@
 
 
 def generate(host, *args):
+    prometheus_servers = {}
+    for server in sorted(lib.get_nodes_with_package('prometheus').keys()):
+        try:
+            domain = lib.get_domain(server).lower()
+        except lib.NoDomainError:
+            domain = 'unknown'
+        prometheus_servers[server] = domain
+
     info = {
     'grafana': {
-        'current_event': lib.get_current_event()
+        'current_event': lib.get_current_event(),
+        'prometheus_servers': prometheus_servers,
         }
     }
 

modules/grafana/manifests/init.pp

@@ -11,7 +11,7 @@
 # for package details such as default paths etc.
 #
 
-class grafana($current_event) {
+class grafana($current_event, $prometheus_servers = []) {
 
   # Adding the apt repository
   package { 'apt-transport-https':
@@ -110,6 +110,15 @@
     }
   }
 
+  # Prometheus datasource provisioning
+  file { 'grafana-prometheus-datasources':
+    path    => '/etc/grafana/provisioning/datasources/prometheus.yaml',
+    content => template('grafana/prometheus-datasource.yaml.erb'),
+    mode    => '0644',
+    require => Package['grafana'],
+    notify  => Service['grafana-server'],
+  }
+
   # Setting up the Apache proxy
   apache::proxy { 'grafana-backend':
     url     => '/',

modules/grafana/templates/prometheus-datasource.yaml.erb

@@ -0,0 +1,12 @@
+# Managed by Puppet - do not edit manually
+apiVersion: 1
+
+datasources:
+<% @prometheus_servers.each do |server, domain| -%>
+  - name: prometheus_<%= domain %>
+    type: prometheus
+    url: http://<%= server %>:9090
+    access: proxy
+    isDefault: false
+    editable: false
+<% end -%>