add prometheus role

roles/prometheus/molecule/default/prometheus/prometheus.yml

@@ -0,0 +1,14 @@
+---
+global:
+  scrape_interval:     15s
+  evaluation_interval: 15s
+
+rule_files:
+  - /etc/prometheus/conf/alertules.yml
+  # - "first.rules"
+  # - "second.rules"
+
+scrape_configs:
+  - job_name: prometheus
+    static_configs:
+      - targets: ['localhost:9090']

roles/prometheus/molecule/default/prometheus/rules/alertrules.yml

@@ -0,0 +1,13 @@
+groups:
+- name: example
+  labels:
+    team: myteam
+  rules:
+  - alert: HighRequestLatency
+    expr: job:request_latency_seconds:mean5m{job="myjob"} > 0.5
+    for: 10m
+    keep_firing_for: 5m
+    labels:
+      severity: page
+    annotations:
+      summary: High request latency