feat(monitoring): add grafana, prometheus, node_exporter roles

- grafana: postgres backend, provisioning (prometheus datasource + node/NUT dashboards)
- prometheus: native service, scrape config via host_vars, localhost bind
- node_exporter: host metrics exporter (localhost:9100)

roles/prometheus/templates/nginx-vhost.conf.j2

@@ -0,0 +1,30 @@
+server {
+    listen 80;
+    listen [::]:80;
+    server_name {{ prometheus_nginx_server_name }};
+    return 301 https://$server_name$request_uri;
+}
+
+server {
+    listen 443 ssl http2;
+    listen [::]:443 ssl http2;
+    server_name {{ prometheus_nginx_server_name }};
+
+    ssl_certificate {{ prometheus_nginx_ssl_certificate }};
+    ssl_certificate_key {{ prometheus_nginx_ssl_certificate_key }};
+
+    ssl_protocols TLSv1.2 TLSv1.3;
+    ssl_ciphers HIGH:!aNULL:!MD5;
+    ssl_prefer_server_ciphers on;
+
+    access_log /var/log/nginx/prometheus_access.log;
+    error_log /var/log/nginx/prometheus_error.log;
+
+    location / {
+        proxy_pass http://{{ prometheus_web_listen_address }};
+        proxy_set_header Host $host;
+        proxy_set_header X-Real-IP $remote_addr;
+        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
+        proxy_set_header X-Forwarded-Proto $scheme;
+    }
+}

roles/prometheus/templates/prometheus-env.conf.j2

@@ -0,0 +1,2 @@
+# Managed by Ansible - DO NOT EDIT MANUALLY
+{{ prometheus_args_var }}="--web.listen-address={{ prometheus_web_listen_address }}"

roles/prometheus/templates/prometheus.yml.j2

@@ -0,0 +1,60 @@
+# Prometheus configuration file
+# Managed by Ansible - DO NOT EDIT MANUALLY
+
+global:
+  scrape_interval: {{ prometheus_scrape_interval }}
+  evaluation_interval: {{ prometheus_evaluation_interval }}
+{% if prometheus_web_external_url %}
+  external_labels:
+    monitor: '{{ prometheus_web_external_url }}'
+{% endif %}
+
+{% if prometheus_alertmanager_configs | length > 0 %}
+alerting:
+  alertmanagers:
+{% for alertmanager in prometheus_alertmanager_configs %}
+    - {{ alertmanager | to_nice_yaml(indent=2) | indent(6) }}
+{% endfor %}
+{% endif %}
+
+{% if prometheus_rule_files | length > 0 %}
+rule_files:
+{% for rule_file in prometheus_rule_files %}
+  - {{ rule_file }}
+{% endfor %}
+{% endif %}
+
+scrape_configs:
+{% for scrape_config in prometheus_scrape_configs %}
+  - job_name: '{{ scrape_config.job_name }}'
+{% if scrape_config.scrape_interval is defined %}
+    scrape_interval: {{ scrape_config.scrape_interval }}
+{% endif %}
+{% if scrape_config.scrape_timeout is defined %}
+    scrape_timeout: {{ scrape_config.scrape_timeout }}
+{% endif %}
+{% if scrape_config.metrics_path is defined %}
+    metrics_path: {{ scrape_config.metrics_path }}
+{% endif %}
+{% if scrape_config.static_configs is defined %}
+    static_configs:
+{% for static_config in scrape_config.static_configs %}
+      - targets:
+{% for target in static_config.targets %}
+          - {{ target }}
+{% endfor %}
+{% if static_config.labels is defined %}
+        labels:
+{% for label_key, label_value in static_config.labels.items() %}
+          {{ label_key }}: {{ label_value }}
+{% endfor %}
+{% endif %}
+{% endfor %}
+{% endif %}
+{% if scrape_config.relabel_configs is defined %}
+    relabel_configs:
+{% for relabel_config in scrape_config.relabel_configs %}
+      - {{ relabel_config | to_nice_yaml(indent=2) | indent(8) }}
+{% endfor %}
+{% endif %}
+{% endfor %}