add promtail support

templates/grafana-promtail.yml.j2

@@ -0,0 +1,37 @@
+server:
+  disable: true
+  http_listen_port: 9080
+  grpc_listen_port: 0
+
+positions:
+  filename: /var/lib/grafana-promtail/positions.yaml
+
+clients:
+{% for i in prometheus_agent.scrapers if prometheus_agent.scrapers[i].get("loki") %}
+{% set lokiconfig = {}|combine({ "external_labels": merged_prometheus_labels|combine( {"instance": inventory_hostname} ) }, prometheus_agent.scrapers[i]['loki'] ) %}
+  - {{ lokiconfig|to_json }}
+{% endfor %}
+
+scrape_configs:
+- job_name: system
+  static_configs:
+  - targets:
+      - localhost
+    labels:
+      job: varlogs
+      __path__: /var/log/*log
+- job_name: journal
+  journal:
+    max_age: 12h
+    labels:
+      job: systemd-journal
+  relabel_configs:
+    - source_labels: ['__journal__systemd_unit']
+      target_label: 'unit'
+- job_name: nginx
+  static_configs:
+  - targets:
+      - localhost
+    labels:
+      job: nginx
+      __path__: /var/log/nginx/access-promtail.log