prometheus: add retention setting

roles/prometheus/tasks/main.yml

@@ -1,9 +1,5 @@
 ---
 
-- name: Check OS release
-  fail: msg="This role is only supported on Debian buster"
-  when: not (ansible_distribution == 'Debian' and ansible_distribution_release == 'buster')
-
 - name: Install prometheus
   apt: name=prometheus
 
@@ -25,6 +21,13 @@
   - Reload systemd
   - Restart prometheus-pve-exporter
 
+- name: Configure prometheus retention
+  lineinfile:
+    path: /etc/default/prometheus
+    regexp: '^ARGS=.*$'
+    line: 'ARGS="--storage.tsdb.retention.time=365d"'
+  notify: Restart prometheus
+
 - name: Configure prometheus
   template: src=prometheus.yml.j2 dest=/etc/prometheus/prometheus.yml
   notify: Restart prometheus