[prometheus-node] Use backports package

roles/prometheus-node/tasks/main.yml

@@ -3,9 +3,26 @@
   apt:
     update_cache: true
     name: prometheus-node-exporter
+    install_recommends: no  # Do not install smartmontools
   register: apt_result
   retries: 3
   until: apt_result is succeeded
+  when:
+    - ansible_lsb.codename == 'buster'
+
+# Prometheus 2 node is in stretch-backports
+- name: Install Prometheus node-exporter (stretch-backports)
+  apt:
+    update_cache: true
+    name: prometheus-node-exporter
+    install_recommends: no
+    state: latest
+    default_release: stretch-backports
+  register: apt_result
+  retries: 3
+  until: apt_result is succeeded
+  when:
+    - ansible_lsb.codename == 'stretch'
 
 - name: Activate prometheus-node-exporter service
   systemd:
@@ -13,12 +30,11 @@
     enabled: yes
     state: started
 
-# Doesn't work on Debian Stretch
+# Doesn't work on Debian Stretch with the old prometheus package
 - name: Make Prometheus node-exporter listen on adm only
-  when:
-    - ansible_lsb.codename == 'buster'
   lineinfile:
     path: /etc/default/prometheus-node-exporter
     regexp: '^ARGS='
     line: "ARGS=\"--web.listen-address={{ ansible_hostname }}.adm.crans.org:9100\""
   notify: Restart prometheus-node-exporter
+