Install node-exporter from backports on stretch

node_exporter/tasks/main.yml

@@ -4,6 +4,17 @@
   apt:
     name: prometheus-node-exporter
     state: present
+  when: ansible_distribution_major_version|int >= 10
+  tags:
+    - prometheus
+    - prometheus-exporter
+
+- name: Install node_exporter (stretch)
+  apt:
+    name: prometheus-node-exporter
+    state: present
+    default_release: stretch-backports
+  when: ansible_distribution_major_version|int == 9
   tags:
     - prometheus
     - prometheus-exporter