Warn when autoremove is possible

roles/prometheus-node-exporter/files/apt.sh

@@ -16,7 +16,7 @@ upgrades="$(/usr/bin/apt-get --just-print dist-upgrade \
 )"
 
 autoremove="$(/usr/bin/apt-get --just-print autoremove \
-  | /usr/bin/awk '/^Remv/{a++}END{print "apt_autoremove_pending " a}'
+  | /usr/bin/awk '/^Remv/{a++}END{printf "apt_autoremove_pending %d", a}'
 )"
 
 echo '# HELP apt_upgrades_pending Apt package pending updates by origin.'
@@ -29,11 +29,7 @@ fi
 
 echo '# HELP apt_autoremove_pending Apt package pending autoremove.'
 echo '# TYPE apt_autoremove_pending gauge'
-if [[ -n "${autoremove}" ]] ; then
-  echo "${autoremove}"
-else
-  echo 'apt_autoremove_pending 0'
-fi
+echo "${autoremove}"
 
 echo '# HELP node_reboot_required Node reboot is required for software updates.'
 echo '# TYPE node_reboot_required gauge'

roles/prometheus/templates/prometheus/alert.rules.yml.j2

@@ -142,6 +142,14 @@ groups:
       summary: "La tension de sortie de {{ $labels.instance }} est de {{ $value }}V."
       description: "https://grafana.crans.org/d/qtbg59mZz/alimentation"
 
+  - alert: AptAutoremovePending
+    expr: apt_autoremove_pending > 0
+    for: 5m
+    labels:
+      severity: warning
+    annotations:
+      summary: "{{ $value }} paquet(s) APT sont inutile(s) sur {{ $labels.instance }}."
+
   # NTP (need NTP plugin in node)
 #  - alert: ntp_drifting
 #    expr: node_ntp_drift_seconds > 0.05