bundles/smartd: add cronjob to schedule a monthly long test

bundles/smartd/metadata.py

@@ -66,7 +66,7 @@ def telegraf(metadata):
     if not node.has_bundle('telegraf'):
         raise DoNotRunAgain
 
-    if metadata.get('smartd/disks', {}):
+    if metadata.get('smartd/disks', set()):
         return {
             'telegraf': {
                 'input_plugins': {
@@ -80,3 +80,22 @@ def telegraf(metadata):
         }
 
     return {}
+
+
+@metadata_reactor.provides(
+    'cron/smartd',
+)
+def monthly_long_test(metadata):
+    lines = set()
+
+    for number, disk in enumerate(sorted(metadata.get('smartd/disks', set()))):
+        lines.add('0 3 {} * *    root    /usr/sbin/smartctl --test=long {} >/dev/null'.format(
+            number+1, # enumerate() starts at 0
+            disk,
+        ))
+
+    return {
+        'cron': {
+            'smartd': '\n'.join(sorted(lines)),
+        },
+    }