Dashboard cards, backup last-seen

plugins/backups/models/backup.py

@@ -89,6 +89,16 @@ class BackupRevision(db.Model):
 
     createdat = db.Column(db.DateTime, nullable=False, default=datetime.utcnow)
 
+    # When this configuration was last CONFIRMED still current, which is not the
+    # same as when it last changed. Dedup means an unchanged config writes no
+    # revision, so collectedat only ever moves on a change - a machine whose
+    # settings have been stable for six months has a six-month-old newest
+    # revision and is perfectly healthy. Without this column ShopDB cannot tell
+    # that machine from one whose backup stopped running six months ago, which
+    # is the one question a backup system has to be able to answer. Touched on
+    # every matching post, including the no-op that writes nothing else.
+    lastseenat = db.Column(db.DateTime, nullable=True)
+
     __table_args__ = (
         db.Index('ixbackuprevisionsassetkind', 'assetid', 'backupkind'),
     )
@@ -138,6 +148,10 @@ class BackupRevision(db.Model):
             # BROWSER-LOCAL and the timestamp silently shifts by the viewer's
             # offset before any site-timezone formatting is applied.
             'collectedat': _utciso(self.collectedat),
+            # When the config was last CONFIRMED current, versus when it last
+            # changed. The history view needs both or a stable machine looks
+            # abandoned.
+            'lastseenat': _utciso(self.lastseenat),
             'createdat': _utciso(self.createdat),
         }
         if includepayload: