Monitor: keep checking interfaces whose link-down alert is still open

After the interface baseline is reset, a port that is already down reads as
"first seen down", which neither alerts nor resolves. An alert opened before
the reset was then stuck open without updates: micro1's enp3s0 had sat at
one failed check since March with no ticket. An interface with an open
interface_down alert is now treated as previously up, so the alert keeps
counting, tickets and resolves as normal.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

monitor.py

@@ -1195,6 +1195,10 @@ class NetworkMonitor:
     def _process_interfaces(self, states: Dict[str, Dict[str, bool]], suppressions: list) -> None:
         baseline = db.get_baseline()
         new_baseline = {k: dict(v) for k, v in baseline.items()}
+        # An interface with an open link-down alert was up before it went down, whatever the
+        # baseline says now: after a baseline reset it reads as "first seen down", which would
+        # leave the alert open forever without updating, ticketing or resolving it.
+        open_down = set(db.get_open_event_targets('interface_down'))
         # Only count hosts with genuine regressions (UP→DOWN) toward cluster threshold
         hosts_with_regression: List[str] = []
 
@@ -1207,6 +1211,8 @@ class NetworkMonitor:
 
             for iface, is_up in ifaces.items():
                 prev = baseline.get(host, {}).get(iface)  # 'up', 'initial_down', or None
+                if (host, iface) in open_down:
+                    prev = 'up'
 
                 if is_up:
                     new_baseline[host][iface] = 'up'

tests/test_monitor.py

@@ -31,6 +31,7 @@ def db():
         mock_db.cutsheet_load.return_value = {'items': [], 'cables': [], 'port_labels': []}
         mock_db.get_pending_recovery_notes.return_value = []
         mock_db.get_device_link.return_value = ''
+        mock_db.get_open_event_targets.return_value = []
         yield mock_db
 
 
@@ -117,6 +118,24 @@ class TestDeadHostDetection:
         mon._process_interfaces({HOST_A: {'eth0': True}}, [])
         assert ('cluster_network_issue', 'test-cluster', '') in upserted(db)
 
+    def test_open_alert_survives_a_baseline_reset(self, mon, db):
+        # The baseline lost eth1 (reset), but its link-down alert is still open: keep alerting
+        db.get_open_event_targets.return_value = [('alpha', 'eth1')]
+        db.upsert_event.return_value = (3, False, 2, None)
+        mon._process_interfaces({HOST_A: {'eth0': True, 'eth1': False}, HOST_B: {'eth0': True}}, [])
+        assert ('interface_down', 'alpha', 'eth1') in upserted(db)
+        assert 'Interface eth1 link-down' in mon.tickets.create.call_args.args[0]
+
+    def test_open_alert_resolves_when_the_link_returns(self, mon, db):
+        db.get_open_event_targets.return_value = [('alpha', 'eth1')]
+        mon._process_interfaces({HOST_A: {'eth0': True, 'eth1': True}, HOST_B: {'eth0': True}}, [])
+        db.resolve_event.assert_any_call('interface_down', 'alpha', 'eth1')
+
+    def test_first_seen_down_without_an_alert_still_stays_quiet(self, mon, db):
+        db.get_open_event_targets.return_value = []
+        mon._process_interfaces({HOST_A: {'eth0': True, 'eth1': False}, HOST_B: {'eth0': True}}, [])
+        assert ('interface_down', 'alpha', 'eth1') not in upserted(db)
+
     def test_dead_host_shows_as_down_on_dashboard(self, mon):
         snap = mon._collect_snapshot({HOST_A: {'eth0': True}})
         assert snap['hosts']['alpha']['status'] == 'up'