drop a camera's cached frame mappings when it is removed or recreated

A reader that kept its mappings open stayed on a removed camera's segments, which pinned their shared memory until restart, and after a same-size recreate the ledger reopen only refreshed the slot being read while the other cached slots still returned the old camera's pixels. Readers now drop every cached slot for a camera on its remove update, and get() does the same when a ledger mismatch turns out to be a replaced ledger rather than a lapped slot.

frigate/embeddings/maintainer.py

@@ -332,6 +332,9 @@ class EmbeddingMaintainer(threading.Thread):
         """Apply camera config updates and register newly enabled processors."""
         updated_topics = self.config_updater.check_for_updates()
 
+        for camera in updated_topics.get("remove", []):
+            self.frame_manager.close_camera(camera)
+
         if updated_topics.keys() & GENAI_UPDATE_TOPICS:
             self._sync_genai_processors()
 

frigate/output/output.py

@@ -145,6 +145,7 @@ class OutputProcess(FrigateProcess):
                 CameraConfigUpdateEnum.birdseye,
                 CameraConfigUpdateEnum.enabled,
                 CameraConfigUpdateEnum.record,
+                CameraConfigUpdateEnum.remove,
             ],
         )
         birdseye_config_subscriber = ConfigSubscriber("config/birdseye", exact=True)
@@ -208,6 +209,10 @@ class OutputProcess(FrigateProcess):
                             birdseye,
                         )
 
+            if CameraConfigUpdateEnum.remove in updates:
+                for camera in updates["remove"]:
+                    frame_manager.close_camera(camera)
+
             _result = detection_subscriber.check_for_update(timeout=1)
             if _result is None:
                 continue

frigate/review/maintainer.py

@@ -504,6 +504,7 @@ class ReviewSegmentMaintainer(threading.Thread):
     def _handle_camera_removed(self, camera: str) -> None:
         """Close out a deleted camera's segment so a reused name cannot inherit it."""
         self.forcibly_end_segment(camera)
+        self.frame_manager.close_camera(camera)
         self.indefinite_events.pop(camera, None)
         self.recent_classification_state_changes.pop(camera, None)
 

frigate/test/test_camera_lifecycle.py

@@ -183,10 +183,12 @@ class TestReviewMaintainerRemoval(unittest.TestCase):
             "deleted_cam": [{"model": "gate", "from": "a", "to": "b", "timestamp": 1.0}]
         }
         maintainer.forcibly_end_segment = MagicMock()
+        maintainer.frame_manager = MagicMock()
 
         maintainer._handle_camera_removed("deleted_cam")
 
         maintainer.forcibly_end_segment.assert_called_once_with("deleted_cam")
+        maintainer.frame_manager.close_camera.assert_called_once_with("deleted_cam")
         self.assertNotIn("deleted_cam", maintainer.indefinite_events)
         self.assertNotIn("deleted_cam", maintainer.recent_classification_state_changes)
 

frigate/test/test_shared_memory_frame_manager.py

@@ -243,26 +243,56 @@ class TestSharedMemoryFrameManagerFrameTimes(unittest.TestCase):
 
         self.assertIsNone(arr)
 
-    def test_get_reopens_once_when_cached_ledger_is_stale(self) -> None:
+    def test_get_reopens_every_cached_slot_when_ledger_is_stale(self) -> None:
         """A camera recreated at the same resolution gets new segments under
-        the old names. A long-lived reader still mapped to the unlinked
+        the old names. A long-lived reader still mapped to the unlinked ledger
-        ledger sees a mismatch, which must trigger one reopen by name before
+        sees a mismatch, which must drop every cached slot of that camera, not
-        the frame is declared gone."""
+        only the one being read, or later reads return the old pixels."""
         manager = SharedMemoryFrameManager()
-        stale = _segments(cam_frame0=2_500, cam_frame_times=8 * 2)
+        stale = _segments(cam_frame0=2_500, cam_frame1=2_500, cam_frame_times=8 * 2)
         manager.shm_store.update(stale)
-        current = _segments(cam_frame0=2_500, cam_frame_times=8 * 2)
+        current = _segments(cam_frame0=2_500, cam_frame1=2_500, cam_frame_times=8 * 2)
-        np.frombuffer(current["cam_frame_times"].buf, dtype=np.float64)[0] = 100.25
+        current["cam_frame1"].buf[0] = 7
+        np.frombuffer(current["cam_frame_times"].buf, dtype=np.float64)[:] = (
+            100.25,
+            100.5,
+        )
 
         with patch(
             "frigate.util.image.UntrackedSharedMemory",
             side_effect=_open_from(current),
+        ):
+            first = manager.get("cam_frame0", (50, 50), frame_time=100.25)
+            second = manager.get("cam_frame1", (50, 50), frame_time=100.5)
+
+        self.assertIsNotNone(first)
+        self.assertEqual(second[0, 0], 7)
+        self.assertIs(manager.shm_store["cam_frame1"], current["cam_frame1"])
+
+    def test_get_keeps_cached_slots_when_only_lapped(self) -> None:
+        manager = SharedMemoryFrameManager()
+        segments = _segments(cam_frame0=2_500, cam_frame1=2_500, cam_frame_times=8 * 2)
+        manager.shm_store.update(segments)
+        np.frombuffer(segments["cam_frame_times"].buf, dtype=np.float64)[0] = 200.0
+
+        with patch(
+            "frigate.util.image.UntrackedSharedMemory",
+            side_effect=_open_from(segments),
         ):
             arr = manager.get("cam_frame0", (50, 50), frame_time=100.25)
 
-        self.assertIsNotNone(arr)
+        self.assertIsNone(arr)
-        self.assertIs(manager.shm_store["cam_frame0"], current["cam_frame0"])
+        self.assertIs(manager.shm_store["cam_frame1"], segments["cam_frame1"])
-        self.assertIs(manager.shm_store["cam_frame_times"], current["cam_frame_times"])
+
+    def test_close_camera_drops_only_that_camera(self) -> None:
+        manager = SharedMemoryFrameManager()
+        manager.shm_store.update(
+            _segments(cam_frame0=1, cam_frame1=1, cam_frame_times=8, other_frame0=1)
+        )
+
+        manager.close_camera("cam")
+
+        self.assertEqual(set(manager.shm_store), {"other_frame0"})
 
     def test_get_without_frame_time_skips_ledger(self) -> None:
         manager = SharedMemoryFrameManager()

frigate/track/object_processing.py

@@ -763,6 +763,7 @@ class TrackedObjectProcessor(threading.Thread):
                         continue
 
                     camera_state.shutdown()
+                    self.frame_manager.close_camera(camera)
 
                     with self.camera_states_lock:
                         self.camera_states.pop(camera)

frigate/util/image.py

@@ -1003,6 +1003,10 @@ class FrameManager(ABC):
     def close(self, name: str):
         pass
 
+    @abstractmethod
+    def close_camera(self, camera: str) -> None:
+        pass
+
     @abstractmethod
     def delete(self, name: str):
         pass
@@ -1110,7 +1114,8 @@ class SharedMemoryFrameManager(FrameManager):
         """Map a frame slot as an array without copying it.
 
         The array points into shared memory, so it is only valid until the next
-        close(), delete(), or get() of the same name. Copy it to keep it longer.
+        close(), delete(), or get() of the same name, and capture overwrites its
+        pixels once the ring wraps back to this slot. Copy it to keep it longer.
 
         Args:
             name: Slot name, such as front_door_frame3
@@ -1122,15 +1127,18 @@ class SharedMemoryFrameManager(FrameManager):
             a different frame than frame_time
         """
         if frame_time is not None and not self._holds(name, frame_time):
-            # a mapping left over from a same-size recreate of the camera
+            # a ledger left over from a same-size recreate of the camera looks
-            # looks the same as a lapped slot, so reopen by name once
+            # the same as a lapped slot, so reopen it by name once
-            self.close(name)
+            camera = name.rpartition("_frame")[0]
-            self.close(f"{name.rpartition('_frame')[0]}_frame_times")
+            self.close(f"{camera}_frame_times")
 
             if not self._holds(name, frame_time):
                 logger.debug("%s no longer holds the frame from %s", name, frame_time)
                 return None
 
+            # the ledger was replaced, so every cached slot maps the old segments
+            self.close_camera(camera)
+
         try:
             required = int(np.prod(shape))
             shm = self.shm_store.get(name)
@@ -1161,6 +1169,11 @@ class SharedMemoryFrameManager(FrameManager):
             self.shm_store[name].close()
             del self.shm_store[name]
 
+    def close_camera(self, camera: str) -> None:
+        """Drop every cached mapping for a camera's frame ring and ledger."""
+        for name in [n for n in self.shm_store if n.startswith(f"{camera}_frame")]:
+            self.close(name)
+
     def delete(self, name: str):
         if name in self.shm_store:
             self.shm_store[name].close()