Enumerate available states in Prometheus startup (#97993)

homeassistant/components/prometheus/__init__.py

@@ -120,10 +120,15 @@ def setup(hass: HomeAssistant, config: ConfigType) -> bool:
         default_metric,
     )
 
-    hass.bus.listen(EVENT_STATE_CHANGED, metrics.handle_state_changed)
+    hass.bus.listen(EVENT_STATE_CHANGED, metrics.handle_state_changed_event)
     hass.bus.listen(
         EVENT_ENTITY_REGISTRY_UPDATED, metrics.handle_entity_registry_updated
     )
+
+    for state in hass.states.all():
+        if entity_filter(state.entity_id):
+            metrics.handle_state(state)
+
     return True
 
 
@@ -162,16 +167,13 @@ class PrometheusMetrics:
         self._metrics = {}
         self._climate_units = climate_units
 
-    def handle_state_changed(self, event):
-        """Listen for new messages on the bus, and add them to Prometheus."""
+    def handle_state_changed_event(self, event):
+        """Handle new messages from the bus."""
         if (state := event.data.get("new_state")) is None:
             return
 
-        entity_id = state.entity_id
-        _LOGGER.debug("Handling state update for %s", entity_id)
-        domain, _ = hacore.split_entity_id(entity_id)
-
         if not self._filter(state.entity_id):
+            _LOGGER.debug("Filtered out entity %s", state.entity_id)
             return
 
         if (old_state := event.data.get("old_state")) is not None and (
@@ -179,6 +181,14 @@ class PrometheusMetrics:
         ) != state.attributes.get(ATTR_FRIENDLY_NAME):
             self._remove_labelsets(old_state.entity_id, old_friendly_name)
 
+        self.handle_state(state)
+
+    def handle_state(self, state):
+        """Add/update a state in Prometheus."""
+        entity_id = state.entity_id
+        _LOGGER.debug("Handling state update for %s", entity_id)
+        domain, _ = hacore.split_entity_id(entity_id)
+
         ignored_states = (STATE_UNAVAILABLE, STATE_UNKNOWN)
 
         handler = f"_handle_{domain}"

tests/components/prometheus/test_init.py

@@ -107,6 +107,34 @@ async def generate_latest_metrics(client):
     return body
 
 
+@pytest.mark.parametrize("namespace", [""])
+async def test_setup_enumeration(hass, hass_client, entity_registry, namespace):
+    """Test that setup enumerates existing states/entities."""
+
+    # The order of when things are created must be carefully controlled in
+    # this test, so we don't use fixtures.
+
+    sensor_1 = entity_registry.async_get_or_create(
+        domain=sensor.DOMAIN,
+        platform="test",
+        unique_id="sensor_1",
+        unit_of_measurement=UnitOfTemperature.CELSIUS,
+        original_device_class=SensorDeviceClass.TEMPERATURE,
+        suggested_object_id="outside_temperature",
+        original_name="Outside Temperature",
+    )
+    set_state_with_entry(hass, sensor_1, 12.3, {})
+    assert await async_setup_component(hass, prometheus.DOMAIN, {prometheus.DOMAIN: {}})
+
+    client = await hass_client()
+    body = await generate_latest_metrics(client)
+    assert (
+        'homeassistant_sensor_temperature_celsius{domain="sensor",'
+        'entity="sensor.outside_temperature",'
+        'friendly_name="Outside Temperature"} 12.3' in body
+    )
+
+
 @pytest.mark.parametrize("namespace", [""])
 async def test_view_empty_namespace(client, sensor_entities) -> None:
     """Test prometheus metrics view."""