Generate large history responses in the executor (#89606)

homeassistant/components/history/websocket_api.py

@@ -189,21 +189,78 @@ def _async_send_empty_response(
     """Send an empty response when we know all results are filtered away."""
     connection.send_result(msg_id)
     stream_end_time = end_time or dt_util.utcnow()
-    _async_send_response(connection, msg_id, start_time, stream_end_time, {})
+    connection.send_message(
+        _generate_websocket_response(msg_id, start_time, stream_end_time, {})
+    )
 
 
-@callback
-def _async_send_response(
-    connection: ActiveConnection,
+def _generate_websocket_response(
     msg_id: int,
     start_time: dt,
     end_time: dt,
     states: MutableMapping[str, list[dict[str, Any]]],
-) -> None:
-    """Send a response."""
-    empty_stream_message = _generate_stream_message(states, start_time, end_time)
-    empty_response = messages.event_message(msg_id, empty_stream_message)
-    connection.send_message(JSON_DUMP(empty_response))
+) -> str:
+    """Generate a websocket response."""
+    return JSON_DUMP(
+        messages.event_message(
+            msg_id, _generate_stream_message(states, start_time, end_time)
+        )
+    )
+
+
+def _generate_historical_response(
+    hass: HomeAssistant,
+    msg_id: int,
+    start_time: dt,
+    end_time: dt,
+    entity_ids: list[str] | None,
+    filters: Filters | None,
+    include_start_time_state: bool,
+    significant_changes_only: bool,
+    minimal_response: bool,
+    no_attributes: bool,
+    send_empty: bool,
+) -> tuple[float, dt | None, str | None]:
+    """Generate a historical response."""
+    states = cast(
+        MutableMapping[str, list[dict[str, Any]]],
+        history.get_significant_states(
+            hass,
+            start_time,
+            end_time,
+            entity_ids,
+            filters,
+            include_start_time_state,
+            significant_changes_only,
+            minimal_response,
+            no_attributes,
+            True,
+        ),
+    )
+    last_time_ts = 0.0
+    for state_list in states.values():
+        if (
+            state_list
+            and (state_last_time := state_list[-1][COMPRESSED_STATE_LAST_UPDATED])
+            > last_time_ts
+        ):
+            last_time_ts = cast(float, state_last_time)
+
+    if last_time_ts == 0:
+        # If we did not send any states ever, we need to send an empty response
+        # so the websocket client knows it should render/process/consume the
+        # data.
+        if not send_empty:
+            return last_time_ts, None, None
+        last_time_dt = end_time
+    else:
+        last_time_dt = dt_util.utc_from_timestamp(last_time_ts)
+
+    return (
+        last_time_ts,
+        last_time_dt,
+        _generate_websocket_response(msg_id, start_time, last_time_dt, states),
+    )
 
 
 async def _async_send_historical_states(
@@ -221,43 +278,24 @@ async def _async_send_historical_states(
     send_empty: bool,
 ) -> dt | None:
     """Fetch history significant_states and send them to the client."""
-    states = cast(
-        MutableMapping[str, list[dict[str, Any]]],
-        await get_instance(hass).async_add_executor_job(
-            history.get_significant_states,
-            hass,
-            start_time,
-            end_time,
-            entity_ids,
-            filters,
-            include_start_time_state,
-            significant_changes_only,
-            minimal_response,
-            no_attributes,
-            True,
-        ),
+    instance = get_instance(hass)
+    last_time_ts, last_time_dt, payload = await instance.async_add_executor_job(
+        _generate_historical_response,
+        hass,
+        msg_id,
+        start_time,
+        end_time,
+        entity_ids,
+        filters,
+        include_start_time_state,
+        significant_changes_only,
+        minimal_response,
+        no_attributes,
+        send_empty,
     )
-    last_time = 0
-
-    for state_list in states.values():
-        if (
-            state_list
-            and (state_last_time := state_list[-1][COMPRESSED_STATE_LAST_UPDATED])
-            > last_time
-        ):
-            last_time = state_last_time
-
-    if last_time == 0:
-        # If we did not send any states ever, we need to send an empty response
-        # so the websocket client knows it should render/process/consume the
-        # data.
-        if not send_empty:
-            return None
-        last_time_dt = end_time
-    else:
-        last_time_dt = dt_util.utc_from_timestamp(last_time)
-    _async_send_response(connection, msg_id, start_time, last_time_dt, states)
-    return last_time_dt if last_time != 0 else None
+    if payload:
+        connection.send_message(payload)
+    return last_time_dt if last_time_ts != 0 else None
 
 
 def _history_compressed_state(state: State, no_attributes: bool) -> dict[str, Any]: