Improve websocket throughput and reduce latency (#92967)

homeassistant/components/websocket_api/commands.py

@@ -715,7 +715,7 @@ def handle_supported_features(
     hass: HomeAssistant, connection: ActiveConnection, msg: dict[str, Any]
 ) -> None:
     """Handle setting supported features."""
-    connection.supported_features = msg["features"]
+    connection.set_supported_features(msg["features"])
     connection.send_result(msg["id"])
 
 

homeassistant/components/websocket_api/connection.py

@@ -48,6 +48,7 @@ class ActiveConnection:
         self.refresh_token_id = refresh_token.id
         self.subscriptions: dict[Hashable, Callable[[], Any]] = {}
         self.last_id = 0
+        self.can_coalesce = False
         self.supported_features: dict[str, float] = {}
         self.handlers: dict[str, tuple[MessageHandler, vol.Schema]] = self.hass.data[
             const.DOMAIN
@@ -55,6 +56,11 @@ class ActiveConnection:
         self.binary_handlers: list[BinaryHandler | None] = []
         current_connection.set(self)
 
+    def set_supported_features(self, features: dict[str, float]) -> None:
+        """Set supported features."""
+        self.supported_features = features
+        self.can_coalesce = const.FEATURE_COALESCE_MESSAGES in features
+
     def get_description(self, request: web.Request | None) -> str:
         """Return a description of the connection."""
         description = self.user.name or ""

homeassistant/components/websocket_api/http.py

@@ -2,6 +2,7 @@
 from __future__ import annotations
 
 import asyncio
+from collections import deque
 from collections.abc import Callable
 from contextlib import suppress
 import datetime as dt
@@ -22,7 +23,6 @@ from .auth import AuthPhase, auth_required_message
 from .const import (
     CANCELLATION_ERRORS,
     DATA_CONNECTIONS,
-    FEATURE_COALESCE_MESSAGES,
     MAX_PENDING_MSG,
     PENDING_MSG_PEAK,
     PENDING_MSG_PEAK_TIME,
@@ -71,7 +71,6 @@ class WebSocketHandler:
         self.hass = hass
         self.request = request
         self.wsock = web.WebSocketResponse(heartbeat=55)
-        self._to_write: asyncio.Queue = asyncio.Queue(maxsize=MAX_PENDING_MSG)
         self._handle_task: asyncio.Task | None = None
         self._writer_task: asyncio.Task | None = None
         self._closing: bool = False
@@ -79,6 +78,13 @@ class WebSocketHandler:
         self._peak_checker_unsub: Callable[[], None] | None = None
         self.connection: ActiveConnection | None = None
 
+        # The WebSocketHandler has a single consumer and path
+        # to where messages are queued. This allows the implementation
+        # to use a deque and an asyncio.Future to avoid the overhead of
+        # an asyncio.Queue.
+        self._message_queue: deque = deque()
+        self._ready_future: asyncio.Future[None] | None = None
+
     @property
     def description(self) -> str:
         """Return a description of the connection."""
@@ -88,39 +94,52 @@ class WebSocketHandler:
 
     async def _writer(self) -> None:
         """Write outgoing messages."""
-        # Exceptions if Socket disconnected or cancelled by connection handler
+        # Variables are set locally to avoid lookups in the loop
-        to_write = self._to_write
+        message_queue = self._message_queue
         logger = self._logger
-        wsock = self.wsock
+        send_str = self.wsock.send_str
+        loop = self.hass.loop
+        debug = logger.debug
+        # Exceptions if Socket disconnected or cancelled by connection handler
         try:
             with suppress(RuntimeError, ConnectionResetError, *CANCELLATION_ERRORS):
                 while not self.wsock.closed:
-                    if (process := await to_write.get()) is None:
+                    if (messages_remaining := len(message_queue)) == 0:
+                        self._ready_future = loop.create_future()
+                        await self._ready_future
+                        messages_remaining = len(message_queue)
+
+                    # A None message is used to signal the end of the connection
+                    if (process := message_queue.popleft()) is None:
                         return
+
+                    messages_remaining -= 1
                     message = process if isinstance(process, str) else process()
+
                     if (
-                        to_write.empty()
+                        not messages_remaining
                         or not self.connection
-                        or FEATURE_COALESCE_MESSAGES
+                        or not self.connection.can_coalesce
-                        not in self.connection.supported_features
                     ):
-                        logger.debug("Sending %s", message)
+                        debug("Sending %s", message)
-                        await wsock.send_str(message)
+                        await send_str(message)
                         continue
 
                     messages: list[str] = [message]
-                    while not to_write.empty():
+                    while messages_remaining:
-                        if (process := to_write.get_nowait()) is None:
+                        # A None message is used to signal the end of the connection
+                        if (process := message_queue.popleft()) is None:
                             return
                         messages.append(
                             process if isinstance(process, str) else process()
                         )
+                        messages_remaining -= 1
 
                     coalesced_messages = "[" + ",".join(messages) + "]"
-                    logger.debug("Sending %s", coalesced_messages)
+                    debug("Sending %s", coalesced_messages)
-                    await wsock.send_str(coalesced_messages)
+                    await send_str(coalesced_messages)
         finally:
-            # Clean up the peaker checker when we shut down the writer
+            # Clean up the peak checker when we shut down the writer
             self._cancel_peak_checker()
 
     @callback
@@ -146,11 +165,9 @@ class WebSocketHandler:
         if isinstance(message, dict):
             message = message_to_json(message)
 
-        to_write = self._to_write
+        message_queue = self._message_queue
-
+        queue_size_before_add = len(message_queue)
-        try:
+        if queue_size_before_add >= MAX_PENDING_MSG:
-            to_write.put_nowait(message)
-        except asyncio.QueueFull:
             self._logger.error(
                 (
                     "%s: Client unable to keep up with pending messages. Reached %s pending"
@@ -162,10 +179,15 @@ class WebSocketHandler:
                 message,
             )
             self._cancel()
+            return
+
+        message_queue.append(message)
+        if self._ready_future and not self._ready_future.done():
+            self._ready_future.set_result(None)
 
         peak_checker_active = self._peak_checker_unsub is not None
 
-        if to_write.qsize() < PENDING_MSG_PEAK:
+        if queue_size_before_add <= PENDING_MSG_PEAK:
             if peak_checker_active:
                 self._cancel_peak_checker()
             return
@@ -180,7 +202,7 @@ class WebSocketHandler:
         """Check that we are no longer above the write peak."""
         self._peak_checker_unsub = None
 
-        if self._to_write.qsize() < PENDING_MSG_PEAK:
+        if len(self._message_queue) < PENDING_MSG_PEAK:
             return
 
         self._logger.error(
@@ -199,6 +221,7 @@ class WebSocketHandler:
     def _cancel(self) -> None:
         """Cancel the connection."""
         self._closing = True
+        self._cancel_peak_checker()
         if self._handle_task is not None:
             self._handle_task.cancel()
         if self._writer_task is not None:
@@ -356,14 +379,14 @@ class WebSocketHandler:
 
             self._closing = True
 
+            self._message_queue.append(None)
+            if self._ready_future and not self._ready_future.done():
+                self._ready_future.set_result(None)
+
             try:
-                self._to_write.put_nowait(None)
                 # Make sure all error messages are written before closing
                 await self._writer_task
                 await wsock.close()
-            except asyncio.QueueFull:  # can be raised by put_nowait
-                self._writer_task.cancel()
-
             finally:
                 if disconnect_warn is None:
                     self._logger.debug("Disconnected")

tests/components/websocket_api/test_http.py

@@ -1,7 +1,7 @@
 """Test Websocket API http module."""
 import asyncio
 from datetime import timedelta
-from typing import Any
+from typing import Any, cast
 from unittest.mock import patch
 
 from aiohttp import ServerDisconnectedError, WSMsgType, web
@@ -53,12 +53,12 @@ async def test_pending_msg_peak(
 ) -> None:
     """Test pending msg overflow command."""
     orig_handler = http.WebSocketHandler
-    instance = None
+    setup_instance: http.WebSocketHandler | None = None
 
     def instantiate_handler(*args):
-        nonlocal instance
+        nonlocal setup_instance
-        instance = orig_handler(*args)
+        setup_instance = orig_handler(*args)
-        return instance
+        return setup_instance
 
     with patch(
         "homeassistant.components.websocket_api.http.WebSocketHandler",
@@ -66,11 +66,10 @@ async def test_pending_msg_peak(
     ):
         websocket_client = await hass_ws_client()
 
-    # Kill writer task and fill queue past peak
+    instance: http.WebSocketHandler = cast(http.WebSocketHandler, setup_instance)
-    for _ in range(5):
-        instance._to_write.put_nowait(None)
 
-    # Trigger the peak check
+    # Fill the queue past the allowed peak
+    for _ in range(10):
         instance._send_message({})
 
     async_fire_time_changed(
@@ -79,8 +78,54 @@ async def test_pending_msg_peak(
 
     msg = await websocket_client.receive()
     assert msg.type == WSMsgType.close
-
     assert "Client unable to keep up with pending messages" in caplog.text
+    assert "Stayed over 5 for 5 seconds"
+
+
+async def test_pending_msg_peak_recovery(
+    hass: HomeAssistant,
+    mock_low_peak,
+    hass_ws_client: WebSocketGenerator,
+    caplog: pytest.LogCaptureFixture,
+) -> None:
+    """Test pending msg nears the peak but recovers."""
+    orig_handler = http.WebSocketHandler
+    setup_instance: http.WebSocketHandler | None = None
+
+    def instantiate_handler(*args):
+        nonlocal setup_instance
+        setup_instance = orig_handler(*args)
+        return setup_instance
+
+    with patch(
+        "homeassistant.components.websocket_api.http.WebSocketHandler",
+        instantiate_handler,
+    ):
+        websocket_client = await hass_ws_client()
+
+    instance: http.WebSocketHandler = cast(http.WebSocketHandler, setup_instance)
+
+    # Make sure the call later is started
+    for _ in range(10):
+        instance._send_message({})
+
+    for _ in range(10):
+        msg = await websocket_client.receive()
+        assert msg.type == WSMsgType.TEXT
+
+    instance._send_message({})
+    msg = await websocket_client.receive()
+    assert msg.type == WSMsgType.TEXT
+
+    # Cleanly shutdown
+    instance._send_message({})
+    instance._handle_task.cancel()
+
+    msg = await websocket_client.receive()
+    assert msg.type == WSMsgType.TEXT
+    msg = await websocket_client.receive()
+    assert msg.type == WSMsgType.close
+    assert "Client unable to keep up with pending messages" not in caplog.text
 
 
 async def test_pending_msg_peak_but_does_not_overflow(
@@ -91,12 +136,12 @@ async def test_pending_msg_peak_but_does_not_overflow(
 ) -> None:
     """Test pending msg hits the low peak but recovers and does not overflow."""
     orig_handler = http.WebSocketHandler
-    instance: http.WebSocketHandler | None = None
+    setup_instance: http.WebSocketHandler | None = None
 
     def instantiate_handler(*args):
-        nonlocal instance
+        nonlocal setup_instance
-        instance = orig_handler(*args)
+        setup_instance = orig_handler(*args)
-        return instance
+        return setup_instance
 
     with patch(
         "homeassistant.components.websocket_api.http.WebSocketHandler",
@@ -104,18 +149,17 @@ async def test_pending_msg_peak_but_does_not_overflow(
     ):
         websocket_client = await hass_ws_client()
 
-    assert instance is not None
+    instance: http.WebSocketHandler = cast(http.WebSocketHandler, setup_instance)
 
     # Kill writer task and fill queue past peak
     for _ in range(5):
-        instance._to_write.put_nowait(None)
+        instance._message_queue.append(None)
 
     # Trigger the peak check
     instance._send_message({})
 
     # Clear the queue
-    while instance._to_write.qsize() > 0:
+    instance._message_queue.clear()
-        instance._to_write.get_nowait()
 
     # Trigger the peak clear
     instance._send_message({})