better error handling, true async sending, more readable api

freqtrade/rpc/api_server/api_ws.py

@@ -1,16 +1,14 @@
-import asyncio
 import logging
 from typing import Any, Dict
 
 from fastapi import APIRouter, Depends
-from fastapi.websockets import WebSocket, WebSocketDisconnect
+from fastapi.websockets import WebSocket
 from pydantic import ValidationError
-from websockets.exceptions import ConnectionClosed
 
 from freqtrade.enums import RPCMessageType, RPCRequestType
 from freqtrade.rpc.api_server.api_auth import validate_ws_token
 from freqtrade.rpc.api_server.deps import get_message_stream, get_rpc
-from freqtrade.rpc.api_server.ws import WebSocketChannel
+from freqtrade.rpc.api_server.ws.channel import WebSocketChannel, create_channel
 from freqtrade.rpc.api_server.ws.message_stream import MessageStream
 from freqtrade.rpc.api_server.ws_schemas import (WSAnalyzedDFMessage, WSMessageSchema,
                                                  WSRequestSchema, WSWhitelistMessage)
@@ -23,45 +21,20 @@ logger = logging.getLogger(__name__)
 router = APIRouter()
 
 
-class WebSocketChannelClosed(Exception):
-    """
-    General WebSocket exception to signal closing the channel
-    """
-    pass
-
-
 async def channel_reader(channel: WebSocketChannel, rpc: RPC):
     """
     Iterate over the messages from the channel and process the request
     """
-    try:
     async for message in channel:
         await _process_consumer_request(message, channel, rpc)
-    except (
-        RuntimeError,
-        WebSocketDisconnect,
-        ConnectionClosed
-    ):
-        raise WebSocketChannelClosed
-    except asyncio.CancelledError:
-        return
 
 
 async def channel_broadcaster(channel: WebSocketChannel, message_stream: MessageStream):
     """
     Iterate over messages in the message stream and send them
     """
-    try:
     async for message in message_stream:
         await channel.send(message)
-    except (
-        RuntimeError,
-        WebSocketDisconnect,
-        ConnectionClosed
-    ):
-        raise WebSocketChannelClosed
-    except asyncio.CancelledError:
-        return
 
 
 async def _process_consumer_request(
@@ -103,15 +76,11 @@ async def _process_consumer_request(
 
         # Format response
         response = WSWhitelistMessage(data=whitelist)
-        # Send it back
         await channel.send(response.dict(exclude_none=True))
 
     elif type == RPCRequestType.ANALYZED_DF:
-        limit = None
-
-        if data:
         # Limit the amount of candles per dataframe to 'limit' or 1500
-            limit = max(data.get('limit', 1500), 1500)
+        limit = min(data.get('limit', 1500), 1500) if data else None
 
         # For every pair in the generator, send a separate message
         for message in rpc._ws_request_analyzed_df(limit):
@@ -127,17 +96,8 @@ async def message_endpoint(
     rpc: RPC = Depends(get_rpc),
     message_stream: MessageStream = Depends(get_message_stream)
 ):
-    async with WebSocketChannel(websocket).connect() as channel:
-        try:
-            logger.info(f"Channel connected - {channel}")
-
-            channel_tasks = asyncio.gather(
+    async with create_channel(websocket) as channel:
+        await channel.run_channel_tasks(
             channel_reader(channel, rpc),
             channel_broadcaster(channel, message_stream)
         )
-            await channel_tasks
-        except WebSocketChannelClosed:
-            pass
-        finally:
-            logger.info(f"Channel disconnected - {channel}")
-            channel_tasks.cancel()

freqtrade/rpc/api_server/webserver.py

@@ -94,6 +94,7 @@ class ApiServer(RPCHandler):
         del ApiServer._rpc
         if self._server and not self._standalone:
             logger.info("Stopping API Server")
+            # self._server.force_exit, self._server.should_exit = True, True
             self._server.cleanup()
 
     @classmethod

freqtrade/rpc/api_server/ws/channel.py

@@ -29,6 +29,7 @@ class WebSocketChannel:
 
         # Internal event to signify a closed websocket
         self._closed = asyncio.Event()
+        self._send_timeout_high_limit = 2
 
         # The subscribed message types
         self._subscriptions: List[str] = []
@@ -36,6 +37,9 @@ class WebSocketChannel:
         # Wrap the WebSocket in the Serializing class
         self._wrapped_ws = serializer_cls(self._websocket)
 
+        # The async tasks created for the channel
+        self._channel_tasks: List[asyncio.Task] = []
+
     def __repr__(self):
         return f"WebSocketChannel({self.channel_id}, {self.remote_addr})"
 
@@ -51,7 +55,14 @@ class WebSocketChannel:
         """
         Send a message on the wrapped websocket
         """
-        await self._wrapped_ws.send(message)
+
+        # Without this sleep, messages would send to one channel
+        # first then another after the first one finished.
+        # With the sleep call, it gives control to the event
+        # loop to schedule other channel send methods.
+        await asyncio.sleep(0)
+
+        return await self._wrapped_ws.send(message)
 
     async def recv(self):
         """
@@ -77,7 +88,6 @@ class WebSocketChannel:
         """
 
         self._closed.set()
-        self._relay_task.cancel()
 
         try:
             await self._websocket.close()
@@ -106,23 +116,68 @@ class WebSocketChannel:
         """
         return message_type in self._subscriptions
 
+    async def run_channel_tasks(self, *tasks, **kwargs):
+        """
+        Create and await on the channel tasks unless an exception
+        was raised, then cancel them all.
+
+        :params *tasks: All coros or tasks to be run concurrently
+        :param **kwargs: Any extra kwargs to pass to gather
+        """
+
+        # Wrap the coros into tasks if they aren't already
+        self._channel_tasks = [
+            task if isinstance(task, asyncio.Task) else asyncio.create_task(task)
+            for task in tasks
+        ]
+
+        try:
+            await asyncio.gather(*self._channel_tasks, **kwargs)
+        except Exception:
+            # If an exception occurred, cancel the rest of the tasks and bubble up
+            # the error that was caught here
+            await self.cancel_channel_tasks()
+            raise
+
+    async def cancel_channel_tasks(self):
+        """
+        Cancel and wait on all channel tasks
+        """
+        for task in self._channel_tasks:
+            task.cancel()
+
+        # Wait for tasks to finish cancelling
+        try:
+            await asyncio.wait(self._channel_tasks)
+        except asyncio.CancelledError:
+            pass
+
+        self._channel_tasks = []
+
     async def __aiter__(self):
         """
         Generator for received messages
         """
-        while True:
-            try:
+        # We can not catch any errors here as websocket.recv is
+        # the first to catch any disconnects and bubble it up
+        # so the connection is garbage collected right away
+        while not self.is_closed():
             yield await self.recv()
-            except Exception:
-                break
+
 
 @asynccontextmanager
-    async def connect(self):
+async def create_channel(websocket: WebSocketType, **kwargs):
     """
-        Context manager for safely opening and closing the websocket connection
+    Context manager for safely opening and closing a WebSocketChannel
     """
+    channel = WebSocketChannel(websocket, **kwargs)
     try:
-            await self.accept()
-            yield self
+        await channel.accept()
+        logger.info(f"Connected to channel - {channel}")
+
+        yield channel
+    except Exception:
+        pass
     finally:
-            await self.close()
+        await channel.close()
+        logger.info(f"Disconnected from channel - {channel}")

freqtrade/rpc/api_server/ws/message_stream.py

@@ -17,7 +17,8 @@ class MessageStream:
     async def subscribe(self):
         waiter = self._waiter
         while True:
-            message, waiter = await waiter
+            # Shield the future from being cancelled by a task waiting on it
+            message, waiter = await asyncio.shield(waiter)
             yield message
 
     __aiter__ = subscribe