feat: 实现 RPC 服务器的发送队列和背压控制机制

src/plugin_runtime/host/rpc_server.py

@@ -10,6 +10,7 @@
 from typing import Any, Awaitable, Callable, Dict, List, Optional, Tuple
 
 import asyncio
+import contextlib
 import secrets
 
 from src.common.logger import get_logger
@@ -67,7 +68,8 @@ class RPCServer:
         self._pending_requests: Dict[int, Tuple[asyncio.Future, int]] = {}
 
         # 发送队列（背压控制）
-        self._send_queue: Optional[asyncio.Queue[bytes]] = None
+        self._send_queue: Optional[asyncio.Queue[Tuple[Connection, bytes, asyncio.Future[None]]]] = None
+        self._send_worker_task: Optional[asyncio.Task] = None
 
         # 运行状态
         self._running: bool = False
@@ -164,6 +166,7 @@ class RPCServer:
         """启动 RPC 服务器"""
         self._running = True
         self._send_queue = asyncio.Queue(maxsize=self._send_queue_size)
+        self._send_worker_task = asyncio.create_task(self._send_loop())
         await self._transport.start(self._handle_connection)
         logger.info(f"RPC Server 已启动，监听地址: {self._transport.get_address()}")
 
@@ -177,6 +180,14 @@ class RPCServer:
                 future.set_exception(RPCError(ErrorCode.E_TIMEOUT, "服务器关闭"))
         self._pending_requests.clear()
 
+        self._fail_queued_sends(ErrorCode.E_TIMEOUT, "服务器关闭")
+
+        if self._send_worker_task:
+            self._send_worker_task.cancel()
+            with contextlib.suppress(asyncio.CancelledError):
+                await self._send_worker_task
+            self._send_worker_task = None
+
         # 取消后台任务
         for task in self._tasks:
             task.cancel()
@@ -232,10 +243,6 @@ class RPCServer:
             payload=payload or {},
         )
 
-        # 背压检查
-        if self._send_queue and self._send_queue.full():
-            raise RPCError(ErrorCode.E_BACKPRESSURE, "发送队列已满")
-
         # 注册 pending future
         loop = asyncio.get_running_loop()
         future: asyncio.Future[Envelope] = loop.create_future()
@@ -244,7 +251,7 @@ class RPCServer:
         try:
             # 发送请求
             data = self._codec.encode_envelope(envelope)
-            await conn.send_frame(data)
+            await self._enqueue_send(conn, data)
 
             # 等待响应
             timeout_sec = timeout_ms / 1000.0
@@ -273,7 +280,7 @@ class RPCServer:
             payload=payload or {},
         )
         data = self._codec.encode_envelope(envelope)
-        await self._connection.send_frame(data)
+        await self._enqueue_send(self._connection, data)
 
     # ─── 内部方法 ──────────────────────────────────────────────
 
@@ -464,6 +471,59 @@ class RPCServer:
             else:
                 future.set_result(envelope)
 
+    async def _enqueue_send(self, conn: Connection, data: bytes) -> None:
+        """通过发送队列串行发送消息，提供真实背压。"""
+        if conn.is_closed:
+            raise RPCError(ErrorCode.E_PLUGIN_CRASHED, "Runner 未连接")
+
+        if self._send_queue is None:
+            await conn.send_frame(data)
+            return
+
+        loop = asyncio.get_running_loop()
+        send_future: asyncio.Future[None] = loop.create_future()
+
+        try:
+            self._send_queue.put_nowait((conn, data, send_future))
+        except asyncio.QueueFull:
+            raise RPCError(ErrorCode.E_BACKPRESSURE, "发送队列已满") from None
+
+        await send_future
+
+    async def _send_loop(self) -> None:
+        """后台发送循环：串行消费发送队列，统一执行连接写入。"""
+        if self._send_queue is None:
+            return
+
+        while True:
+            try:
+                conn, data, send_future = await self._send_queue.get()
+            except asyncio.CancelledError:
+                break
+
+            try:
+                if conn.is_closed:
+                    raise RPCError(ErrorCode.E_PLUGIN_CRASHED, "Runner 未连接")
+                await conn.send_frame(data)
+                if not send_future.done():
+                    send_future.set_result(None)
+            except asyncio.CancelledError:
+                if not send_future.done():
+                    send_future.set_exception(RPCError(ErrorCode.E_TIMEOUT, "服务器关闭"))
+                raise
+            except Exception as e:
+                send_error = e if isinstance(e, RPCError) else self._normalize_send_exception(e)
+                if not send_future.done():
+                    send_future.set_exception(send_error)
+            finally:
+                self._send_queue.task_done()
+
+    @staticmethod
+    def _normalize_send_exception(error: Exception) -> RPCError:
+        if isinstance(error, ConnectionError):
+            return RPCError(ErrorCode.E_PLUGIN_CRASHED, str(error))
+        return RPCError(ErrorCode.E_UNKNOWN, str(error))
+
     async def _handle_request(self, envelope: Envelope, conn: Connection) -> None:
         """处理来自 Runner 的请求（通常是能力调用 cap.*）"""
         handler = self._method_handlers.get(envelope.method)
@@ -530,3 +590,21 @@ class RPCServer:
                 stale_count += 1
             self._pending_requests.pop(request_id, None)
         return stale_count
+
+    def _fail_queued_sends(self, error_code: ErrorCode, message: str) -> int:
+        if self._send_queue is None:
+            return 0
+
+        failed_count = 0
+        while True:
+            try:
+                _conn, _data, send_future = self._send_queue.get_nowait()
+            except asyncio.QueueEmpty:
+                break
+
+            if not send_future.done():
+                send_future.set_exception(RPCError(error_code, message))
+                failed_count += 1
+            self._send_queue.task_done()
+
+        return failed_count