🐛 优化MCPClient会话管理，添加会话过期清理机制和异常处理

nonebot_plugin_llmchat/mcpclient.py

@@ -1,5 +1,7 @@
 import asyncio
 from contextlib import AsyncExitStack
+from time import monotonic
+from typing import Any, cast
 
 from mcp import ClientSession, StdioServerParameters
 from mcp.client.sse import sse_client
@@ -13,6 +15,8 @@ from .onebottools import OneBotTools
 class MCPClient:
     _instance = None
     _initialized = False
+    _SESSION_TTL_SECONDS = 600
+    _SESSION_CLEANUP_INTERVAL_SECONDS = 60
 
     def __new__(cls, server_config: dict[str, MCPServerConfig] | None = None):
         if cls._instance is None:
@@ -30,6 +34,10 @@ class MCPClient:
         self.server_config = server_config
         self.sessions = {}
         self.exit_stack = AsyncExitStack()
+        self._session_exit_stacks: dict[str, AsyncExitStack] = {}
+        self._session_last_used: dict[str, float] = {}
+        self._session_lock = asyncio.Lock()
+        self._session_cleanup_task: asyncio.Task | None = None
         # 添加工具列表缓存
         self._tools_cache: list | None = None
         self._cache_initialized = False
@@ -55,80 +63,115 @@ class MCPClient:
         return cls._instance
 
     async def connect_to_servers(self):
+        await self._ensure_cleanup_task()
         logger.info(f"开始连接{len(self.server_config)}个MCP服务器")
-        for server_name, config in self.server_config.items():
+        for server_name in self.server_config:
             logger.debug(f"正在连接服务器[{server_name}]")
-            if config.url:
-                sse_transport = await self.exit_stack.enter_async_context(sse_client(url=config.url, headers=config.headers))
-                read, write = sse_transport
-                self.sessions[server_name] = await self.exit_stack.enter_async_context(ClientSession(read, write))
-                await self.sessions[server_name].initialize()
-            elif config.command:
-                stdio_transport = await self.exit_stack.enter_async_context(
-                    stdio_client(StdioServerParameters(**config.model_dump()))
-                )
-                read, write = stdio_transport
-                self.sessions[server_name] = await self.exit_stack.enter_async_context(ClientSession(read, write))
-                await self.sessions[server_name].initialize()
-            else:
-                raise ValueError("Server config must have either url or command")
-
+            await self._get_or_create_session(server_name)
             logger.info(f"已成功连接到MCP服务器[{server_name}]")
 
-    def _create_session_context(self, server_name: str):
-        """创建临时会话的异步上下文管理器"""
+    async def _create_server_session(self, server_name: str) -> tuple[ClientSession, AsyncExitStack]:
+        """创建并初始化一个新的服务器会话。"""
         config = self.server_config[server_name]
+        session_stack = AsyncExitStack()
+        if config.url:
+            transport = await session_stack.enter_async_context(
+                sse_client(url=config.url, headers=config.headers)
+            )
+        elif config.command:
+            transport = await session_stack.enter_async_context(
+                cast(Any, stdio_client(StdioServerParameters(**config.model_dump())))
+            )
+        else:
+            raise ValueError("Server config must have either url or command")
 
-        class SessionContext:
-            def __init__(self):
-                self.session = None
-                self.exit_stack = AsyncExitStack()
+        read, write = transport
+        session = await session_stack.enter_async_context(ClientSession(read, write))
+        await session.initialize()
+        return session, session_stack
 
-            async def __aenter__(self):
-                if config.url:
-                    transport = await self.exit_stack.enter_async_context(
-                        sse_client(url=config.url, headers=config.headers)
-                    )
-                elif config.command:
-                    transport = await self.exit_stack.enter_async_context(
-                        stdio_client(StdioServerParameters(**config.model_dump()))
-                    )
-                else:
-                    raise ValueError("Server config must have either url or command")
+    async def _close_server_session(self, server_name: str):
+        """关闭指定服务器会话。"""
+        session_stack = self._session_exit_stacks.pop(server_name, None)
+        self.sessions.pop(server_name, None)
+        self._session_last_used.pop(server_name, None)
 
-                read, write = transport
-                self.session = await self.exit_stack.enter_async_context(ClientSession(read, write))
-                await self.session.initialize()
-                return self.session
+        if session_stack is not None:
+            await session_stack.aclose()
 
-            async def __aexit__(self, exc_type, exc_val, exc_tb):
-                await self.exit_stack.aclose()
+    async def _get_or_create_session(self, server_name: str) -> ClientSession:
+        """获取可复用会话；若不存在或已过期则新建。"""
+        now = monotonic()
+        async with self._session_lock:
+            last_used = self._session_last_used.get(server_name)
+            session = self.sessions.get(server_name)
 
-        return SessionContext()
+            # 空闲超过阈值则销毁重建
+            if session is not None and last_used is not None:
+                if now - last_used > self._SESSION_TTL_SECONDS:
+                    logger.info(f"服务器[{server_name}]会话空闲超过10分钟，重新创建")
+                    await self._close_server_session(server_name)
+                    session = None
+
+            if session is None:
+                session, session_stack = await self._create_server_session(server_name)
+                self.sessions[server_name] = session
+                self._session_exit_stacks[server_name] = session_stack
+
+            self._session_last_used[server_name] = now
+            return self.sessions[server_name]
+
+    async def _cleanup_expired_sessions(self):
+        """回收空闲过期会话。"""
+        now = monotonic()
+        async with self._session_lock:
+            expired_servers = [
+                server_name
+                for server_name, last_used in self._session_last_used.items()
+                if now - last_used > self._SESSION_TTL_SECONDS
+            ]
+
+            for server_name in expired_servers:
+                logger.info(f"回收空闲MCP会话[{server_name}]")
+                await self._close_server_session(server_name)
+
+    async def _session_cleanup_loop(self):
+        try:
+            while True:
+                await asyncio.sleep(self._SESSION_CLEANUP_INTERVAL_SECONDS)
+                await self._cleanup_expired_sessions()
+        except asyncio.CancelledError:
+            logger.debug("MCP会话清理任务已取消")
+            raise
+
+    async def _ensure_cleanup_task(self):
+        if self._session_cleanup_task is None or self._session_cleanup_task.done():
+            self._session_cleanup_task = asyncio.create_task(self._session_cleanup_loop())
 
     async def init_tools_cache(self):
         """初始化工具列表缓存"""
         if not self._cache_initialized:
+            await self._ensure_cleanup_task()
             available_tools = []
             logger.info(f"初始化工具列表缓存，需要连接{len(self.server_config)}个服务器")
             for server_name in self.server_config.keys():
                 logger.debug(f"正在从服务器[{server_name}]获取工具列表")
-                async with self._create_session_context(server_name) as session:
-                    response = await session.list_tools()
-                    tools = response.tools
-                    logger.debug(f"在服务器[{server_name}]中找到{len(tools)}个工具")
+                session = await self._get_or_create_session(server_name)
+                response = await session.list_tools()
+                tools = response.tools
+                logger.debug(f"在服务器[{server_name}]中找到{len(tools)}个工具")
 
-                    available_tools.extend(
-                        {
-                            "type": "function",
-                            "function": {
-                                "name": f"mcp__{server_name}__{tool.name}",
-                                "description": tool.description,
-                                "parameters": tool.inputSchema,
-                            },
-                        }
-                        for tool in tools
-                    )
+                available_tools.extend(
+                    {
+                        "type": "function",
+                        "function": {
+                            "name": f"mcp__{server_name}__{tool.name}",
+                            "description": tool.description,
+                            "parameters": tool.inputSchema,
+                        },
+                    }
+                    for tool in tools
+                )
 
             # 缓存工具列表
             self._tools_cache = available_tools
@@ -149,7 +192,7 @@ class MCPClient:
         return available_tools
 
     async def call_tool(self, tool_name: str, tool_args: dict, group_id: int | None = None, bot_id: str | None = None):
-        """按需连接调用工具，调用后立即断开"""
+        """按需调用工具，MCP会话会在10分钟空闲后自动回收。"""
         # 检查是否是OneBot内置工具
         if tool_name.startswith("ob__"):
             if group_id is None or bot_id is None:
@@ -168,14 +211,20 @@ class MCPClient:
             real_tool_name = parts[2]
             logger.info(f"按需连接到服务器[{server_name}]调用工具[{real_tool_name}]")
 
-            async with self._create_session_context(server_name) as session:
-                try:
-                    response = await asyncio.wait_for(session.call_tool(real_tool_name, tool_args), timeout=30)
-                    logger.debug(f"工具[{real_tool_name}]调用完成，响应: {response}")
-                    return response.content
-                except asyncio.TimeoutError:
-                    logger.error(f"调用工具[{real_tool_name}]超时")
-                    return f"调用工具[{real_tool_name}]超时"
+            try:
+                await self._ensure_cleanup_task()
+                session = await self._get_or_create_session(server_name)
+                response = await asyncio.wait_for(session.call_tool(real_tool_name, tool_args), timeout=30)
+                logger.debug(f"工具[{real_tool_name}]调用完成，响应: {response}")
+                return response.content
+            except asyncio.TimeoutError:
+                logger.error(f"调用工具[{real_tool_name}]超时")
+                return f"调用工具[{real_tool_name}]超时"
+            except (RuntimeError, ValueError, TypeError, OSError, ConnectionError) as e:
+                logger.opt(exception=e).error(f"调用工具[{real_tool_name}]失败，准备重置会话")
+                async with self._session_lock:
+                    await self._close_server_session(server_name)
+                return f"调用工具[{real_tool_name}]失败: {e!s}"
 
         # 未知工具类型
         return f"未知的工具类型: {tool_name}"
@@ -211,6 +260,19 @@ class MCPClient:
         logger.debug("正在清理MCPClient资源")
         # 只清除缓存，不销毁单例
         # self.clear_tools_cache()  # 保留缓存，避免重复获取工具列表
+
+        if self._session_cleanup_task is not None:
+            self._session_cleanup_task.cancel()
+            try:
+                await self._session_cleanup_task
+            except asyncio.CancelledError:
+                pass
+            self._session_cleanup_task = None
+
+        async with self._session_lock:
+            for server_name in list(self.sessions.keys()):
+                await self._close_server_session(server_name)
+
         await self.exit_stack.aclose()
         # 重新初始化exit_stack以便后续使用
         self.exit_stack = AsyncExitStack()