from __future__ import annotations import enum import typing from contextlib import AsyncExitStack import traceback from langbot_plugin.api.entities.events import pipeline_query import sqlalchemy import asyncio import httpx import uuid as uuid_module from mcp import ClientSession, StdioServerParameters from mcp.client.stdio import stdio_client from mcp.client.sse import sse_client from mcp.client.streamable_http import streamable_http_client from .. import loader from ....core import app import langbot_plugin.api.entities.builtin.resource.tool as resource_tool import langbot_plugin.api.entities.builtin.provider.message as provider_message from ....entity.persistence import mcp as persistence_mcp from .mcp_stdio import BoxStdioSessionRuntime, MCPServerBoxConfig, MCPSessionErrorPhase # noqa: F401 class MCPSessionStatus(enum.Enum): CONNECTING = 'connecting' CONNECTED = 'connected' ERROR = 'error' class RuntimeMCPSession: """运行时 MCP 会话""" ap: app.Application server_name: str server_uuid: str server_config: dict session: ClientSession | None exit_stack: AsyncExitStack functions: list[resource_tool.LLMTool] = [] enable: bool # connected: bool status: MCPSessionStatus _lifecycle_task: asyncio.Task | None _shutdown_event: asyncio.Event _ready_event: asyncio.Event error_message: str | None = None error_phase: MCPSessionErrorPhase | None = None retry_count: int = 0 _box_stdio_runtime: BoxStdioSessionRuntime def __init__(self, server_name: str, server_config: dict, enable: bool, ap: app.Application): self.server_name = server_name self.server_uuid = server_config.get('uuid', '') self.server_config = server_config self.ap = ap self.enable = enable self.session = None # Transient test sessions (created from the config page "test" button, # which carry no persisted server UUID) must NOT share the live # "mcp-shared" Box session. Otherwise a failing test churns the shared # session and tears down healthy, already-connected servers. Callers # flag these via server_config['_transient'] = True. self.is_transient = bool(server_config.get('_transient', False)) self.exit_stack = AsyncExitStack() self.functions = [] self.status = MCPSessionStatus.CONNECTING self._lifecycle_task = None self._shutdown_event = asyncio.Event() self._ready_event = asyncio.Event() self._box_stdio_runtime = BoxStdioSessionRuntime(self) self.box_config = self._box_stdio_runtime.config async def _init_stdio_python_server(self): if self._uses_box_stdio(): await self._box_stdio_runtime.initialize() return # Box is configured (ap.box_service exists) but currently unavailable # (disabled by config or connection failed). Refuse stdio MCP rather # than silently falling through to host-stdio — the operator asked # for the sandbox and the failure mode should be visible. # # Set ``error_phase = BOX_UNAVAILABLE`` BEFORE raising so the retry # wrapper can short-circuit (retrying is pointless when Box is # deliberately off) and the frontend can render a localized, # actionable message instead of this raw RuntimeError. Keep the # message itself short — the frontend ignores it for this phase. box_service = getattr(self.ap, 'box_service', None) if box_service is not None and not getattr(box_service, 'available', False): self.error_phase = MCPSessionErrorPhase.BOX_UNAVAILABLE if not getattr(box_service, 'enabled', True): raise RuntimeError('box_disabled_in_config') raise RuntimeError('box_unavailable') # Legacy: no box_service installed at all (pre-Box dev mode). Fall # through to host-stdio for backward compatibility. server_params = StdioServerParameters( command=self.server_config['command'], args=self.server_config['args'], env=self.server_config['env'], ) stdio_transport = await self.exit_stack.enter_async_context(stdio_client(server_params)) stdio, write = stdio_transport self.session = await self.exit_stack.enter_async_context(ClientSession(stdio, write)) await self.session.initialize() async def _init_box_stdio_server(self): await self._box_stdio_runtime.initialize() async def _init_sse_server(self): sse_transport = await self.exit_stack.enter_async_context( sse_client( self.server_config['url'], headers=self.server_config.get('headers', {}), timeout=self.server_config.get('timeout', 10), sse_read_timeout=self.server_config.get('ssereadtimeout', 30), ) ) sseio, write = sse_transport self.session = await self.exit_stack.enter_async_context(ClientSession(sseio, write)) await self.session.initialize() async def _init_streamable_http_server(self): transport = await self.exit_stack.enter_async_context( streamable_http_client( self.server_config['url'], http_client=httpx.AsyncClient( headers=self.server_config.get('headers', {}), timeout=self.server_config.get('timeout', 10), follow_redirects=True, ), ) ) read, write, _ = transport self.session = await self.exit_stack.enter_async_context(ClientSession(read, write)) await self.session.initialize() _MAX_RETRIES = 3 _RETRY_DELAYS = [2, 4, 8] async def _lifecycle_loop(self): """Manage the full MCP session lifecycle in a background task.""" try: if self.server_config['mode'] == 'stdio': await self._init_stdio_python_server() elif self.server_config['mode'] == 'sse': await self._init_sse_server() elif self.server_config['mode'] == 'http': await self._init_streamable_http_server() else: raise ValueError(f'Unknown MCP server mode: {self.server_name}: {self.server_config}') await self.refresh() self.status = MCPSessionStatus.CONNECTED # Notify start() that connection is established self._ready_event.set() # Wait for shutdown signal, with optional health monitoring for Box stdio if self._uses_box_stdio(): monitor_task = asyncio.create_task(self._box_stdio_runtime.monitor_process_health()) shutdown_task = asyncio.create_task(self._shutdown_event.wait()) done, pending = await asyncio.wait( [shutdown_task, monitor_task], return_when=asyncio.FIRST_COMPLETED, ) for task in pending: task.cancel() for task in done: if task is monitor_task and not self._shutdown_event.is_set(): self.error_phase = MCPSessionErrorPhase.RUNTIME raise Exception('Box managed process exited unexpectedly') else: await self._shutdown_event.wait() except Exception as e: self.status = MCPSessionStatus.ERROR self.error_message = str(e) self.ap.logger.error(f'Error in MCP session lifecycle {self.server_name}: {e}\n{traceback.format_exc()}') # Do NOT set _ready_event here — let _lifecycle_loop_with_retry # handle retries first. It will set the event when all retries # are exhausted or on success. raise # Re-raise so _lifecycle_loop_with_retry can catch it finally: # Clean up all resources in the same task try: if self.exit_stack: await self.exit_stack.aclose() self.exit_stack = AsyncExitStack() self.functions.clear() self.session = None except Exception as e: self.ap.logger.error(f'Error cleaning up MCP session {self.server_name}: {e}\n{traceback.format_exc()}') finally: await self._cleanup_box_stdio_session() async def _lifecycle_loop_with_retry(self): """Wrap _lifecycle_loop with retry and exponential backoff.""" for attempt in range(self._MAX_RETRIES + 1): try: await self._lifecycle_loop() return # Normal shutdown, don't retry except Exception as e: self.retry_count = attempt + 1 if self._shutdown_event.is_set(): return # Shutdown requested, don't retry # BOX_UNAVAILABLE is a deliberate refusal, not a transient # failure — retrying produces log spam and a misleading # "Failed after N attempts" message. Surface it immediately. if self.error_phase == MCPSessionErrorPhase.BOX_UNAVAILABLE: self.status = MCPSessionStatus.ERROR self.error_message = str(e) self._ready_event.set() return if attempt >= self._MAX_RETRIES: self.status = MCPSessionStatus.ERROR self.error_message = f'Failed after {self._MAX_RETRIES + 1} attempts: {self._describe_exception(e)}' self._ready_event.set() return delay = self._RETRY_DELAYS[attempt] self.ap.logger.warning( f'MCP session {self.server_name} failed (attempt {attempt + 1}), ' f'retrying in {delay}s: {self._describe_exception(e)}' ) await self._cleanup_box_stdio_session() # Reset status for retry self.status = MCPSessionStatus.CONNECTING self.error_message = None self.error_phase = None await asyncio.sleep(delay) @staticmethod def _describe_exception(exc: BaseException) -> str: """Flatten an exception into its underlying leaf messages. anyio / the MCP client wrap real failures in a TaskGroup, whose own message is the unhelpful "unhandled errors in a TaskGroup (N sub-exception)". Recurse into ExceptionGroups so the actual cause (e.g. ``httpx.HTTPStatusError: Client error '410 Gone'``) is surfaced. """ leaves: list[str] = [] def visit(e: BaseException) -> None: sub = getattr(e, 'exceptions', None) if sub: # ExceptionGroup / BaseExceptionGroup for child in sub: visit(child) else: leaves.append(f'{type(e).__name__}: {e}') visit(exc) seen: set[str] = set() unique = [m for m in leaves if not (m in seen or seen.add(m))] return '; '.join(unique) if unique else f'{type(exc).__name__}: {exc}' _MONITOR_POLL_INTERVAL = 5 _MONITOR_MAX_CONSECUTIVE_ERRORS = 3 async def _monitor_box_process_health(self): await self._box_stdio_runtime.monitor_process_health() async def start(self): if not self.enable: return # Create background task for lifecycle management with retry self._lifecycle_task = asyncio.create_task(self._lifecycle_loop_with_retry()) # Wait for connection or failure (with timeout) startup_timeout = (self.box_config.startup_timeout_sec + 30) if self._uses_box_stdio() else 30.0 try: await asyncio.wait_for(self._ready_event.wait(), timeout=startup_timeout) except asyncio.TimeoutError: self.status = MCPSessionStatus.ERROR raise Exception(f'Connection timeout after {startup_timeout} seconds') # Check for errors if self.status == MCPSessionStatus.ERROR: raise Exception('Connection failed, please check URL') async def refresh(self): if not self.session: return self.functions.clear() tools = await self.session.list_tools() self.ap.logger.debug(f'Refresh MCP tools: {tools}') for tool in tools.tools: async def func(*, _tool=tool, **kwargs): if not self.session: raise Exception('MCP session is not connected') result = await self.session.call_tool(_tool.name, kwargs) if result.isError: error_texts = [] for content in result.content: if content.type == 'text': error_texts.append(content.text) raise Exception('\n'.join(error_texts) if error_texts else 'Unknown error from MCP tool') result_contents: list[provider_message.ContentElement] = [] for content in result.content: if content.type == 'text': result_contents.append(provider_message.ContentElement.from_text(content.text)) elif content.type == 'image': result_contents.append(provider_message.ContentElement.from_image_base64(content.image_base64)) elif content.type == 'resource': # TODO: Handle resource content pass return result_contents func.__name__ = tool.name self.functions.append( resource_tool.LLMTool( name=tool.name, human_desc=tool.description or '', description=tool.description or '', parameters=tool.inputSchema, func=func, ) ) def get_tools(self) -> list[resource_tool.LLMTool]: return self.functions def get_runtime_info_dict(self) -> dict: info = { 'status': self.status.value, 'error_message': self.error_message, 'error_phase': self.error_phase.value if self.error_phase else None, 'retry_count': self.retry_count, 'tool_count': len(self.get_tools()), 'tools': [ { 'name': tool.name, 'description': tool.description, 'parameters': tool.parameters, } for tool in self.get_tools() ], } if self._uses_box_stdio(): info['box_session_id'] = self._build_box_session_id() info['box_enabled'] = True return info async def shutdown(self): """关闭会话并清理资源""" try: # 设置shutdown事件，通知lifecycle任务退出 self._shutdown_event.set() # 等待lifecycle任务完成（带超时） if self._lifecycle_task and not self._lifecycle_task.done(): try: await asyncio.wait_for(self._lifecycle_task, timeout=5.0) except asyncio.TimeoutError: self.ap.logger.warning(f'MCP session {self.server_name} shutdown timeout, cancelling task') self._lifecycle_task.cancel() try: await self._lifecycle_task except asyncio.CancelledError: pass self.ap.logger.info(f'MCP session {self.server_name} shutdown complete') except Exception as e: self.ap.logger.error(f'Error shutting down MCP session {self.server_name}: {e}\n{traceback.format_exc()}') def _uses_box_stdio(self) -> bool: return self._box_stdio_runtime.uses_box_stdio() def _build_box_session_id(self) -> str: # Transient test sessions get their own isolated Box session so a # failing/short-lived test can never disturb the shared session that # hosts live, already-connected MCP servers. if self.is_transient: return f'mcp-test-{self.server_uuid}' return 'mcp-shared' def _rewrite_path(self, path: str, host_path: str | None) -> str: return self._box_stdio_runtime.rewrite_path(path, host_path) def _infer_host_path(self) -> str | None: return self._box_stdio_runtime.infer_host_path() @staticmethod def _unwrap_venv_path(directory: str) -> str: return BoxStdioSessionRuntime.unwrap_venv_path(directory) def _resolve_host_path(self) -> str | None: return self._box_stdio_runtime.resolve_host_path() @staticmethod def _detect_install_command(host_path: str) -> str | None: return BoxStdioSessionRuntime.detect_install_command(host_path) def _build_box_session_payload(self, session_id: str, host_path: str | None = None) -> dict: return self._box_stdio_runtime.build_box_session_payload(session_id, host_path) def _build_box_process_payload(self, host_path: str | None = None) -> dict: return self._box_stdio_runtime.build_box_process_payload(host_path) def _rewrite_venv_command(self, command: str, host_path: str) -> str: return self._box_stdio_runtime.rewrite_venv_command(command, host_path) async def _cleanup_box_stdio_session(self) -> None: await self._box_stdio_runtime.cleanup_session() # @loader.loader_class('mcp') class MCPLoader(loader.ToolLoader): """MCP 工具加载器。 在此加载器中管理所有与 MCP Server 的连接。 """ sessions: dict[str, RuntimeMCPSession] _last_listed_functions: list[resource_tool.LLMTool] _hosted_mcp_tasks: list[asyncio.Task] def __init__(self, ap: app.Application): super().__init__(ap) self.sessions = {} self._last_listed_functions = [] self._hosted_mcp_tasks = [] async def initialize(self): await self.load_mcp_servers_from_db() async def load_mcp_servers_from_db(self): self.ap.logger.info('Loading MCP servers from db...') self.sessions = {} result = await self.ap.persistence_mgr.execute_async(sqlalchemy.select(persistence_mcp.MCPServer)) servers = result.all() for server in servers: config = self.ap.persistence_mgr.serialize_model(persistence_mcp.MCPServer, server) task = asyncio.create_task(self.host_mcp_server(config)) self._hosted_mcp_tasks.append(task) async def host_mcp_server(self, server_config: dict): self.ap.logger.debug(f'Loading MCP server {server_config}') try: session = await self.load_mcp_server(server_config) self.sessions[server_config['name']] = session except Exception as e: self.ap.logger.error( f'Failed to load MCP server from db: {server_config["name"]}({server_config["uuid"]}): {e}\n{traceback.format_exc()}' ) return self.ap.logger.debug(f'Starting MCP server {server_config["name"]}({server_config["uuid"]})') try: await session.start() except Exception as e: self.ap.logger.error( f'Failed to start MCP server {server_config["name"]}({server_config["uuid"]}): {e}\n{traceback.format_exc()}' ) return self.ap.logger.debug(f'Started MCP server {server_config["name"]}({server_config["uuid"]})') async def load_mcp_server(self, server_config: dict) -> RuntimeMCPSession: """加载 MCP 服务器到运行时 Args: server_config: 服务器配置字典，必须包含: - name: 服务器名称 - mode: 连接模式 (stdio/sse/http) - enable: 是否启用 - extra_args: 额外的配置参数 (可选) """ uuid_ = server_config.get('uuid') is_transient = False if not uuid_: self.ap.logger.warning('Server UUID is None for MCP server, maybe testing in the config page.') uuid_ = str(uuid_module.uuid4()) server_config['uuid'] = uuid_ # No persisted UUID => this is a throwaway "test" session from the # config page. Isolate it from the shared live Box session. is_transient = True name = server_config['name'] uuid = server_config['uuid'] mode = server_config['mode'] enable = server_config['enable'] extra_args = server_config.get('extra_args', {}) mixed_config = { 'name': name, 'uuid': uuid, 'mode': mode, 'enable': enable, '_transient': is_transient, **extra_args, } session = RuntimeMCPSession(name, mixed_config, enable, self.ap) return session async def get_tools(self, bound_mcp_servers: list[str] | None = None) -> list[resource_tool.LLMTool]: all_functions = [] for session in self.sessions.values(): # If bound_mcp_servers is specified, only include tools from those servers if bound_mcp_servers is not None: if session.server_uuid in bound_mcp_servers: all_functions.extend(session.get_tools()) else: # If no bound servers specified, include all tools all_functions.extend(session.get_tools()) self._last_listed_functions = all_functions return all_functions async def has_tool(self, name: str) -> bool: """检查工具是否存在""" for session in self.sessions.values(): for function in session.get_tools(): if function.name == name: return True return False async def invoke_tool(self, name: str, parameters: dict, query: pipeline_query.Query) -> typing.Any: """执行工具调用""" for session in self.sessions.values(): for function in session.get_tools(): if function.name == name: self.ap.logger.debug(f'Invoking MCP tool: {name} with parameters: {parameters}') try: result = await function.func(**parameters) self.ap.logger.debug(f'MCP tool {name} executed successfully') return result except Exception as e: self.ap.logger.error(f'Error invoking MCP tool {name}: {e}\n{traceback.format_exc()}') raise raise ValueError(f'Tool not found: {name}') async def remove_mcp_server(self, server_name: str): """移除 MCP 服务器""" if server_name not in self.sessions: self.ap.logger.warning(f'MCP server {server_name} not found in sessions, skipping removal') return session = self.sessions.pop(server_name) await session.shutdown() self.ap.logger.info(f'Removed MCP server: {server_name}') def get_session(self, server_name: str) -> RuntimeMCPSession | None: """获取指定名称的 MCP 会话""" return self.sessions.get(server_name) def has_session(self, server_name: str) -> bool: """检查是否存在指定名称的 MCP 会话""" return server_name in self.sessions def get_all_server_names(self) -> list[str]: """获取所有已加载的 MCP 服务器名称""" return list(self.sessions.keys()) def get_server_tool_count(self, server_name: str) -> int: """获取指定服务器的工具数量""" session = self.get_session(server_name) return len(session.get_tools()) if session else 0 def get_all_servers_info(self) -> dict[str, dict]: """获取所有服务器的信息""" info = {} for server_name, session in self.sessions.items(): tools = session.get_tools() info[server_name] = { 'name': server_name, 'mode': session.server_config.get('mode'), 'enable': session.enable, 'tools_count': len(tools), 'tool_names': [f.name for f in tools], } return info async def shutdown(self): """关闭所有工具""" self.ap.logger.info('Shutting down all MCP sessions...') for server_name, session in list(self.sessions.items()): try: await session.shutdown() self.ap.logger.debug(f'Shutdown MCP session: {server_name}') except Exception as e: self.ap.logger.error(f'Error shutting down MCP session {server_name}: {e}\n{traceback.format_exc()}') self.sessions.clear() self.ap.logger.info('All MCP sessions shutdown complete')