mirror of
https://github.com/aljazceru/mcp-python-sdk.git
synced 2025-12-19 14:54:24 +01:00
StreamableHttp - Server transport with state management (#553)
This commit is contained in:
ihrpr
@@ -814,7 +814,10 @@ class Context(BaseModel, Generic[ServerSessionT, LifespanContextT]):
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**extra: Additional structured data to include
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"""
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await self.request_context.session.send_log_message(
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level=level, data=message, logger=logger_name
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level=level,
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data=message,
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logger=logger_name,
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related_request_id=self.request_id,
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)
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@property
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@@ -179,7 +179,11 @@ class ServerSession(
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)
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async def send_log_message(
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self, level: types.LoggingLevel, data: Any, logger: str | None = None
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self,
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level: types.LoggingLevel,
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data: Any,
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logger: str | None = None,
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related_request_id: types.RequestId | None = None,
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) -> None:
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"""Send a log message notification."""
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await self.send_notification(
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@@ -192,7 +196,8 @@ class ServerSession(
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logger=logger,
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),
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)
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)
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),
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related_request_id,
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)
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async def send_resource_updated(self, uri: AnyUrl) -> None:
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@@ -261,7 +266,11 @@ class ServerSession(
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)
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async def send_progress_notification(
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self, progress_token: str | int, progress: float, total: float | None = None
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self,
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progress_token: str | int,
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progress: float,
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total: float | None = None,
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related_request_id: str | None = None,
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) -> None:
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"""Send a progress notification."""
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await self.send_notification(
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@@ -274,7 +283,8 @@ class ServerSession(
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total=total,
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),
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)
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)
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),
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related_request_id,
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)
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async def send_resource_list_changed(self) -> None:
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644
src/mcp/server/streamableHttp.py
Normal file
644
src/mcp/server/streamableHttp.py
Normal file
@@ -0,0 +1,644 @@
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"""
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StreamableHTTP Server Transport Module
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This module implements an HTTP transport layer with Streamable HTTP.
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The transport handles bidirectional communication using HTTP requests and
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responses, with streaming support for long-running operations.
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"""
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import json
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import logging
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import re
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from collections.abc import AsyncGenerator
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from contextlib import asynccontextmanager
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from http import HTTPStatus
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from typing import Any
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import anyio
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from anyio.streams.memory import MemoryObjectReceiveStream, MemoryObjectSendStream
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from pydantic import ValidationError
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from sse_starlette import EventSourceResponse
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from starlette.requests import Request
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from starlette.responses import Response
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from starlette.types import Receive, Scope, Send
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from mcp.types import (
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INTERNAL_ERROR,
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INVALID_PARAMS,
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INVALID_REQUEST,
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PARSE_ERROR,
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ErrorData,
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JSONRPCError,
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JSONRPCMessage,
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JSONRPCNotification,
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JSONRPCRequest,
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JSONRPCResponse,
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RequestId,
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)
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logger = logging.getLogger(__name__)
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# Maximum size for incoming messages
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MAXIMUM_MESSAGE_SIZE = 4 * 1024 * 1024 # 4MB
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# Header names
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MCP_SESSION_ID_HEADER = "mcp-session-id"
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LAST_EVENT_ID_HEADER = "last-event-id"
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# Content types
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CONTENT_TYPE_JSON = "application/json"
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CONTENT_TYPE_SSE = "text/event-stream"
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# Session ID validation pattern (visible ASCII characters ranging from 0x21 to 0x7E)
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# Pattern ensures entire string contains only valid characters by using ^ and $ anchors
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SESSION_ID_PATTERN = re.compile(r"^[\x21-\x7E]+$")
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class StreamableHTTPServerTransport:
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"""
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HTTP server transport with event streaming support for MCP.
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Handles JSON-RPC messages in HTTP POST requests with SSE streaming.
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Supports optional JSON responses and session management.
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"""
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# Server notification streams for POST requests as well as standalone SSE stream
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_read_stream_writer: MemoryObjectSendStream[JSONRPCMessage | Exception] | None = (
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None
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)
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_write_stream_reader: MemoryObjectReceiveStream[JSONRPCMessage] | None = None
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def __init__(
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self,
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mcp_session_id: str | None,
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is_json_response_enabled: bool = False,
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) -> None:
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"""
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Initialize a new StreamableHTTP server transport.
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Args:
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mcp_session_id: Optional session identifier for this connection.
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Must contain only visible ASCII characters (0x21-0x7E).
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is_json_response_enabled: If True, return JSON responses for requests
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instead of SSE streams. Default is False.
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Raises:
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ValueError: If the session ID contains invalid characters.
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"""
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if mcp_session_id is not None and not SESSION_ID_PATTERN.fullmatch(
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mcp_session_id
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):
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raise ValueError(
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"Session ID must only contain visible ASCII characters (0x21-0x7E)"
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)
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self.mcp_session_id = mcp_session_id
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self.is_json_response_enabled = is_json_response_enabled
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self._request_streams: dict[
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RequestId, MemoryObjectSendStream[JSONRPCMessage]
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] = {}
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self._terminated = False
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def _create_error_response(
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self,
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error_message: str,
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status_code: HTTPStatus,
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error_code: int = INVALID_REQUEST,
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headers: dict[str, str] | None = None,
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) -> Response:
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"""Create an error response with a simple string message."""
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response_headers = {"Content-Type": CONTENT_TYPE_JSON}
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if headers:
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response_headers.update(headers)
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if self.mcp_session_id:
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response_headers[MCP_SESSION_ID_HEADER] = self.mcp_session_id
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# Return a properly formatted JSON error response
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error_response = JSONRPCError(
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jsonrpc="2.0",
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id="server-error", # We don't have a request ID for general errors
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error=ErrorData(
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code=error_code,
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message=error_message,
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),
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)
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return Response(
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error_response.model_dump_json(by_alias=True, exclude_none=True),
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status_code=status_code,
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headers=response_headers,
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)
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def _create_json_response(
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self,
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response_message: JSONRPCMessage | None,
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status_code: HTTPStatus = HTTPStatus.OK,
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headers: dict[str, str] | None = None,
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) -> Response:
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"""Create a JSON response from a JSONRPCMessage"""
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response_headers = {"Content-Type": CONTENT_TYPE_JSON}
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if headers:
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response_headers.update(headers)
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if self.mcp_session_id:
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response_headers[MCP_SESSION_ID_HEADER] = self.mcp_session_id
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return Response(
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response_message.model_dump_json(by_alias=True, exclude_none=True)
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if response_message
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else None,
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status_code=status_code,
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headers=response_headers,
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)
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def _get_session_id(self, request: Request) -> str | None:
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"""Extract the session ID from request headers."""
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return request.headers.get(MCP_SESSION_ID_HEADER)
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async def handle_request(self, scope: Scope, receive: Receive, send: Send) -> None:
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"""Application entry point that handles all HTTP requests"""
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request = Request(scope, receive)
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if self._terminated:
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# If the session has been terminated, return 404 Not Found
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response = self._create_error_response(
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"Not Found: Session has been terminated",
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HTTPStatus.NOT_FOUND,
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)
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await response(scope, receive, send)
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return
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if request.method == "POST":
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await self._handle_post_request(scope, request, receive, send)
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elif request.method == "GET":
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await self._handle_get_request(request, send)
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elif request.method == "DELETE":
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await self._handle_delete_request(request, send)
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else:
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await self._handle_unsupported_request(request, send)
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def _check_accept_headers(self, request: Request) -> tuple[bool, bool]:
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"""Check if the request accepts the required media types."""
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accept_header = request.headers.get("accept", "")
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accept_types = [media_type.strip() for media_type in accept_header.split(",")]
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has_json = any(
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media_type.startswith(CONTENT_TYPE_JSON) for media_type in accept_types
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)
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has_sse = any(
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media_type.startswith(CONTENT_TYPE_SSE) for media_type in accept_types
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)
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return has_json, has_sse
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def _check_content_type(self, request: Request) -> bool:
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"""Check if the request has the correct Content-Type."""
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content_type = request.headers.get("content-type", "")
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content_type_parts = [
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part.strip() for part in content_type.split(";")[0].split(",")
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]
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return any(part == CONTENT_TYPE_JSON for part in content_type_parts)
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async def _handle_post_request(
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self, scope: Scope, request: Request, receive: Receive, send: Send
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) -> None:
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"""Handle POST requests containing JSON-RPC messages."""
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writer = self._read_stream_writer
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if writer is None:
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raise ValueError(
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"No read stream writer available. Ensure connect() is called first."
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)
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try:
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# Check Accept headers
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has_json, has_sse = self._check_accept_headers(request)
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if not (has_json and has_sse):
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response = self._create_error_response(
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(
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"Not Acceptable: Client must accept both application/json and "
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"text/event-stream"
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),
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HTTPStatus.NOT_ACCEPTABLE,
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)
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await response(scope, receive, send)
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return
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# Validate Content-Type
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if not self._check_content_type(request):
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response = self._create_error_response(
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"Unsupported Media Type: Content-Type must be application/json",
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HTTPStatus.UNSUPPORTED_MEDIA_TYPE,
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)
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await response(scope, receive, send)
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return
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# Parse the body - only read it once
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body = await request.body()
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if len(body) > MAXIMUM_MESSAGE_SIZE:
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response = self._create_error_response(
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"Payload Too Large: Message exceeds maximum size",
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HTTPStatus.REQUEST_ENTITY_TOO_LARGE,
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)
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await response(scope, receive, send)
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return
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try:
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raw_message = json.loads(body)
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except json.JSONDecodeError as e:
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response = self._create_error_response(
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f"Parse error: {str(e)}", HTTPStatus.BAD_REQUEST, PARSE_ERROR
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)
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await response(scope, receive, send)
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return
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try:
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message = JSONRPCMessage.model_validate(raw_message)
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except ValidationError as e:
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response = self._create_error_response(
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f"Validation error: {str(e)}",
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HTTPStatus.BAD_REQUEST,
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INVALID_PARAMS,
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)
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await response(scope, receive, send)
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return
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# Check if this is an initialization request
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is_initialization_request = (
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isinstance(message.root, JSONRPCRequest)
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and message.root.method == "initialize"
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)
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if is_initialization_request:
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# Check if the server already has an established session
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if self.mcp_session_id:
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# Check if request has a session ID
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request_session_id = self._get_session_id(request)
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# If request has a session ID but doesn't match, return 404
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if request_session_id and request_session_id != self.mcp_session_id:
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response = self._create_error_response(
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"Not Found: Invalid or expired session ID",
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HTTPStatus.NOT_FOUND,
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)
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await response(scope, receive, send)
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return
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# For non-initialization requests, validate the session
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elif not await self._validate_session(request, send):
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return
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# For notifications and responses only, return 202 Accepted
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if not isinstance(message.root, JSONRPCRequest):
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# Create response object and send it
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response = self._create_json_response(
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None,
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HTTPStatus.ACCEPTED,
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)
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await response(scope, receive, send)
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# Process the message after sending the response
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await writer.send(message)
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return
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# Extract the request ID outside the try block for proper scope
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request_id = str(message.root.id)
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# Create promise stream for getting response
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request_stream_writer, request_stream_reader = (
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anyio.create_memory_object_stream[JSONRPCMessage](0)
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)
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# Register this stream for the request ID
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self._request_streams[request_id] = request_stream_writer
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if self.is_json_response_enabled:
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# Process the message
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await writer.send(message)
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try:
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# Process messages from the request-specific stream
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# We need to collect all messages until we get a response
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response_message = None
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# Use similar approach to SSE writer for consistency
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async for received_message in request_stream_reader:
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# If it's a response, this is what we're waiting for
|
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if isinstance(
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received_message.root, JSONRPCResponse | JSONRPCError
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):
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response_message = received_message
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break
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# For notifications and request, keep waiting
|
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else:
|
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logger.debug(f"received: {received_message.root.method}")
|
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|
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# At this point we should have a response
|
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if response_message:
|
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# Create JSON response
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response = self._create_json_response(response_message)
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await response(scope, receive, send)
|
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else:
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# This shouldn't happen in normal operation
|
||||
logger.error(
|
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"No response message received before stream closed"
|
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)
|
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response = self._create_error_response(
|
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"Error processing request: No response received",
|
||||
HTTPStatus.INTERNAL_SERVER_ERROR,
|
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)
|
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await response(scope, receive, send)
|
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except Exception as e:
|
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logger.exception(f"Error processing JSON response: {e}")
|
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response = self._create_error_response(
|
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f"Error processing request: {str(e)}",
|
||||
HTTPStatus.INTERNAL_SERVER_ERROR,
|
||||
INTERNAL_ERROR,
|
||||
)
|
||||
await response(scope, receive, send)
|
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finally:
|
||||
# Clean up the request stream
|
||||
if request_id in self._request_streams:
|
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self._request_streams.pop(request_id, None)
|
||||
await request_stream_reader.aclose()
|
||||
await request_stream_writer.aclose()
|
||||
else:
|
||||
# Create SSE stream
|
||||
sse_stream_writer, sse_stream_reader = (
|
||||
anyio.create_memory_object_stream[dict[str, Any]](0)
|
||||
)
|
||||
|
||||
async def sse_writer():
|
||||
# Get the request ID from the incoming request message
|
||||
try:
|
||||
async with sse_stream_writer, request_stream_reader:
|
||||
# Process messages from the request-specific stream
|
||||
async for received_message in request_stream_reader:
|
||||
# Build the event data
|
||||
event_data = {
|
||||
"event": "message",
|
||||
"data": received_message.model_dump_json(
|
||||
by_alias=True, exclude_none=True
|
||||
),
|
||||
}
|
||||
|
||||
await sse_stream_writer.send(event_data)
|
||||
|
||||
# If response, remove from pending streams and close
|
||||
if isinstance(
|
||||
received_message.root,
|
||||
JSONRPCResponse | JSONRPCError,
|
||||
):
|
||||
if request_id:
|
||||
self._request_streams.pop(request_id, None)
|
||||
break
|
||||
except Exception as e:
|
||||
logger.exception(f"Error in SSE writer: {e}")
|
||||
finally:
|
||||
logger.debug("Closing SSE writer")
|
||||
# Clean up the request-specific streams
|
||||
if request_id and request_id in self._request_streams:
|
||||
self._request_streams.pop(request_id, None)
|
||||
|
||||
# Create and start EventSourceResponse
|
||||
# SSE stream mode (original behavior)
|
||||
# Set up headers
|
||||
headers = {
|
||||
"Cache-Control": "no-cache, no-transform",
|
||||
"Connection": "keep-alive",
|
||||
"Content-Type": CONTENT_TYPE_SSE,
|
||||
**(
|
||||
{MCP_SESSION_ID_HEADER: self.mcp_session_id}
|
||||
if self.mcp_session_id
|
||||
else {}
|
||||
),
|
||||
}
|
||||
response = EventSourceResponse(
|
||||
content=sse_stream_reader,
|
||||
data_sender_callable=sse_writer,
|
||||
headers=headers,
|
||||
)
|
||||
|
||||
# Start the SSE response (this will send headers immediately)
|
||||
try:
|
||||
# First send the response to establish the SSE connection
|
||||
async with anyio.create_task_group() as tg:
|
||||
tg.start_soon(response, scope, receive, send)
|
||||
# Then send the message to be processed by the server
|
||||
await writer.send(message)
|
||||
except Exception:
|
||||
logger.exception("SSE response error")
|
||||
# Clean up the request stream if something goes wrong
|
||||
if request_id and request_id in self._request_streams:
|
||||
self._request_streams.pop(request_id, None)
|
||||
|
||||
except Exception as err:
|
||||
logger.exception("Error handling POST request")
|
||||
response = self._create_error_response(
|
||||
f"Error handling POST request: {err}",
|
||||
HTTPStatus.INTERNAL_SERVER_ERROR,
|
||||
INTERNAL_ERROR,
|
||||
)
|
||||
await response(scope, receive, send)
|
||||
if writer:
|
||||
await writer.send(err)
|
||||
return
|
||||
|
||||
async def _handle_get_request(self, request: Request, send: Send) -> None:
|
||||
"""Handle GET requests for SSE stream establishment."""
|
||||
# Validate session ID if server has one
|
||||
if not await self._validate_session(request, send):
|
||||
return
|
||||
# Validate Accept header - must include text/event-stream
|
||||
_, has_sse = self._check_accept_headers(request)
|
||||
|
||||
if not has_sse:
|
||||
response = self._create_error_response(
|
||||
"Not Acceptable: Client must accept text/event-stream",
|
||||
HTTPStatus.NOT_ACCEPTABLE,
|
||||
)
|
||||
await response(request.scope, request.receive, send)
|
||||
return
|
||||
|
||||
# TODO: Implement SSE stream for GET requests
|
||||
# For now, return 405 Method Not Allowed
|
||||
response = self._create_error_response(
|
||||
"SSE stream from GET request not implemented yet",
|
||||
HTTPStatus.METHOD_NOT_ALLOWED,
|
||||
)
|
||||
await response(request.scope, request.receive, send)
|
||||
|
||||
async def _handle_delete_request(self, request: Request, send: Send) -> None:
|
||||
"""Handle DELETE requests for explicit session termination."""
|
||||
# Validate session ID
|
||||
if not self.mcp_session_id:
|
||||
# If no session ID set, return Method Not Allowed
|
||||
response = self._create_error_response(
|
||||
"Method Not Allowed: Session termination not supported",
|
||||
HTTPStatus.METHOD_NOT_ALLOWED,
|
||||
)
|
||||
await response(request.scope, request.receive, send)
|
||||
return
|
||||
|
||||
if not await self._validate_session(request, send):
|
||||
return
|
||||
|
||||
self._terminate_session()
|
||||
|
||||
response = self._create_json_response(
|
||||
None,
|
||||
HTTPStatus.OK,
|
||||
)
|
||||
await response(request.scope, request.receive, send)
|
||||
|
||||
def _terminate_session(self) -> None:
|
||||
"""Terminate the current session, closing all streams.
|
||||
|
||||
Once terminated, all requests with this session ID will receive 404 Not Found.
|
||||
"""
|
||||
|
||||
self._terminated = True
|
||||
logger.info(f"Terminating session: {self.mcp_session_id}")
|
||||
|
||||
# We need a copy of the keys to avoid modification during iteration
|
||||
request_stream_keys = list(self._request_streams.keys())
|
||||
|
||||
# Close all request streams (synchronously)
|
||||
for key in request_stream_keys:
|
||||
try:
|
||||
# Get the stream
|
||||
stream = self._request_streams.get(key)
|
||||
if stream:
|
||||
# We must use close() here, not aclose() since this is a sync method
|
||||
stream.close()
|
||||
except Exception as e:
|
||||
logger.debug(f"Error closing stream {key} during termination: {e}")
|
||||
|
||||
# Clear the request streams dictionary immediately
|
||||
self._request_streams.clear()
|
||||
|
||||
async def _handle_unsupported_request(self, request: Request, send: Send) -> None:
|
||||
"""Handle unsupported HTTP methods."""
|
||||
headers = {
|
||||
"Content-Type": CONTENT_TYPE_JSON,
|
||||
"Allow": "GET, POST, DELETE",
|
||||
}
|
||||
if self.mcp_session_id:
|
||||
headers[MCP_SESSION_ID_HEADER] = self.mcp_session_id
|
||||
|
||||
response = self._create_error_response(
|
||||
"Method Not Allowed",
|
||||
HTTPStatus.METHOD_NOT_ALLOWED,
|
||||
headers=headers,
|
||||
)
|
||||
await response(request.scope, request.receive, send)
|
||||
|
||||
async def _validate_session(self, request: Request, send: Send) -> bool:
|
||||
"""Validate the session ID in the request."""
|
||||
if not self.mcp_session_id:
|
||||
# If we're not using session IDs, return True
|
||||
return True
|
||||
|
||||
# Get the session ID from the request headers
|
||||
request_session_id = self._get_session_id(request)
|
||||
|
||||
# If no session ID provided but required, return error
|
||||
if not request_session_id:
|
||||
response = self._create_error_response(
|
||||
"Bad Request: Missing session ID",
|
||||
HTTPStatus.BAD_REQUEST,
|
||||
)
|
||||
await response(request.scope, request.receive, send)
|
||||
return False
|
||||
|
||||
# If session ID doesn't match, return error
|
||||
if request_session_id != self.mcp_session_id:
|
||||
response = self._create_error_response(
|
||||
"Not Found: Invalid or expired session ID",
|
||||
HTTPStatus.NOT_FOUND,
|
||||
)
|
||||
await response(request.scope, request.receive, send)
|
||||
return False
|
||||
|
||||
return True
|
||||
|
||||
@asynccontextmanager
|
||||
async def connect(
|
||||
self,
|
||||
) -> AsyncGenerator[
|
||||
tuple[
|
||||
MemoryObjectReceiveStream[JSONRPCMessage | Exception],
|
||||
MemoryObjectSendStream[JSONRPCMessage],
|
||||
],
|
||||
None,
|
||||
]:
|
||||
"""Context manager that provides read and write streams for a connection.
|
||||
|
||||
Yields:
|
||||
Tuple of (read_stream, write_stream) for bidirectional communication
|
||||
"""
|
||||
|
||||
# Create the memory streams for this connection
|
||||
|
||||
read_stream_writer, read_stream = anyio.create_memory_object_stream[
|
||||
JSONRPCMessage | Exception
|
||||
](0)
|
||||
write_stream, write_stream_reader = anyio.create_memory_object_stream[
|
||||
JSONRPCMessage
|
||||
](0)
|
||||
|
||||
# Store the streams
|
||||
self._read_stream_writer = read_stream_writer
|
||||
self._write_stream_reader = write_stream_reader
|
||||
|
||||
# Start a task group for message routing
|
||||
async with anyio.create_task_group() as tg:
|
||||
# Create a message router that distributes messages to request streams
|
||||
async def message_router():
|
||||
try:
|
||||
async for message in write_stream_reader:
|
||||
# Determine which request stream(s) should receive this message
|
||||
target_request_id = None
|
||||
if isinstance(
|
||||
message.root, JSONRPCNotification | JSONRPCRequest
|
||||
):
|
||||
# Extract related_request_id from meta if it exists
|
||||
if (
|
||||
(params := getattr(message.root, "params", None))
|
||||
and (meta := params.get("_meta"))
|
||||
and (related_id := meta.get("related_request_id"))
|
||||
is not None
|
||||
):
|
||||
target_request_id = str(related_id)
|
||||
else:
|
||||
target_request_id = str(message.root.id)
|
||||
|
||||
# Send to the specific request stream if available
|
||||
if (
|
||||
target_request_id
|
||||
and target_request_id in self._request_streams
|
||||
):
|
||||
try:
|
||||
await self._request_streams[target_request_id].send(
|
||||
message
|
||||
)
|
||||
except (
|
||||
anyio.BrokenResourceError,
|
||||
anyio.ClosedResourceError,
|
||||
):
|
||||
# Stream might be closed, remove from registry
|
||||
self._request_streams.pop(target_request_id, None)
|
||||
except Exception as e:
|
||||
logger.exception(f"Error in message router: {e}")
|
||||
|
||||
# Start the message router
|
||||
tg.start_soon(message_router)
|
||||
|
||||
try:
|
||||
# Yield the streams for the caller to use
|
||||
yield read_stream, write_stream
|
||||
finally:
|
||||
for stream in list(self._request_streams.values()):
|
||||
try:
|
||||
await stream.aclose()
|
||||
except Exception:
|
||||
pass
|
||||
self._request_streams.clear()
|
||||
@@ -6,7 +6,6 @@ from types import TracebackType
|
||||
from typing import Any, Generic, TypeVar
|
||||
|
||||
import anyio
|
||||
import anyio.lowlevel
|
||||
import httpx
|
||||
from anyio.streams.memory import MemoryObjectReceiveStream, MemoryObjectSendStream
|
||||
from pydantic import BaseModel
|
||||
@@ -24,6 +23,7 @@ from mcp.types import (
|
||||
JSONRPCNotification,
|
||||
JSONRPCRequest,
|
||||
JSONRPCResponse,
|
||||
NotificationParams,
|
||||
RequestParams,
|
||||
ServerNotification,
|
||||
ServerRequest,
|
||||
@@ -274,16 +274,32 @@ class BaseSession(
|
||||
await response_stream.aclose()
|
||||
await response_stream_reader.aclose()
|
||||
|
||||
async def send_notification(self, notification: SendNotificationT) -> None:
|
||||
async def send_notification(
|
||||
self,
|
||||
notification: SendNotificationT,
|
||||
related_request_id: RequestId | None = None,
|
||||
) -> None:
|
||||
"""
|
||||
Emits a notification, which is a one-way message that does not expect
|
||||
a response.
|
||||
"""
|
||||
# Some transport implementations may need to set the related_request_id
|
||||
# to attribute to the notifications to the request that triggered them.
|
||||
if related_request_id is not None and notification.root.params is not None:
|
||||
# Create meta if it doesn't exist
|
||||
if notification.root.params.meta is None:
|
||||
meta_dict = {"related_request_id": related_request_id}
|
||||
|
||||
else:
|
||||
meta_dict = notification.root.params.meta.model_dump(
|
||||
by_alias=True, mode="json", exclude_none=True
|
||||
)
|
||||
meta_dict["related_request_id"] = related_request_id
|
||||
notification.root.params.meta = NotificationParams.Meta(**meta_dict)
|
||||
jsonrpc_notification = JSONRPCNotification(
|
||||
jsonrpc="2.0",
|
||||
**notification.model_dump(by_alias=True, mode="json", exclude_none=True),
|
||||
)
|
||||
|
||||
await self._write_stream.send(JSONRPCMessage(jsonrpc_notification))
|
||||
|
||||
async def _send_response(
|
||||
|
||||
Reference in New Issue
Block a user