Initial Checks
Description
With stdio protocol, the lifespan runs on server start up as expected. However, with streamable-http the lifespan does not execute on server start up.
Example Code
from collections.abc import AsyncIterator
from contextlib import asynccontextmanager
from dataclasses import dataclass
from mcp.server.fastmcp import Context, FastMCP
from mcp.server.session import ServerSession
# Mock database class for example
class Database:
"""Mock database class for example."""
@classmethod
async def connect(cls) -> "Database":
"""Connect to database."""
return cls()
async def disconnect(self) -> None:
"""Disconnect from database."""
pass
def query(self) -> str:
"""Execute a query."""
return "Query result"
@dataclass
class AppContext:
"""Application context with typed dependencies."""
db: Database
@asynccontextmanager
async def app_lifespan(server: FastMCP) -> AsyncIterator[AppContext]:
"""Manage application lifecycle with type-safe context."""
# Initialize on startup
print("Enter lifespan")
db = await Database.connect()
try:
yield AppContext(db=db)
finally:
# Cleanup on shutdown
await db.disconnect()
# Pass lifespan to server
mcp = FastMCP("My App", lifespan=app_lifespan)
# Access type-safe lifespan context in tools
@mcp.tool()
def query_db(ctx: Context[ServerSession, AppContext]) -> str:
"""Tool that uses initialized resources."""
db = ctx.request_context.lifespan_context.db
return db.query()
mcp.run(transport="streamable-http") # on server startup, the lifespan does not runPython & MCP Python SDK
Initial Checks
Description
With
stdioprotocol, the lifespan runs on server start up as expected. However, withstreamable-httpthe lifespan does not execute on server start up.Example Code
Python & MCP Python SDK