104 lines
2.8 KiB
Python
104 lines
2.8 KiB
Python
"""
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Run from the repository root:
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uv run examples/snippets/servers/lowlevel/lifespan.py
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"""
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from collections.abc import AsyncIterator
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from contextlib import asynccontextmanager
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from typing import Any
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import mcp.server.stdio
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import mcp.types as types
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from mcp.server.lowlevel import NotificationOptions, Server
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from mcp.server.models import InitializationOptions
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# Mock database class for example
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class Database:
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"""Mock database class for example."""
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@classmethod
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async def connect(cls) -> "Database":
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"""Connect to database."""
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print("Database connected")
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return cls()
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async def disconnect(self) -> None:
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"""Disconnect from database."""
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print("Database disconnected")
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async def query(self, query_str: str) -> list[dict[str, str]]:
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"""Execute a query."""
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# Simulate database query
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return [{"id": "1", "name": "Example", "query": query_str}]
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@asynccontextmanager
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async def server_lifespan(_server: Server) -> AsyncIterator[dict[str, Any]]:
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"""Manage server startup and shutdown lifecycle."""
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# Initialize resources on startup
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db = await Database.connect()
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try:
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yield {"db": db}
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finally:
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# Clean up on shutdown
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await db.disconnect()
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# Pass lifespan to server
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server = Server("example-server", lifespan=server_lifespan)
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@server.list_tools()
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async def handle_list_tools() -> list[types.Tool]:
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"""List available tools."""
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return [
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types.Tool(
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name="query_db",
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description="Query the database",
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input_schema={
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"type": "object",
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"properties": {"query": {"type": "string", "description": "SQL query to execute"}},
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"required": ["query"],
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},
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)
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]
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@server.call_tool()
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async def query_db(name: str, arguments: dict[str, Any]) -> list[types.TextContent]:
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"""Handle database query tool call."""
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if name != "query_db":
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raise ValueError(f"Unknown tool: {name}")
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# Access lifespan context
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ctx = server.request_context
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db = ctx.lifespan_context["db"]
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# Execute query
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results = await db.query(arguments["query"])
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return [types.TextContent(type="text", text=f"Query results: {results}")]
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async def run():
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"""Run the server with lifespan management."""
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async with mcp.server.stdio.stdio_server() as (read_stream, write_stream):
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await server.run(
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read_stream,
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write_stream,
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InitializationOptions(
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server_name="example-server",
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server_version="0.1.0",
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capabilities=server.get_capabilities(
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notification_options=NotificationOptions(),
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experimental_capabilities={},
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),
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),
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)
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if __name__ == "__main__":
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import asyncio
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asyncio.run(run())
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