Marcelo Trylesinski
58 lines
1.4 KiB
Python
58 lines
1.4 KiB
Python
"""Example showing lifespan support for startup/shutdown with strong typing."""
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from collections.abc import AsyncIterator
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from contextlib import asynccontextmanager
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from dataclasses import dataclass
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from mcp.server.fastmcp import Context, FastMCP
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from mcp.server.session import ServerSession
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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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return cls()
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async def disconnect(self) -> None:
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"""Disconnect from database."""
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pass
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def query(self) -> str:
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"""Execute a query."""
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return "Query result"
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@dataclass
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class AppContext:
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"""Application context with typed dependencies."""
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db: Database
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@asynccontextmanager
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async def app_lifespan(server: FastMCP) -> AsyncIterator[AppContext]:
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"""Manage application lifecycle with type-safe context."""
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# Initialize on startup
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db = await Database.connect()
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try:
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yield AppContext(db=db)
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finally:
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# Cleanup on shutdown
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await db.disconnect()
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# Pass lifespan to server
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mcp = FastMCP("My App", lifespan=app_lifespan)
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# Access type-safe lifespan context in tools
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@mcp.tool()
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def query_db(ctx: Context[ServerSession, AppContext]) -> str:
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"""Tool that uses initialized resources."""
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db = ctx.request_context.lifespan_context.db
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return db.query()
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