Server Lifespan
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Defining a Lifespan
The lifespan is an async generator function decorated with @lifespan. It yields once, and whatever you yield becomes available to all tools via ctx.lifespan_context. The try/finally block ensures cleanup code runs even if the server is cancelled or an exception occurs:
from fastmcp import FastMCP, Context
from fastmcp.server.lifespan import lifespan
@lifespan
async def app_lifespan(server):
# This runs once when the server starts
db = await connect_to_database()
try:
yield {"db": db} # make db available to all tools
finally:
# This runs once when the server stops
await db.close()
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