Using get_fast_api_app to run my agents here it throws ERROR:asyncio:Unclosed client session client_session: <aiohttp.client.ClientSession object at 0x16b6d1d30> ERROR:asyncio:Unclosed client session client_session: <aiohttp.client.ClientSession object at 0x16b51bf50>

[pavan-moe]

Using get_fast_api_app to run my agents here it throws ERROR:asyncio:Unclosed client session client_session: <aiohttp.client.ClientSession object at 0x16b6d1d30> ERROR:asyncio:Unclosed client session client_session: <aiohttp.client.ClientSession object at 0x16b51bf50>

While the same code works perfectly with ADK Web, it throws errors when using get_fast_api_app, causing the agent execution to stop unexpectedly. Is there a workaround for this? This is happening so frequently, like more than 80% of the time, and I am using the MCP toolset with SSE.

[adk-bot]

Response from ADK Answering Agent (experimental, answer may be inaccurate)

TLDR: The ERROR:asyncio:Unclosed client session error you are encountering is likely due to the aiohttp.ClientSession within the McpToolset not being properly closed on application shutdown. You can resolve this by creating an instance of your McpToolset in the global scope and using FastAPI's shutdown event to call its close() method, ensuring all resources are gracefully released.

---

Hello! Thank you for your question.

The ERROR:asyncio:Unclosed client session error typically occurs in asyncio applications when an aiohttp.ClientSession is not closed before the program exits.

The McpToolset, which you are using, utilizes aiohttp for Server-Sent Events (SSE) connections. [1] When your FastAPI application, created with get_fast_api_app, shuts down, these sessions need to be explicitly closed to prevent this error.

While adk web handles this lifecycle for you, when using get_fast_api_app for a custom deployment, you need to manage the cleanup of resources like the McpToolset yourself.

You can achieve this by creating an instance of your McpToolset and registering its close method to be called during FastAPI's shutdown event.

Here is an example of how you can modify your main application file:

import asyncio
from fastapi import FastAPI
from google.adk.cli.fast_api import get_fast_api_app
from google.adk.tools.mcp_tool import McpToolset, SseConnectionParams

# 1. Create your McpToolset instance
# Replace with your actual connection parameters
mcp_toolset = McpToolset(
    connection_params=SseConnectionParams(
        url="http://localhost:8080/mcp",
        # Add other necessary parameters here
    )
)

# 2. Get the FastAPI app from ADK
# Make sure your agent is configured to use the 'mcp_toolset' instance
app: FastAPI = get_fast_api_app(
    agents_dir="./agents",
    # ... other parameters
)

# 3. Add a shutdown event handler to close the toolset
@app.on_event("shutdown")
async def shutdown_event():
    print("Shutting down and closing MCP toolset...")
    await mcp_toolset.close()
    print("MCP toolset closed.")

# In your agent definition, you would pass the created toolset:
#
# from my_app import mcp_toolset
#
# root_agent = Agent(
#     ...,
#     tools=[mcp_toolset]
# )

By implementing this shutdown hook, you ensure that the McpToolset has a chance to clean up its aiohttp client sessions, which should resolve the "Unclosed client session" errors.

Let me know if you have any other questions!

---

[1] gs://adk-knowledge-bucket-cloud-vi-test/adk-python/src/google/adk/tools/mcp_tool/mcp_session_manager.py

[pavan-moe]

ERROR:asyncio:Unclosed client session
client_session: <aiohttp.client.ClientSession object at 0x10e515ca0>

still the same

import uvicorn
from google.adk.cli.fast_api import get_fast_api_app
from google.adk.tools.mcp_tool import McpToolset, SseConnectionParams
from contextlib import asynccontextmanager
from fastapi import FastAPI
from config import config
from config import mcp_toolset

agent_config = config.get_agent_config()

async def startup_event():
print("starting app")

async def shutdown_event():
print("Shutting down and closing MCP toolset...")
await mcp_toolset.close()
print("MCP toolset closed.")

@asynccontextmanager
async def lifespan(app: FastAPI):
# Store the app instance for potential use in startup/shutdown
app.state.mcp_toolset = mcp_toolset
await startup_event()
yield
await shutdown_event()

app:FastAPI = get_fast_api_app(
agents_dir=agent_config["agents_dir"],
session_service_uri=agent_config["session_service_uri"],
allow_origins=["*"],
web=False,
lifespan=lifespan
)

if name == "main":
print(f"Starting server on {config.host}:{config.port}")
print("Press Ctrl+C to stop the server")

uvicorn.run(
    app=app,
    host=config.host,
    port=config.port,
    log_level=config.log_level.lower(),
    access_log=True,
    use_colors=True,
)

[pavan-moe]

i have commented out MCP related stuff and still it is throwing the same error.