agent-framework/python/samples/02-agents/middleware/exception_handling_with_middleware.py

# Copyright (c) Microsoft. All rights reserved.

import asyncio
from collections.abc import Awaitable, Callable
from typing import Annotated

from agent_framework import Agent, FunctionInvocationContext, tool
from agent_framework.foundry import FoundryChatClient
from azure.identity.aio import AzureCliCredential
from dotenv import load_dotenv
from pydantic import Field

# Load environment variables from .env file
load_dotenv()

"""
Exception Handling with MiddlewareTypes

This sample demonstrates how to use middleware for centralized exception handling in function calls.
The example shows:

- How to catch exceptions thrown by functions and provide graceful error responses
- Overriding function results when errors occur to provide user-friendly messages
- Using middleware to implement retry logic, fallback mechanisms, or error reporting

The middleware catches TimeoutError from an unstable data service and replaces it with
a helpful message for the user, preventing raw exceptions from reaching the end user.
"""


# NOTE: approval_mode="never_require" is for sample brevity. Use "always_require" in production;
# see samples/02-agents/tools/function_tool_with_approval.py
# and samples/02-agents/tools/function_tool_with_approval_and_sessions.py.
@tool(approval_mode="never_require")
def unstable_data_service(
    query: Annotated[str, Field(description="The data query to execute.")],
) -> str:
    """A simulated data service that sometimes throws exceptions."""
    # Simulate failure
    raise TimeoutError("Data service request timed out")


async def exception_handling_middleware(
    context: FunctionInvocationContext, call_next: Callable[[], Awaitable[None]]
) -> None:
    function_name = context.function.name

    try:
        print(f"[ExceptionHandlingMiddleware] Executing function: {function_name}")
        await call_next()
        print(f"[ExceptionHandlingMiddleware] Function {function_name} completed successfully.")
    except TimeoutError as e:
        print(f"[ExceptionHandlingMiddleware] Caught TimeoutError: {e}")
        # Override function result to provide custom message in response.
        context.result = (
            "Request Timeout: The data service is taking longer than expected to respond."
            "Respond with message - 'Sorry for the inconvenience, please try again later.'"
        )


async def main() -> None:
    """Example demonstrating exception handling with middleware."""
    print("=== Exception Handling MiddlewareTypes Example ===")

    # For authentication, run `az login` command in terminal or replace AzureCliCredential with preferred
    # authentication option.
    async with (
        AzureCliCredential() as credential,
        Agent(
            client=FoundryChatClient(credential=credential),
            name="DataAgent",
            instructions="You are a helpful data assistant. Use the data service tool to fetch information for users.",
            tools=unstable_data_service,
            middleware=[exception_handling_middleware],
        ) as agent,
    ):
        query = "Get user statistics"
        print(f"User: {query}")
        result = await agent.run(query)
        print(f"Agent: {result}")


if __name__ == "__main__":
    asyncio.run(main())