deer-flow/server.py

# Copyright (c) 2025 Bytedance Ltd. and/or its affiliates
# SPDX-License-Identifier: MIT

"""
Server script for running the DeerFlow API.
"""

import argparse
import asyncio
import logging
import os
import signal
import sys

import uvicorn

# Configure logging
logging.basicConfig(
    level=logging.INFO,
    format="%(asctime)s - %(name)s - %(levelname)s - %(message)s",
)

logger = logging.getLogger(__name__)

# To ensure compatibility with Windows event loop issues when using Uvicorn and Asyncio Checkpointer,
# This is necessary because some libraries expect a selector-based event loop.
# This is a workaround for issues with Uvicorn and Watchdog on Windows.
# See:
# Since Python 3.8 the default on Windows is the Proactor event loop,
# which lacks add_reader/add_writer and can break libraries that expect selector-based I/O (e.g., some Uvicorn/Watchdog/stdio integrations).
# For compatibility, this forces the selector loop.
if os.name == "nt":
    logger.info("Setting Windows event loop policy for asyncio")
    asyncio.set_event_loop_policy(asyncio.WindowsSelectorEventLoopPolicy())


def handle_shutdown(signum, frame):
    """Handle graceful shutdown on SIGTERM/SIGINT"""
    logger.info("Received shutdown signal. Starting graceful shutdown...")
    sys.exit(0)


# Register signal handlers
signal.signal(signal.SIGTERM, handle_shutdown)
signal.signal(signal.SIGINT, handle_shutdown)

if __name__ == "__main__":
    # Parse command line arguments
    parser = argparse.ArgumentParser(description="Run the DeerFlow API server")
    parser.add_argument(
        "--reload",
        action="store_true",
        help="Enable auto-reload (default: True except on Windows)",
    )
    parser.add_argument(
        "--host",
        type=str,
        default="localhost",
        help="Host to bind the server to (default: localhost)",
    )
    parser.add_argument(
        "--port",
        type=int,
        default=8000,
        help="Port to bind the server to (default: 8000)",
    )
    parser.add_argument(
        "--log-level",
        type=str,
        default="info",
        choices=["debug", "info", "warning", "error", "critical"],
        help="Log level (default: info)",
    )

    args = parser.parse_args()

    # Determine reload setting
    reload = False
    if args.reload:
        reload = True

    # Check for DEBUG environment variable to override log level
    if os.getenv("DEBUG", "").lower() in ("true", "1", "yes"):
        log_level = "debug"
    else:
        log_level = args.log_level

    try:
        logger.info(f"Starting DeerFlow API server on {args.host}:{args.port}")
        logger.info(f"Log level: {log_level.upper()}")
        
        # Set the appropriate logging level for the src package if debug is enabled
        if log_level.lower() == "debug":
            logging.getLogger("src").setLevel(logging.DEBUG)
            logging.getLogger("langchain").setLevel(logging.DEBUG)
            logging.getLogger("langgraph").setLevel(logging.DEBUG)
            logger.info("DEBUG logging enabled for src, langchain, and langgraph packages - detailed diagnostic information will be logged")
        
        uvicorn.run(
            "src.server:app",
            host=args.host,
            port=args.port,
            reload=reload,
            log_level=log_level,
        )
    except Exception as e:
        logger.error(f"Failed to start server: {str(e)}")
        sys.exit(1)