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Revert "Server: Robust shutdown on stdio detach (signals, stdin/paren… #364

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Merged
merged 1 commit into from
Nov 1, 2025
Merged

Revert "Server: Robust shutdown on stdio detach (signals, stdin/paren… #364

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98 changes: 1 addition & 97 deletions MCPForUnity/UnityMcpServer~/src/server.py
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Original file line number Diff line number Diff line change
Expand Up @@ -4,9 +4,6 @@
from logging.handlers import RotatingFileHandler
import os
from contextlib import asynccontextmanager
import signal
import sys
import threading
from typing import AsyncIterator, Dict, Any
from config import config
from tools import register_all_tools
Expand Down Expand Up @@ -67,10 +64,6 @@
# Global connection state
_unity_connection: UnityConnection = None

# Global shutdown coordination
_shutdown_flag = threading.Event()
_exit_timer_scheduled = threading.Event()


@asynccontextmanager
async def server_lifespan(server: FastMCP) -> AsyncIterator[Dict[str, Any]]:
Expand Down Expand Up @@ -193,98 +186,9 @@ def _emit_startup():
register_all_resources(mcp)


def _force_exit(code: int = 0):
"""Force process exit, bypassing any background threads that might linger."""
os._exit(code)


def _signal_handler(signum, frame):
logger.info(f"Received signal {signum}, initiating shutdown...")
_shutdown_flag.set()
if not _exit_timer_scheduled.is_set():
_exit_timer_scheduled.set()
threading.Timer(1.0, _force_exit, args=(0,)).start()


def _monitor_stdin():
"""Background thread to detect stdio detach (stdin EOF) or parent exit."""
try:
parent_pid = os.getppid() if hasattr(os, "getppid") else None
while not _shutdown_flag.is_set():
if _shutdown_flag.wait(0.5):
break

if parent_pid is not None:
try:
os.kill(parent_pid, 0)
except ValueError:
# Signal 0 unsupported on this platform (e.g., Windows); disable parent probing
parent_pid = None
except (ProcessLookupError, OSError):
logger.info(f"Parent process {parent_pid} no longer exists; shutting down")
break

try:
if sys.stdin.closed:
logger.info("stdin.closed is True; client disconnected")
break
fd = sys.stdin.fileno()
if fd < 0:
logger.info("stdin fd invalid; client disconnected")
break
except (ValueError, OSError, AttributeError):
# Closed pipe or unavailable stdin
break
except Exception:
# Ignore transient errors
logger.debug("Transient error checking stdin", exc_info=True)

if not _shutdown_flag.is_set():
logger.info("Client disconnected (stdin or parent), initiating shutdown...")
_shutdown_flag.set()
if not _exit_timer_scheduled.is_set():
_exit_timer_scheduled.set()
threading.Timer(0.5, _force_exit, args=(0,)).start()
except Exception:
# Never let monitor thread crash the process
logger.debug("Monitor thread error", exc_info=True)


def main():
"""Entry point for uvx and console scripts."""
try:
signal.signal(signal.SIGTERM, _signal_handler)
signal.signal(signal.SIGINT, _signal_handler)
if hasattr(signal, "SIGPIPE"):
signal.signal(signal.SIGPIPE, signal.SIG_IGN)
if hasattr(signal, "SIGBREAK"):
signal.signal(signal.SIGBREAK, _signal_handler)
except Exception:
# Signals can fail in some environments
pass

t = threading.Thread(target=_monitor_stdin, daemon=True)
t.start()

try:
mcp.run(transport='stdio')
logger.info("FastMCP run() returned (stdin EOF or disconnect)")
except (KeyboardInterrupt, SystemExit):
logger.info("Server interrupted; shutting down")
_shutdown_flag.set()
except BrokenPipeError:
logger.info("Broken pipe; shutting down")
_shutdown_flag.set()
except Exception as e:
logger.error(f"Server error: {e}", exc_info=True)
_shutdown_flag.set()
_force_exit(1)
finally:
_shutdown_flag.set()
logger.info("Server main loop exited")
if not _exit_timer_scheduled.is_set():
_exit_timer_scheduled.set()
threading.Timer(0.5, _force_exit, args=(0,)).start()
mcp.run(transport='stdio')


# Run the server
Expand Down
98 changes: 1 addition & 97 deletions Server/server.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -4,9 +4,6 @@
from logging.handlers import RotatingFileHandler
import os
from contextlib import asynccontextmanager
import sys
import signal
import threading
from typing import AsyncIterator, Dict, Any
from config import config
from tools import register_all_tools
Expand Down Expand Up @@ -67,10 +64,6 @@
# Global connection state
_unity_connection: UnityConnection = None

# Global shutdown coordination
_shutdown_flag = threading.Event()
_exit_timer_scheduled = threading.Event()


@asynccontextmanager
async def server_lifespan(server: FastMCP) -> AsyncIterator[Dict[str, Any]]:
Expand Down Expand Up @@ -193,98 +186,9 @@ def _emit_startup():
register_all_resources(mcp)


def _force_exit(code: int = 0):
"""Force process exit, bypassing any background threads that might linger."""
os._exit(code)


def _signal_handler(signum, frame):
logger.info(f"Received signal {signum}, initiating shutdown...")
_shutdown_flag.set()
if not _exit_timer_scheduled.is_set():
_exit_timer_scheduled.set()
threading.Timer(1.0, _force_exit, args=(0,)).start()


def _monitor_stdin():
"""Background thread to detect stdio detach (stdin EOF) or parent exit."""
try:
parent_pid = os.getppid() if hasattr(os, "getppid") else None
while not _shutdown_flag.is_set():
if _shutdown_flag.wait(0.5):
break

if parent_pid is not None:
try:
os.kill(parent_pid, 0)
except ValueError:
# Signal 0 unsupported on this platform (e.g., Windows); disable parent probing
parent_pid = None
except (ProcessLookupError, OSError):
logger.info(f"Parent process {parent_pid} no longer exists; shutting down")
break

try:
if sys.stdin.closed:
logger.info("stdin.closed is True; client disconnected")
break
fd = sys.stdin.fileno()
if fd < 0:
logger.info("stdin fd invalid; client disconnected")
break
except (ValueError, OSError, AttributeError):
# Closed pipe or unavailable stdin
break
except Exception:
# Ignore transient errors
logger.debug("Transient error checking stdin", exc_info=True)

if not _shutdown_flag.is_set():
logger.info("Client disconnected (stdin or parent), initiating shutdown...")
_shutdown_flag.set()
if not _exit_timer_scheduled.is_set():
_exit_timer_scheduled.set()
threading.Timer(0.5, _force_exit, args=(0,)).start()
except Exception:
# Never let monitor thread crash the process
logger.debug("Monitor thread error", exc_info=True)


def main():
"""Entry point for uvx and console scripts."""
try:
signal.signal(signal.SIGTERM, _signal_handler)
signal.signal(signal.SIGINT, _signal_handler)
if hasattr(signal, "SIGPIPE"):
signal.signal(signal.SIGPIPE, signal.SIG_IGN)
if hasattr(signal, "SIGBREAK"):
signal.signal(signal.SIGBREAK, _signal_handler)
except Exception:
# Signals can fail in some environments
pass

t = threading.Thread(target=_monitor_stdin, daemon=True)
t.start()

try:
mcp.run(transport='stdio')
logger.info("FastMCP run() returned (stdin EOF or disconnect)")
except (KeyboardInterrupt, SystemExit):
logger.info("Server interrupted; shutting down")
_shutdown_flag.set()
except BrokenPipeError:
logger.info("Broken pipe; shutting down")
_shutdown_flag.set()
except Exception as e:
logger.error(f"Server error: {e}", exc_info=True)
_shutdown_flag.set()
_force_exit(1)
finally:
_shutdown_flag.set()
logger.info("Server main loop exited")
if not _exit_timer_scheduled.is_set():
_exit_timer_scheduled.set()
threading.Timer(0.5, _force_exit, args=(0,)).start()
mcp.run(transport='stdio')


# Run the server
Expand Down
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