Class ChildProcessMonitor

Lib/profiling/sampling/_child_monitor.py:55–279

Monitors a target process for child processes and spawns profilers for them. Use as a context manager: with ChildProcessMonitor(pid, cli_args, output_pattern) as monitor: # monitoring runs here monitor.wait_for_profilers() # optional: wait before cleanup

class ChildProcessMonitor:
    """
    Monitors a target process for child processes and spawns profilers for them.

    Use as a context manager:
        with ChildProcessMonitor(pid, cli_args, output_pattern) as monitor:
            # monitoring runs here
            monitor.wait_for_profilers()  # optional: wait before cleanup
        # cleanup happens automatically
    """

    def __init__(self, pid, cli_args, output_pattern):
        """
        Initialize the child process monitor.

        Args:
            pid: Parent process ID to monitor
            cli_args: CLI arguments to pass to child profilers
            output_pattern: Pattern for output files (format string with {pid})
        """
        self.parent_pid = pid
        self.cli_args = cli_args
        self.output_pattern = output_pattern

        self._known_children = set()
        self._spawned_profilers = []
        self._lock = threading.Lock()
        self._stop_event = threading.Event()
        self._monitor_thread = None
        self._poll_count = 0

    def __enter__(self):
        self._monitor_thread = threading.Thread(
            target=self._monitor_loop,
            daemon=True,
            name=f"child-monitor-{self.parent_pid}",
        )
        self._monitor_thread.start()
        return self

    def __exit__(self, exc_type, exc_val, exc_tb):
        self._stop_event.set()
        if self._monitor_thread is not None:
            self._monitor_thread.join(timeout=2.0)
            if self._monitor_thread.is_alive():
                print(
                    "Warning: Monitor thread did not stop cleanly",
                    file=sys.stderr,
                )

        # Wait for child profilers to complete naturally
        self.wait_for_profilers()

        # Terminate any remaining profilers
        with self._lock:
            profilers_to_cleanup = list(self._spawned_profilers)
            self._spawned_profilers.clear()