Method connection_lost

gunicorn/asgi/protocol.py:672–713

Called when the connection is lost or closed. Instead of immediately cancelling the task, we signal a disconnect event and send an http.disconnect message to the receive queue. This allows the ASGI app to clean up resources (like database connections) gracefully befo

(self, exc)

        self._close_transport()

    def connection_lost(self, exc):
        """Called when the connection is lost or closed.

        Instead of immediately cancelling the task, we signal a disconnect
        event and send an http.disconnect message to the receive queue.
        This allows the ASGI app to clean up resources (like database
        connections) gracefully before the task is cancelled.

        See: https://github.com/benoitc/gunicorn/issues/3484
        """
        # Guard against multiple calls (idempotent)
        if self._closed:
            return

        self._closed = True
        self.worker.nr_conns -= 1

        # Cancel keepalive timer
        self._cancel_keepalive_timer()

        if self.reader:
            self.reader.feed_eof()

        # Signal EOF to WebSocket if active
        if self._websocket:
            self._websocket.feed_eof()

        # Signal disconnect to the app via the body receiver
        if self._body_receiver is not None:
            self._body_receiver.signal_disconnect()

        # Schedule task cancellation after grace period if task doesn't complete
        if self._task and not self._task.done():
            grace_period = getattr(self.cfg, 'asgi_disconnect_grace_period', 3)
            if grace_period > 0:
                self.worker.loop.call_later(
                    grace_period,
                    self._cancel_task_if_pending
                )
            else:
                # Grace period of 0 means cancel immediately
                self._task.cancel()

    def _cancel_task_if_pending(self):
        """Cancel the task if it's still pending after grace period."""