Function _cancel

asyncpg/connect_utils.py:1255–1290

(*, loop, addr, params: _ConnectionParameters,
                  backend_pid, backend_secret)

async def _cancel(*, loop, addr, params: _ConnectionParameters,
                  backend_pid, backend_secret):

    class CancelProto(asyncio.Protocol):

        def __init__(self):
            self.on_disconnect = _create_future(loop)
            self.is_ssl = False

        def connection_lost(self, exc):
            if not self.on_disconnect.done():
                self.on_disconnect.set_result(True)

    if isinstance(addr, str):
        tr, pr = await loop.create_unix_connection(CancelProto, addr)
    else:
        if params.ssl and params.sslmode != SSLMode.allow:
            tr, pr = await _create_ssl_connection(
                CancelProto,
                *addr,
                loop=loop,
                ssl_context=params.ssl,
                ssl_is_advisory=params.sslmode == SSLMode.prefer)
        else:
            tr, pr = await loop.create_connection(
                CancelProto, *addr)
            _set_nodelay(_get_socket(tr))

    # Pack a CancelRequest message
    msg = struct.pack('!llll', 16, 80877102, backend_pid, backend_secret)

    try:
        tr.write(msg)
        await pr.on_disconnect
    finally:
        tr.close()


def _get_socket(transport):