It still requires explicit action. However, the old way had a little dance between the old process and the new process: the new process tells the old process t

It still requires explicit action. However, the old way had a little dance between the old process and the new process: the new process tells the old process to start shutting down, the old process stops listening for new connections, then the new process starts listening for new connections. That left a gap where connections got rejected. The new technique is for the old process to use a Unix socket to seamlessly transfer ownership of the listening sockets to the new process. At no point are the listening sockets closed, so no connections are rejected. It's still a (potentially) new haproxy binary starting up and parsing the (potentially) changed haproxy config because the user requested a graceful restart.