tornado.httpserver — Non-blocking HTTP server

A non-blocking, single-threaded HTTP server.

Typical applications have little direct interaction with the HTTPServer class except to start a server at the beginning of the process (and even that is often done indirectly via tornado.web.Application.listen).

Changed in version 4.0: The HTTPRequest class that used to live in this module has been moved to tornado.httputil.HTTPServerRequest. The old name remains as an alias.

HTTP Server

class tornado.httpserver.HTTPServer(request_callback: Union[httputil.HTTPServerConnectionDelegate, Callable[[httputil.HTTPServerRequest], None]], no_keep_alive: bool = False, xheaders: bool = False, ssl_options: Union[Dict[str, Any], ssl.SSLContext] = None, protocol: Optional[str] = None, decompress_request: bool = False, chunk_size: Optional[int] = None, max_header_size: Optional[int] = None, idle_connection_timeout: Optional[float] = None, body_timeout: Optional[float] = None, max_body_size: Optional[int] = None, max_buffer_size: Optional[int] = None, trusted_downstream: Optional[List[str]] = None)[source]

A non-blocking, single-threaded HTTP server.

A server is defined by a subclass of HTTPServerConnectionDelegate, or, for backwards compatibility, a callback that takes an HTTPServerRequest as an argument. The delegate is usually a tornado.web.Application.

HTTPServer supports keep-alive connections by default (automatically for HTTP/1.1, or for HTTP/1.0 when the client requests Connection: keep-alive).

If xheaders is True, we support the X-Real-Ip/X-Forwarded-For and X-Scheme/X-Forwarded-Proto headers, which override the remote IP and URI scheme/protocol for all requests. These headers are useful when running Tornado behind a reverse proxy or load balancer. The protocol argument can also be set to https if Tornado is run behind an SSL-decoding proxy that does not set one of the supported xheaders.

By default, when parsing the X-Forwarded-For header, Tornado will select the last (i.e., the closest) address on the list of hosts as the remote host IP address. To select the next server in the chain, a list of trusted downstream hosts may be passed as the trusted_downstream argument. These hosts will be skipped when parsing the X-Forwarded-For header.

To make this server serve SSL traffic, send the ssl_options keyword argument with an ssl.SSLContext object. For compatibility with older versions of Python ssl_options may also be a dictionary of keyword arguments for the ssl.SSLContext.wrap_socket method.:

ssl_ctx = ssl.create_default_context(ssl.Purpose.CLIENT_AUTH)
ssl_ctx.load_cert_chain(os.path.join(data_dir, "mydomain.crt"),
                        os.path.join(data_dir, "mydomain.key"))
HTTPServer(application, ssl_options=ssl_ctx)

HTTPServer initialization follows one of three patterns (the initialization methods are defined on tornado.tcpserver.TCPServer):

  1. listen: single-process:

    async def main():
        server = HTTPServer()
        await asyncio.Event.wait()

    In many cases, tornado.web.Application.listen can be used to avoid the need to explicitly create the HTTPServer.

    While this example does not create multiple processes on its own, when the reuse_port=True argument is passed to listen() you can run the program multiple times to create a multi-process service.

  2. add_sockets: multi-process:

    sockets = bind_sockets(8888)
    async def post_fork_main():
        server = HTTPServer()
        await asyncio.Event().wait()

    The add_sockets interface is more complicated, but it can be used with tornado.process.fork_processes to run a multi-process service with all worker processes forked from a single parent. add_sockets can also be used in single-process servers if you want to create your listening sockets in some way other than bind_sockets.

    Note that when using this pattern, nothing that touches the event loop can be run before fork_processes.

  3. bind/start: simple deprecated multi-process:

    server = HTTPServer()
    server.start(0)  # Forks multiple sub-processes

    This pattern is deprecated because it requires interfaces in the asyncio module that have been deprecated since Python 3.10. Support for creating multiple processes in the start method will be removed in a future version of Tornado.

Changed in version 4.0: Added decompress_request, chunk_size, max_header_size, idle_connection_timeout, body_timeout, max_body_size arguments. Added support for HTTPServerConnectionDelegate instances as request_callback.

Changed in version 4.1: HTTPServerConnectionDelegate.start_request is now called with two arguments (server_conn, request_conn) (in accordance with the documentation) instead of one (request_conn).

Changed in version 4.2: HTTPServer is now a subclass of tornado.util.Configurable.

Changed in version 4.5: Added the trusted_downstream argument.

Changed in version 5.0: The io_loop argument has been removed.

The public interface of this class is mostly inherited from TCPServer and is documented under that class.

coroutine close_all_connections() None[source]

Close all open connections and asynchronously wait for them to finish.

This method is used in combination with stop to support clean shutdowns (especially for unittests). Typical usage would call stop() first to stop accepting new connections, then await close_all_connections() to wait for existing connections to finish.

This method does not currently close open websocket connections.

Note that this method is a coroutine and must be called with await.