# Source code for tornado.http1connection

    #
    # Copyright 2014 Facebook
    #
    # Licensed under the Apache License, Version 2.0 (the "License"); you may
    # not use this file except in compliance with the License. You may obtain
    # a copy of the License at
    #
    #     http://www.apache.org/licenses/LICENSE-2.0
    #
    # Unless required by applicable law or agreed to in writing, software
    # distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
    # WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
    # License for the specific language governing permissions and limitations
    # under the License.

    """Client and server implementations of HTTP/1.x.

    .. versionadded:: 4.0
    """

    from __future__ import absolute_import, division, print_function

    import re
    import warnings

    from tornado.concurrent import (Future, future_add_done_callback,
                                    future_set_result_unless_cancelled)
    from tornado.escape import native_str, utf8
    from tornado import gen
    from tornado import httputil
    from tornado import iostream
    from tornado.log import gen_log, app_log
    from tornado import stack_context
    from tornado.util import GzipDecompressor, PY3

    class _QuietException(Exception):
        def __init__(self):
            pass

    class _ExceptionLoggingContext(object):
        """Used with the ``with`` statement when calling delegate methods to
        log any exceptions with the given logger.  Any exceptions caught are
        converted to _QuietException
        """
        def __init__(self, logger):
            self.logger = logger

        def __enter__(self):
            pass

        def __exit__(self, typ, value, tb):
            if value is not None:
                self.logger.error("Uncaught exception", exc_info=(typ, value, tb))
                raise _QuietException

    class HTTP1ConnectionParameters(object):
        """Parameters for `.HTTP1Connection` and `.HTTP1ServerConnection`.
        """
        def __init__(self, no_keep_alive=False, chunk_size=None,
                     max_header_size=None, header_timeout=None, max_body_size=None,
                     body_timeout=None, decompress=False):
            """
            :arg bool no_keep_alive: If true, always close the connection after
                one request.
            :arg int chunk_size: how much data to read into memory at once
            :arg int max_header_size:  maximum amount of data for HTTP headers
            :arg float header_timeout: how long to wait for all headers (seconds)
            :arg int max_body_size: maximum amount of data for body
            :arg float body_timeout: how long to wait while reading body (seconds)
            :arg bool decompress: if true, decode incoming
                ``Content-Encoding: gzip``
            """
            self.no_keep_alive = no_keep_alive
            self.chunk_size = chunk_size or 65536
            self.max_header_size = max_header_size or 65536
            self.header_timeout = header_timeout
            self.max_body_size = max_body_size
            self.body_timeout = body_timeout
            self.decompress = decompress

    class HTTP1Connection(httputil.HTTPConnection):
        """Implements the HTTP/1.x protocol.

        This class can be on its own for clients, or via `HTTP1ServerConnection`
        for servers.
        """
        def __init__(self, stream, is_client, params=None, context=None):
            """
            :arg stream: an `.IOStream`
            :arg bool is_client: client or server
            :arg params: a `.HTTP1ConnectionParameters` instance or ``None``
            :arg context: an opaque application-defined object that can be accessed
                as ``connection.context``.
            """
            self.is_client = is_client
            self.stream = stream
            if params is None:
                params = HTTP1ConnectionParameters()
            self.params = params
            self.context = context
            self.no_keep_alive = params.no_keep_alive
            # The body limits can be altered by the delegate, so save them
            # here instead of just referencing self.params later.
            self._max_body_size = (self.params.max_body_size or
                                   self.stream.max_buffer_size)
            self._body_timeout = self.params.body_timeout
            # _write_finished is set to True when finish() has been called,
            # i.e. there will be no more data sent.  Data may still be in the
            # stream's write buffer.
            self._write_finished = False
            # True when we have read the entire incoming body.
            self._read_finished = False
            # _finish_future resolves when all data has been written and flushed
            # to the IOStream.
            self._finish_future = Future()
            # If true, the connection should be closed after this request
            # (after the response has been written in the server side,
            # and after it has been read in the client)
            self._disconnect_on_finish = False
            self._clear_callbacks()
            # Save the start lines after we read or write them; they
            # affect later processing (e.g. 304 responses and HEAD methods
            # have content-length but no bodies)
            self._request_start_line = None
            self._response_start_line = None
            self._request_headers = None
            # True if we are writing output with chunked encoding.
            self._chunking_output = None
            # While reading a body with a content-length, this is the
            # amount left to read.
            self._expected_content_remaining = None
            # A Future for our outgoing writes, returned by IOStream.write.
            self._pending_write = None

        def read_response(self, delegate):
            """Read a single HTTP response.

            Typical client-mode usage is to write a request using `write_headers`,
            `write`, and `finish`, and then call ``read_response``.

            :arg delegate: a `.HTTPMessageDelegate`

            Returns a `.Future` that resolves to None after the full response has
            been read.
            """
            if self.params.decompress:
                delegate = _GzipMessageDelegate(delegate, self.params.chunk_size)
            return self._read_message(delegate)

        @gen.coroutine
        def _read_message(self, delegate):
            need_delegate_close = False
            try:
                header_future = self.stream.read_until_regex(
                    b"\r?\n\r?\n",
                    max_bytes=self.params.max_header_size)
                if self.params.header_timeout is None:
                    header_data = yield header_future
                else:
                    try:
                        header_data = yield gen.with_timeout(
                            self.stream.io_loop.time() + self.params.header_timeout,
                            header_future,
                            quiet_exceptions=iostream.StreamClosedError)
                    except gen.TimeoutError:
                        self.close()
                        raise gen.Return(False)
                start_line, headers = self._parse_headers(header_data)
                if self.is_client:
                    start_line = httputil.parse_response_start_line(start_line)
                    self._response_start_line = start_line
                else:
                    start_line = httputil.parse_request_start_line(start_line)
                    self._request_start_line = start_line
                    self._request_headers = headers

                self._disconnect_on_finish = not self._can_keep_alive(
                    start_line, headers)
                need_delegate_close = True
                with _ExceptionLoggingContext(app_log):
                    header_future = delegate.headers_received(start_line, headers)
                    if header_future is not None:
                        yield header_future
                if self.stream is None:
                    # We've been detached.
                    need_delegate_close = False
                    raise gen.Return(False)
                skip_body = False
                if self.is_client:
                    if (self._request_start_line is not None and
                            self._request_start_line.method == 'HEAD'):
                        skip_body = True
                    code = start_line.code
                    if code == 304:
                        # 304 responses may include the content-length header
                        # but do not actually have a body.
                        # http://tools.ietf.org/html/rfc7230#section-3.3
                        skip_body = True
                    if code >= 100 and code < 200:
                        # 1xx responses should never indicate the presence of
                        # a body.
                        if ('Content-Length' in headers or
                                'Transfer-Encoding' in headers):
                            raise httputil.HTTPInputError(
                                "Response code %d cannot have body" % code)
                        # TODO: client delegates will get headers_received twice
                        # in the case of a 100-continue.  Document or change?
                        yield self._read_message(delegate)
                else:
                    if (headers.get("Expect") == "100-continue" and
                            not self._write_finished):
                        self.stream.write(b"HTTP/1.1 100 (Continue)\r\n\r\n")
                if not skip_body:
                    body_future = self._read_body(
                        start_line.code if self.is_client else 0, headers, delegate)
                    if body_future is not None:
                        if self._body_timeout is None:
                            yield body_future
                        else:
                            try:
                                yield gen.with_timeout(
                                    self.stream.io_loop.time() + self._body_timeout,
                                    body_future,
                                    quiet_exceptions=iostream.StreamClosedError)
                            except gen.TimeoutError:
                                gen_log.info("Timeout reading body from %s",
                                             self.context)
                                self.stream.close()
                                raise gen.Return(False)
                self._read_finished = True
                if not self._write_finished or self.is_client:
                    need_delegate_close = False
                    with _ExceptionLoggingContext(app_log):
                        delegate.finish()
                # If we're waiting for the application to produce an asynchronous
                # response, and we're not detached, register a close callback
                # on the stream (we didn't need one while we were reading)
                if (not self._finish_future.done() and
                        self.stream is not None and
                        not self.stream.closed()):
                    self.stream.set_close_callback(self._on_connection_close)
                    yield self._finish_future
                if self.is_client and self._disconnect_on_finish:
                    self.close()
                if self.stream is None:
                    raise gen.Return(False)
            except httputil.HTTPInputError as e:
                gen_log.info("Malformed HTTP message from %s: %s",
                             self.context, e)
                if not self.is_client:
                    yield self.stream.write(b'HTTP/1.1 400 Bad Request\r\n\r\n')
                self.close()
                raise gen.Return(False)
            finally:
                if need_delegate_close:
                    with _ExceptionLoggingContext(app_log):
                        delegate.on_connection_close()
                header_future = None
                self._clear_callbacks()
            raise gen.Return(True)

        def _clear_callbacks(self):
            """Clears the callback attributes.

            This allows the request handler to be garbage collected more
            quickly in CPython by breaking up reference cycles.
            """
            self._write_callback = None
            self._write_future = None
            self._close_callback = None
            if self.stream is not None:
                self.stream.set_close_callback(None)

        def set_close_callback(self, callback):
            """Sets a callback that will be run when the connection is closed.

            Note that this callback is slightly different from
            `.HTTPMessageDelegate.on_connection_close`: The
            `.HTTPMessageDelegate` method is called when the connection is
            closed while recieving a message. This callback is used when
            there is not an active delegate (for example, on the server
            side this callback is used if the client closes the connection
            after sending its request but before receiving all the
            response.
            """
            self._close_callback = stack_context.wrap(callback)

        def _on_connection_close(self):
            # Note that this callback is only registered on the IOStream
            # when we have finished reading the request and are waiting for
            # the application to produce its response.
            if self._close_callback is not None:
                callback = self._close_callback
                self._close_callback = None
                callback()
            if not self._finish_future.done():
                future_set_result_unless_cancelled(self._finish_future, None)
            self._clear_callbacks()

        def close(self):
            if self.stream is not None:
                self.stream.close()
            self._clear_callbacks()
            if not self._finish_future.done():
                future_set_result_unless_cancelled(self._finish_future, None)

        def detach(self):
            """Take control of the underlying stream.

            Returns the underlying `.IOStream` object and stops all further
            HTTP processing.  May only be called during
            `.HTTPMessageDelegate.headers_received`.  Intended for implementing
            protocols like websockets that tunnel over an HTTP handshake.
            """
            self._clear_callbacks()
            stream = self.stream
            self.stream = None
            if not self._finish_future.done():
                future_set_result_unless_cancelled(self._finish_future, None)
            return stream

        def set_body_timeout(self, timeout):
            """Sets the body timeout for a single request.

            Overrides the value from `.HTTP1ConnectionParameters`.
            """
            self._body_timeout = timeout

        def set_max_body_size(self, max_body_size):
            """Sets the body size limit for a single request.

            Overrides the value from `.HTTP1ConnectionParameters`.
            """
            self._max_body_size = max_body_size

        def write_headers(self, start_line, headers, chunk=None, callback=None):
            """Implements `.HTTPConnection.write_headers`."""
            lines = []
            if self.is_client:
                self._request_start_line = start_line
                lines.append(utf8('%s %s HTTP/1.1' % (start_line[0], start_line[1])))
                # Client requests with a non-empty body must have either a
                # Content-Length or a Transfer-Encoding.
                self._chunking_output = (
                    start_line.method in ('POST', 'PUT', 'PATCH') and
                    'Content-Length' not in headers and
                    'Transfer-Encoding' not in headers)
            else:
                self._response_start_line = start_line
                lines.append(utf8('HTTP/1.1 %d %s' % (start_line[1], start_line[2])))
                self._chunking_output = (
                    # TODO: should this use
                    # self._request_start_line.version or
                    # start_line.version?
                    self._request_start_line.version == 'HTTP/1.1' and
                    # 1xx, 204 and 304 responses have no body (not even a zero-length
                    # body), and so should not have either Content-Length or
                    # Transfer-Encoding headers.
                    start_line.code not in (204, 304) and
                    (start_line.code < 100 or start_line.code >= 200) and
                    # No need to chunk the output if a Content-Length is specified.
                    'Content-Length' not in headers and
                    # Applications are discouraged from touching Transfer-Encoding,
                    # but if they do, leave it alone.
                    'Transfer-Encoding' not in headers)
                # If connection to a 1.1 client will be closed, inform client
                if (self._request_start_line.version == 'HTTP/1.1' and self._disconnect_on_finish):
                    headers['Connection'] = 'close'
                # If a 1.0 client asked for keep-alive, add the header.
                if (self._request_start_line.version == 'HTTP/1.0' and
                        self._request_headers.get('Connection', '').lower() == 'keep-alive'):
                    headers['Connection'] = 'Keep-Alive'
            if self._chunking_output:
                headers['Transfer-Encoding'] = 'chunked'
            if (not self.is_client and
                (self._request_start_line.method == 'HEAD' or
                 start_line.code == 304)):
                self._expected_content_remaining = 0
            elif 'Content-Length' in headers:
                self._expected_content_remaining = int(headers['Content-Length'])
            else:
                self._expected_content_remaining = None
            # TODO: headers are supposed to be of type str, but we still have some
            # cases that let bytes slip through. Remove these native_str calls when those
            # are fixed.
            header_lines = (native_str(n) + ": " + native_str(v) for n, v in headers.get_all())
            if PY3:
                lines.extend(l.encode('latin1') for l in header_lines)
            else:
                lines.extend(header_lines)
            for line in lines:
                if b'\n' in line:
                    raise ValueError('Newline in header: ' + repr(line))
            future = None
            if self.stream.closed():
                future = self._write_future = Future()
                future.set_exception(iostream.StreamClosedError())
                future.exception()
            else:
                if callback is not None:
                    warnings.warn("callback argument is deprecated, use returned Future instead",
                                  DeprecationWarning)
                    self._write_callback = stack_context.wrap(callback)
                else:
                    future = self._write_future = Future()
                data = b"\r\n".join(lines) + b"\r\n\r\n"
                if chunk:
                    data += self._format_chunk(chunk)
                self._pending_write = self.stream.write(data)
                future_add_done_callback(self._pending_write, self._on_write_complete)
            return future

        def _format_chunk(self, chunk):
            if self._expected_content_remaining is not None:
                self._expected_content_remaining -= len(chunk)
                if self._expected_content_remaining < 0:
                    # Close the stream now to stop further framing errors.
                    self.stream.close()
                    raise httputil.HTTPOutputError(
                        "Tried to write more data than Content-Length")
            if self._chunking_output and chunk:
                # Don't write out empty chunks because that means END-OF-STREAM
                # with chunked encoding
                return utf8("%x" % len(chunk)) + b"\r\n" + chunk + b"\r\n"
            else:
                return chunk

        def write(self, chunk, callback=None):
            """Implements `.HTTPConnection.write`.

            For backwards compatibility it is allowed but deprecated to
            skip `write_headers` and instead call `write()` with a
            pre-encoded header block.
            """
            future = None
            if self.stream.closed():
                future = self._write_future = Future()
                self._write_future.set_exception(iostream.StreamClosedError())
                self._write_future.exception()
            else:
                if callback is not None:
                    warnings.warn("callback argument is deprecated, use returned Future instead",
                                  DeprecationWarning)
                    self._write_callback = stack_context.wrap(callback)
                else:
                    future = self._write_future = Future()
                self._pending_write = self.stream.write(self._format_chunk(chunk))
                self._pending_write.add_done_callback(self._on_write_complete)
            return future

        def finish(self):
            """Implements `.HTTPConnection.finish`."""
            if (self._expected_content_remaining is not None and
                    self._expected_content_remaining != 0 and
                    not self.stream.closed()):
                self.stream.close()
                raise httputil.HTTPOutputError(
                    "Tried to write %d bytes less than Content-Length" %
                    self._expected_content_remaining)
            if self._chunking_output:
                if not self.stream.closed():
                    self._pending_write = self.stream.write(b"0\r\n\r\n")
                    self._pending_write.add_done_callback(self._on_write_complete)
            self._write_finished = True
            # If the app finished the request while we're still reading,
            # divert any remaining data away from the delegate and
            # close the connection when we're done sending our response.
            # Closing the connection is the only way to avoid reading the
            # whole input body.
            if not self._read_finished:
                self._disconnect_on_finish = True
            # No more data is coming, so instruct TCP to send any remaining
            # data immediately instead of waiting for a full packet or ack.
            self.stream.set_nodelay(True)
            if self._pending_write is None:
                self._finish_request(None)
            else:
                future_add_done_callback(self._pending_write, self._finish_request)

        def _on_write_complete(self, future):
            exc = future.exception()
            if exc is not None and not isinstance(exc, iostream.StreamClosedError):
                future.result()
            if self._write_callback is not None:
                callback = self._write_callback
                self._write_callback = None
                self.stream.io_loop.add_callback(callback)
            if self._write_future is not None:
                future = self._write_future
                self._write_future = None
                future_set_result_unless_cancelled(future, None)

        def _can_keep_alive(self, start_line, headers):
            if self.params.no_keep_alive:
                return False
            connection_header = headers.get("Connection")
            if connection_header is not None:
                connection_header = connection_header.lower()
            if start_line.version == "HTTP/1.1":
                return connection_header != "close"
            elif ("Content-Length" in headers or
                  headers.get("Transfer-Encoding", "").lower() == "chunked" or
                  getattr(start_line, 'method', None) in ("HEAD", "GET")):
                # start_line may be a request or response start line; only
                # the former has a method attribute.
                return connection_header == "keep-alive"
            return False

        def _finish_request(self, future):
            self._clear_callbacks()
            if not self.is_client and self._disconnect_on_finish:
                self.close()
                return
            # Turn Nagle's algorithm back on, leaving the stream in its
            # default state for the next request.
            self.stream.set_nodelay(False)
            if not self._finish_future.done():
                future_set_result_unless_cancelled(self._finish_future, None)

        def _parse_headers(self, data):
            # The lstrip removes newlines that some implementations sometimes
            # insert between messages of a reused connection.  Per RFC 7230,
            # we SHOULD ignore at least one empty line before the request.
            # http://tools.ietf.org/html/rfc7230#section-3.5
            data = native_str(data.decode('latin1')).lstrip("\r\n")
            # RFC 7230 section allows for both CRLF and bare LF.
            eol = data.find("\n")
            start_line = data[:eol].rstrip("\r")
            headers = httputil.HTTPHeaders.parse(data[eol:])
            return start_line, headers

        def _read_body(self, code, headers, delegate):
            if "Content-Length" in headers:
                if "Transfer-Encoding" in headers:
                    # Response cannot contain both Content-Length and
                    # Transfer-Encoding headers.
                    # http://tools.ietf.org/html/rfc7230#section-3.3.3
                    raise httputil.HTTPInputError(
                        "Response with both Transfer-Encoding and Content-Length")
                if "," in headers["Content-Length"]:
                    # Proxies sometimes cause Content-Length headers to get
                    # duplicated.  If all the values are identical then we can
                    # use them but if they differ it's an error.
                    pieces = re.split(r',\s*', headers["Content-Length"])
                    if any(i != pieces[0] for i in pieces):
                        raise httputil.HTTPInputError(
                            "Multiple unequal Content-Lengths: %r" %
                            headers["Content-Length"])
                    headers["Content-Length"] = pieces[0]

                try:
                    content_length = int(headers["Content-Length"])
                except ValueError:
                    # Handles non-integer Content-Length value.
                    raise httputil.HTTPInputError(
                        "Only integer Content-Length is allowed: %s" % headers["Content-Length"])

                if content_length > self._max_body_size:
                    raise httputil.HTTPInputError("Content-Length too long")
            else:
                content_length = None

            if code == 204:
                # This response code is not allowed to have a non-empty body,
                # and has an implicit length of zero instead of read-until-close.
                # http://www.w3.org/Protocols/rfc2616/rfc2616-sec4.html#sec4.3
                if ("Transfer-Encoding" in headers or
                        content_length not in (None, 0)):
                    raise httputil.HTTPInputError(
                        "Response with code %d should not have body" % code)
                content_length = 0

            if content_length is not None:
                return self._read_fixed_body(content_length, delegate)
            if headers.get("Transfer-Encoding", "").lower() == "chunked":
                return self._read_chunked_body(delegate)
            if self.is_client:
                return self._read_body_until_close(delegate)
            return None

        @gen.coroutine
        def _read_fixed_body(self, content_length, delegate):
            while content_length > 0:
                body = yield self.stream.read_bytes(
                    min(self.params.chunk_size, content_length), partial=True)
                content_length -= len(body)
                if not self._write_finished or self.is_client:
                    with _ExceptionLoggingContext(app_log):
                        ret = delegate.data_received(body)
                        if ret is not None:
                            yield ret

        @gen.coroutine
        def _read_chunked_body(self, delegate):
            # TODO: "chunk extensions" http://tools.ietf.org/html/rfc2616#section-3.6.1
            total_size = 0
            while True:
                chunk_len = yield self.stream.read_until(b"\r\n", max_bytes=64)
                chunk_len = int(chunk_len.strip(), 16)
                if chunk_len == 0:
                    crlf = yield self.stream.read_bytes(2)
                    if crlf != b'\r\n':
                        raise httputil.HTTPInputError("improperly terminated chunked request")
                    return
                total_size += chunk_len
                if total_size > self._max_body_size:
                    raise httputil.HTTPInputError("chunked body too large")
                bytes_to_read = chunk_len
                while bytes_to_read:
                    chunk = yield self.stream.read_bytes(
                        min(bytes_to_read, self.params.chunk_size), partial=True)
                    bytes_to_read -= len(chunk)
                    if not self._write_finished or self.is_client:
                        with _ExceptionLoggingContext(app_log):
                            ret = delegate.data_received(chunk)
                            if ret is not None:
                                yield ret
                # chunk ends with \r\n
                crlf = yield self.stream.read_bytes(2)
                assert crlf == b"\r\n"

        @gen.coroutine
        def _read_body_until_close(self, delegate):
            body = yield self.stream.read_until_close()
            if not self._write_finished or self.is_client:
                with _ExceptionLoggingContext(app_log):
                    delegate.data_received(body)

    class _GzipMessageDelegate(httputil.HTTPMessageDelegate):
        """Wraps an `HTTPMessageDelegate` to decode ``Content-Encoding: gzip``.
        """
        def __init__(self, delegate, chunk_size):
            self._delegate = delegate
            self._chunk_size = chunk_size
            self._decompressor = None

        def headers_received(self, start_line, headers):
            if headers.get("Content-Encoding") == "gzip":
                self._decompressor = GzipDecompressor()
                # Downstream delegates will only see uncompressed data,
                # so rename the content-encoding header.
                # (but note that curl_httpclient doesn't do this).
                headers.add("X-Consumed-Content-Encoding",
                            headers["Content-Encoding"])
                del headers["Content-Encoding"]
            return self._delegate.headers_received(start_line, headers)

        @gen.coroutine
        def data_received(self, chunk):
            if self._decompressor:
                compressed_data = chunk
                while compressed_data:
                    decompressed = self._decompressor.decompress(
                        compressed_data, self._chunk_size)
                    if decompressed:
                        ret = self._delegate.data_received(decompressed)
                        if ret is not None:
                            yield ret
                    compressed_data = self._decompressor.unconsumed_tail
            else:
                ret = self._delegate.data_received(chunk)
                if ret is not None:
                    yield ret

        def finish(self):
            if self._decompressor is not None:
                tail = self._decompressor.flush()
                if tail:
                    # I believe the tail will always be empty (i.e.
                    # decompress will return all it can).  The purpose
                    # of the flush call is to detect errors such
                    # as truncated input.  But in case it ever returns
                    # anything, treat it as an extra chunk
                    self._delegate.data_received(tail)
            return self._delegate.finish()

        def on_connection_close(self):
            return self._delegate.on_connection_close()

    class HTTP1ServerConnection(object):
        """An HTTP/1.x server."""
        def __init__(self, stream, params=None, context=None):
            """
            :arg stream: an `.IOStream`
            :arg params: a `.HTTP1ConnectionParameters` or None
            :arg context: an opaque application-defined object that is accessible
                as ``connection.context``
            """
            self.stream = stream
            if params is None:
                params = HTTP1ConnectionParameters()
            self.params = params
            self.context = context
            self._serving_future = None

        @gen.coroutine
        def close(self):
            """Closes the connection.

            Returns a `.Future` that resolves after the serving loop has exited.
            """
            self.stream.close()
            # Block until the serving loop is done, but ignore any exceptions
            # (start_serving is already responsible for logging them).
            try:
                yield self._serving_future
            except Exception:
                pass

        def start_serving(self, delegate):
            """Starts serving requests on this connection.

            :arg delegate: a `.HTTPServerConnectionDelegate`
            """
            assert isinstance(delegate, httputil.HTTPServerConnectionDelegate)
            self._serving_future = self._server_request_loop(delegate)
            # Register the future on the IOLoop so its errors get logged.
            self.stream.io_loop.add_future(self._serving_future,
                                           lambda f: f.result())

        @gen.coroutine
        def _server_request_loop(self, delegate):
            try:
                while True:
                    conn = HTTP1Connection(self.stream, False,
                                           self.params, self.context)
                    request_delegate = delegate.start_request(self, conn)
                    try:
                        ret = yield conn.read_response(request_delegate)
                    except (iostream.StreamClosedError,
                            iostream.UnsatisfiableReadError):
                        return
                    except _QuietException:
                        # This exception was already logged.
                        conn.close()
                        return
                    except Exception:
                        gen_log.error("Uncaught exception", exc_info=True)
                        conn.close()
                        return
                    if not ret:
                        return
                    yield gen.moment
            finally:
                delegate.on_close(self)