Tornado Auto Etag 机制

1def finish(self, chunk: Union[str, bytes, dict] = None) -> "Future[None]":
2        """Finishes this response, ending the HTTP request.
3
4        Passing a ``chunk`` to ``finish()`` is equivalent to passing that
5        chunk to ``write()`` and then calling ``finish()`` with no arguments.
6
7        Returns a `.Future` which may optionally be awaited to track the sending
8        of the response to the client. This `.Future` resolves when all the response
9        data has been sent, and raises an error if the connection is closed before all
10        data can be sent.
11
12        .. versionchanged:: 5.1
13
14           Now returns a `.Future` instead of ``None``.
15        """
16        if self._finished:
17            raise RuntimeError("finish() called twice")
18
19        if chunk is not None:
20            self.write(chunk)
21
22        # Automatically support ETags and add the Content-Length header if
23        # we have not flushed any content yet.
24        if not self._headers_written:
25            if (
26                self._status_code == 200
27                and self.request.method in ("GET", "HEAD")
28                and "Etag" not in self._headers
29            ):
30                self.set_etag_header()
31                if self.check_etag_header():
32                    self._write_buffer = []
33                    self.set_status(304)
34            if self._status_code in (204, 304) or (
35                self._status_code >= 100 and self._status_code < 200
36            ):
37                assert not self._write_buffer, (
38                    "Cannot send body with %s" % self._status_code
39                )
40                self._clear_headers_for_304()
41            elif "Content-Length" not in self._headers:
42                content_length = sum(len(part) for part in self._write_buffer)
43                self.set_header("Content-Length", content_length)
44
45        assert self.request.connection is not None
46        # Now that the request is finished, clear the callback we
47        # set on the HTTPConnection (which would otherwise prevent the
48        # garbage collection of the RequestHandler when there
49        # are keepalive connections)
50        self.request.connection.set_close_callback(None)  # type: ignore
51
52        future = self.flush(include_footers=True)
53        self.request.connection.finish()
54        self._log()
55        self._finished = True
56        self.on_finish()
57        self._break_cycles()
58        return future

1def finish(self, chunk: Union[str, bytes, dict] = None) -> "Future[None]":
2        """Finishes this response, ending the HTTP request.
3
4        Passing a ``chunk`` to ``finish()`` is equivalent to passing that
5        chunk to ``write()`` and then calling ``finish()`` with no arguments.
6
7        Returns a `.Future` which may optionally be awaited to track the sending
8        of the response to the client. This `.Future` resolves when all the response
9        data has been sent, and raises an error if the connection is closed before all
10        data can be sent.
11
12        .. versionchanged:: 5.1
13
14           Now returns a `.Future` instead of ``None``.
15        """
16        if self._finished:
17            raise RuntimeError("finish() called twice")
18
19        if chunk is not None:
20            self.write(chunk)
21
22        # Automatically support ETags and add the Content-Length header if
23        # we have not flushed any content yet.
24        if not self._headers_written:
25            if (
26                self._status_code == 200
27                and self.request.method in ("GET", "HEAD")
28                and "Etag" not in self._headers
29            ):
30                self.set_etag_header()
31                if self.check_etag_header():
32                    self._write_buffer = []
33                    self.set_status(304)
34            if self._status_code in (204, 304) or (
35                self._status_code >= 100 and self._status_code < 200
36            ):
37                assert not self._write_buffer, (
38                    "Cannot send body with %s" % self._status_code
39                )
40                self._clear_headers_for_304()
41            elif "Content-Length" not in self._headers:
42                content_length = sum(len(part) for part in self._write_buffer)
43                self.set_header("Content-Length", content_length)
44
45        assert self.request.connection is not None
46        # Now that the request is finished, clear the callback we
47        # set on the HTTPConnection (which would otherwise prevent the
48        # garbage collection of the RequestHandler when there
49        # are keepalive connections)
50        self.request.connection.set_close_callback(None)  # type: ignore
51
52        future = self.flush(include_footers=True)
53        self.request.connection.finish()
54        self._log()
55        self._finished = True
56        self.on_finish()
57        self._break_cycles()
58        return future