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bpo-29654 : Support If-Modified-Since HTTP header (browser cache) (#298)

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Return 304 response if file was not modified.
This commit is contained in:
Pierre Quentel 2017-04-02 12:26:12 +02:00 • committed by Serhiy Storchaka
parent efbd4ea65d
commit 351adda54b
5 changed files with 112 additions and 9 deletions
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12
Doc/library/http.server.rst
View file

@ -343,11 +343,13 @@ of which this module provides three different variants:
:func:`os.listdir` to scan the directory, and returns a ``404`` error
response if the :func:`~os.listdir` fails.
If the request was mapped to a file, it is opened and the contents are
returned. Any :exc:`OSError` exception in opening the requested file is
mapped to a ``404``, ``'File not found'`` error. Otherwise, the content
If the request was mapped to a file, it is opened. Any :exc:`OSError`
exception in opening the requested file is mapped to a ``404``,
``'File not found'`` error. If there was a ``'If-Modified-Since'``
header in the request, and the file was not modified after this time,
a ``304``, ``'Not Modified'`` response is sent. Otherwise, the content
type is guessed by calling the :meth:`guess_type` method, which in turn
uses the *extensions_map* variable.
uses the *extensions_map* variable, and the file contents are returned.
A ``'Content-type:'`` header with the guessed content type is output,
followed by a ``'Content-Length:'`` header with the file's size and a
@ -360,6 +362,8 @@ of which this module provides three different variants:
For example usage, see the implementation of the :func:`test` function
invocation in the :mod:`http.server` module.
.. versionchanged:: 3.7
Support of the ``'If-Modified-Since'`` header.
The :class:`SimpleHTTPRequestHandler` class can be used in the following
manner in order to create a very basic webserver serving files relative to

8
Doc/whatsnew/3.7.rst
View file

@ -95,6 +95,14 @@ New Modules
Improved Modules
================
http.server
-----------
:class:`~http.server.SimpleHTTPRequestHandler` supports the HTTP
If-Modified-Since header. The server returns the 304 response status if the
target file was not modified after the time specified in the header.
(Contributed by Pierre Quentel in :issue:`29654`.)
locale
------

39
Lib/http/server.py
View file

@ -87,6 +87,9 @@
"SimpleHTTPRequestHandler", "CGIHTTPRequestHandler",
]
import argparse
import copy
import datetime
import email.utils
import html
import http.client
@ -101,8 +104,6 @@
import sys
import time
import urllib.parse
import copy
import argparse
from http import HTTPStatus
@ -686,12 +687,42 @@ def send_head(self):
except OSError:
self.send_error(HTTPStatus.NOT_FOUND, "File not found")
return None
try:
fs = os.fstat(f.fileno())
# Use browser cache if possible
if ("If-Modified-Since" in self.headers
and "If-None-Match" not in self.headers):
# compare If-Modified-Since and time of last file modification
try:
ims = email.utils.parsedate_to_datetime(
self.headers["If-Modified-Since"])
except (TypeError, IndexError, OverflowError, ValueError):
# ignore ill-formed values
pass
else:
if ims.tzinfo is None:
# obsolete format with no timezone, cf.
# https://tools.ietf.org/html/rfc7231#section-7.1.1.1
ims = ims.replace(tzinfo=datetime.timezone.utc)
if ims.tzinfo is datetime.timezone.utc:
# compare to UTC datetime of last modification
last_modif = datetime.datetime.fromtimestamp(
fs.st_mtime, datetime.timezone.utc)
# remove microseconds, like in If-Modified-Since
last_modif = last_modif.replace(microsecond=0)
if last_modif <= ims:
self.send_response(HTTPStatus.NOT_MODIFIED)
self.end_headers()
f.close()
return None
self.send_response(HTTPStatus.OK)
self.send_header("Content-type", ctype)
fs = os.fstat(f.fileno())
self.send_header("Content-Length", str(fs[6]))
self.send_header("Last-Modified", self.date_time_string(fs.st_mtime))
self.send_header("Last-Modified",
self.date_time_string(fs.st_mtime))
self.end_headers()
return f
except:

59
Lib/test/test_httpservers.py
View file

@ -14,11 +14,14 @@
import base64
import ntpath
import shutil
import urllib.parse
import email.message
import email.utils
import html
import http.client
import urllib.parse
import tempfile
import time
import datetime
from io import BytesIO
import unittest
@ -333,6 +336,13 @@ def setUp(self):
self.base_url = '/' + self.tempdir_name
with open(os.path.join(self.tempdir, 'test'), 'wb') as temp:
temp.write(self.data)
mtime = os.fstat(temp.fileno()).st_mtime
# compute last modification datetime for browser cache tests
last_modif = datetime.datetime.fromtimestamp(mtime,
datetime.timezone.utc)
self.last_modif_datetime = last_modif.replace(microsecond=0)
self.last_modif_header = email.utils.formatdate(
last_modif.timestamp(), usegmt=True)
def tearDown(self):
try:
@ -444,6 +454,44 @@ def test_head(self):
self.assertEqual(response.getheader('content-type'),
'application/octet-stream')
def test_browser_cache(self):
"""Check that when a request to /test is sent with the request header
If-Modified-Since set to date of last modification, the server returns
status code 304, not 200
"""
headers = email.message.Message()
headers['If-Modified-Since'] = self.last_modif_header
response = self.request(self.base_url + '/test', headers=headers)
self.check_status_and_reason(response, HTTPStatus.NOT_MODIFIED)
# one hour after last modification : must return 304
new_dt = self.last_modif_datetime + datetime.timedelta(hours=1)
headers = email.message.Message()
headers['If-Modified-Since'] = email.utils.format_datetime(new_dt,
usegmt=True)
response = self.request(self.base_url + '/test', headers=headers)
self.check_status_and_reason(response, HTTPStatus.NOT_MODIFIED)
def test_browser_cache_file_changed(self):
# with If-Modified-Since earlier than Last-Modified, must return 200
dt = self.last_modif_datetime
# build datetime object : 365 days before last modification
old_dt = dt - datetime.timedelta(days=365)
headers = email.message.Message()
headers['If-Modified-Since'] = email.utils.format_datetime(old_dt,
usegmt=True)
response = self.request(self.base_url + '/test', headers=headers)
self.check_status_and_reason(response, HTTPStatus.OK)
def test_browser_cache_with_If_None_Match_header(self):
# if If-None-Match header is present, ignore If-Modified-Since
headers = email.message.Message()
headers['If-Modified-Since'] = self.last_modif_header
headers['If-None-Match'] = "*"
response = self.request(self.base_url + '/test', headers=headers)
self.check_status_and_reason(response, HTTPStatus.OK)
def test_invalid_requests(self):
response = self.request('/', method='FOO')
self.check_status_and_reason(response, HTTPStatus.NOT_IMPLEMENTED)
@ -453,6 +501,15 @@ def test_invalid_requests(self):
response = self.request('/', method='GETs')
self.check_status_and_reason(response, HTTPStatus.NOT_IMPLEMENTED)
def test_last_modified(self):
"""Checks that the datetime returned in Last-Modified response header
is the actual datetime of last modification, rounded to the second
"""
response = self.request(self.base_url + '/test')
self.check_status_and_reason(response, HTTPStatus.OK, data=self.data)
last_modif_header = response.headers['Last-modified']
self.assertEqual(last_modif_header, self.last_modif_header)
def test_path_without_leading_slash(self):
response = self.request(self.tempdir_name + '/test')
self.check_status_and_reason(response, HTTPStatus.OK, data=self.data)

3
Misc/NEWS
View file

@ -303,6 +303,9 @@ Extension Modules
Library
-------
- bpo-29654: Support If-Modified-Since HTTP header (browser cache). Patch
by Pierre Quentel.
- bpo-29931: Fixed comparison check for ipaddress.ip_interface objects.
Patch by Sanjay Sundaresan.