bpo-29654 : Support If-Modified-Since HTTP header (browser cache) (#298)
Return 304 response if file was not modified.
diff --git a/Doc/library/http.server.rst b/Doc/library/http.server.rst
index fb5c1df..ee1c37c 100644
--- a/Doc/library/http.server.rst
+++ b/Doc/library/http.server.rst
@@ -343,11 +343,13 @@
: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 @@
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
diff --git a/Doc/whatsnew/3.7.rst b/Doc/whatsnew/3.7.rst
index 19e04bb..12f65ff 100644
--- a/Doc/whatsnew/3.7.rst
+++ b/Doc/whatsnew/3.7.rst
@@ -95,6 +95,14 @@
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
------
diff --git a/Lib/http/server.py b/Lib/http/server.py
index 61ddecc..429490b 100644
--- a/Lib/http/server.py
+++ b/Lib/http/server.py
@@ -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 @@
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:
diff --git a/Lib/test/test_httpservers.py b/Lib/test/test_httpservers.py
index 5049538..dafcb0c 100644
--- a/Lib/test/test_httpservers.py
+++ b/Lib/test/test_httpservers.py
@@ -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 @@
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 @@
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 @@
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)
diff --git a/Misc/NEWS b/Misc/NEWS
index a9acaf8..2e9cce6 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -303,6 +303,9 @@
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.